Mcquay Swp 018 User manual

Self-Contained Air Conditioning System

Type SWP 018 through 105

Capacity: 20 to 125 ton

Catalog 860-6

MEA

342-99-E

Contents

McQuay and MicroTech II are registered trademarks of McQuay International. Protocol Selectability is a trademark of McQuay International.

MS-DOS is a registered trademark of Microsoft Corporation. Windows is a trademark of Microsoft Corporation.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

Agency Listed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

Nomenclature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

McQuay Self-Contained VAV Systems . . . . . . . . . . . . . .2

Design Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

Cabinet, Casing, and Frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Condensing Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Cooling Coil Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Heating Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Supply Fan Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Economizer Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Filter Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Acoustic Discharge Plenum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Electrical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

System Flexibility with Unit Options . . . . . . . . . . . . . . . . .8

Selection/Application Flexibility . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

Arrangement Flexibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

Optimal Discharge Air Temperature . . . . . . . . . . . . . . . . . . . . . . . .8

Filtration Flexibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

Acoustic Discharge Plenum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

Energy Saving Economizer Flexibility . . . . . . . . . . . . . . . . . . . . . . .8

Heating Flexibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

Controllers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

Summary of Available Options . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

McQuay MicroTech II Multiple Air Handler Control (MAC) . . . . . . .9

Ultraviolet Lights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

Refrigerant R-407C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

MicroTech II Unit Controller . . . . . . . . . . . . . . . . . . . . . . . .11

Protocol Selectability Feature . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

Main Control Board (MCB) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Cooling Control Boards (CCB) . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Communication Protocol Module (CPM) . . . . . . . . . . . . . . . . . . . 11

Keypad/Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Temperature and Humidity Sensors . . . . . . . . . . . . . . . . . . . . . . 12

Static Pressure Transducers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Zone Temperature Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Stand-alone Controller Features . . . . . . . . . . . . . . . . . . . . . . . . . .12

Internal Time Clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Internal Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

External Time Clock or Tenant Override Input . . . . . . . . . . . . . . . 12

Timed Tenant Override . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Remote Set Point Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Auto/Manual Operation Selection . . . . . . . . . . . . . . . . . . . . . . . . 13

Compressor Lead-lag Selection . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Waterside Economizer Changeover . . . . . . . . . . . . . . . . . . . . . . 13

Airside Economizer Changeover . . . . . . . . . . . . . . . . . . . . . . . . . 13

Cooling and Heating Lockout Control . . . . . . . . . . . . . . . . . . . . . 13

Night Setback and Setup Control . . . . . . . . . . . . . . . . . . . . . . . . . 13

Morning Warm-up Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Condenser Head Pressure Control. . . . . . . . . . . . . . . . . . . . . . . . 14

Outdoor Air Purge Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Proportional Integral Derivative (PID) Control Algorithm . . . . . . . 14

Calibrate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Field Output Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Standard Control Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

Variable Air Volume with Discharge Temperature Control (DAC) 15

Constant Air Volume with Zone Temperature Control (SCC) . . . 15

Constant Air Volume with Discharge Temperature Control (DAC). 15

Discharge Temperature Control . . . . . . . . . . . . . . . . . . . . . . . . . .15

Control Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Proportional Integral Derivative Modulation . . . . . . . . . . . . . . . . . 15

Compressor Staging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Supply Air Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Zone Temperature Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

Control Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Change and Proportional Integral Derivative Modulation . . . . . . 16

Compressor Staging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Project Ahead Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Duct Static Pressure Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

Operating States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

Alarm Management and Control . . . . . . . . . . . . . . . . . . . . . . . . . .18

Application Considerations . . . . . . . . . . . . . . . . . . . . . . . . .19

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

Unit Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

Acoustical Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

Equipment Room . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

Ductwork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

Condenser Water Piping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

Head Pressure Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

Variable Air Volume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

Duct Static Pressure Sensor Placement . . . . . . . . . . . . . . . . . . . .21

Zone Sensor Placement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

Filtration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

System Operating Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

Airflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Fan Heat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Condenser Water Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Coil Freeze Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

Air Density Correction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

Unit Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

Terms of Sale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

Selection Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

Selection Example: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Step 1: Unit Size Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Step 2: Unit DX Cooling Selection . . . . . . . . . . . . . . . . . . . . . . . . 23

Step 3: Economizer Capacity Selection . . . . . . . . . . . . . . . . . . . . 23

Step 4: Heating Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Step 5: Fan/Motor Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Step 6: Calculating Unit Weight . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Step 7: Supply Power Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

R-407C vs. R-22 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Physical Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

Unit Efficiency Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26

Correction Multipliers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

Performance Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28

DX Cooling Capacity Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28

Waterside Economizer Capacity . . . . . . . . . . . . . . . . . . . . . . . . . .36

Heating Capacity Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40

Electric Heat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40

Component Pressure Drops . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41

Fan Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45

Dimensional Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51

Recommended Clearances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .54

Electrical Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55

Supply Power Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57

Unit Weights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .58

Engineering Guide Specifications . . . . . . . . . . . . . . . . . .60

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

Safety Agency Listed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

Cabinet, Casing and Frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

Economizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

Supply Fan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

Cooling Coil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

Heating Coil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

Condensing Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

Refrigeration Capacity Control . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

Acoustic Discharge Plenum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

Electrical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

UV lights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

MicroTech II Unit Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

Open Protocol Communications . . . . . . . . . . . . . . . . . . . . . . . . . 66

McQuay Cat 860-6 1

Introduction

Continued Leadership in System Designs

McQuay SWP Self-Contained air conditioning systems trace

their history to the late 1970s and the pioneering concepts of

Blazer Industries. Working closely with the consulting

engineer to solve special system and space challenges, Blazer

Industries developed and provided the first self-contained,

variable air volume systems with water side economizer cycle

for the prestigious 499 Park Avenue office building in New

York City. Following the success of this project was over a

decade of innovation and product leadership, with more than

thousands of systems provided for prominent building

projects.

Agency Listed

Nomenclature

MEA

368-93-E

Vintage

D = Individual refrigerant circuit, 18–95 tons

E = Individual refrigerant circuit, 105 tons

F = Dual refrigerant circuit

Nominal tons

Self-contained

Water cooled

Plenum discharge

SWP- 055 - F

2McQuay Cat 860-6

McQuay Self-Contained VAV Systems

System performance provides tenant comfort and

operating economy

Since the introduction of self-contained systems in the late

1970s, the industry has seen this concept grow into one of the

most widely specified systems for new office buildings, for

retrofitting existing structures, and for institutional, industrial,

and other specialized applications. The reason is simple:

system performance. McQuay SWP Self-Contained VAV

systems provide the total performance advantage of the

following:

• Tenant comfort

– Tenants enjoy individual control over comfort conditions

and off-hour system operation.

– Tenants benefit from their individual efforts to control

energy costs.

– Routine service is located where it minimizes tenant

inconvenience.

– Individual or dual systems per floor provide system

redundancy and standby.

• First cost economics

– VAV system flexibility uses building diversity to reduce

system tonnage and first cost.

– Factory-packaged concept reduces field labor, installation

time and expense.

– No expensive chilled water piping or chiller room.

– Individually tested, factory-designed systems reduce

startup and installation expense.

– Reduced penthouse and equipment room requirements.

– Centralized condenser water and condensate piping and

streamlined system layout.

• Energy-saving VAV system control

– Reduces fan kW and operating costs at part load

conditions.

– Savings maximized through use of variable speed fan

control.

– Individual zone control without overcooling or use of

reheat.

• Quiet system operation

– Provided by structural quality and specialized design.

– Recognized for quiet operation by renowned U.S.

acoustical consultants.

• Energy saving economizer operation

– Water or air economizer capability for optimized energy

savings.

– Economizer reduces compressor operating hours and

energy costs.

– Year-round “free cooling” capability.

Figure 1: McQuay self-contained VAV systems

• Energy saving building part load operation

– System energy efficiency comparable to central chilled

water systems.

– Multiple systems and compressors versus a single, large

central plant.

– Efficient and reliable system for partial occupancy and

after hours operation.

– Operates only the system(s) on the floor(s) requiring after

hours use.

• System savings of advanced MicroTech II®DDC control

system

– Monitoring and diagnostics reduce the potential for

expensive field repairs.

– Industry leading Protocol Selectability™ feature provides

effective BAS selection flexibility.

• Reduced system maintenance and service costs

– No complicated central chiller plant to maintain.

– Service and maintenance are performed out of the

occupied space.

– Control and product reliability functions designed by the

equipment manufacturer for single source responsibility

and improved reliability.

• System versatility

– Applicable to schools, offices, shopping centers,

manufacturing facilities, etc.

– Prime candidate for floor by floor building renovation.

– Retrofit alternative where existing chiller cannot be

accessed for replacement.

McQuay Cat 860-6 3

McQuay Self-Contained VAV Systems

Design Features

Cabinet, Casing, and Frame

For vibration control and rigging strength, the SWP unit base

is constructed of welded, structural steel channel and 10-gauge

galvanized steel panels. Heavy-duty lifting brackets are

strategically placed for balanced cable or chain hook lifting.

For long equipment life, unit exterior panels are constructed of

heavy gauge, pre-painted, galvanized steel. The complete

cabinet, frame, and access panels are insulated with 1-inch

thick, 1.5 lb. dual density insulation. Double wall construction

is available to enhance performance and satisfy IAQ

requirements.

For maintenance and service ease, system components are

strategically located for ease of inspection and maintenance.

Refrigeration components are positioned out of the airstream

so adjustments and readings can be made without disrupting

system operation. Service-friendly access is made through

heavy-duty, convenient, removable panels. Access panels are

set on neoprene gaskets to prevent air leakage.

Figure 2: SWP cabinet

Condensing Section

Compressors

Multiple compressors and refrigerant circuits are featured in

all SWP systems for efficient system part load control, quiet

operation, and system redundancy. Compressors are quiet,

reliable hermetic scroll or reciprocating type complete with

sightglass, anti-slug protection, and motor overload protection.

The following refrigeration service valves are optional:

•Dual refrigeration circuit units are available with liquid and

discharge line service valves to allow the charge to be

isolated in the condenser.

•

Independent refrigeration circuit units are available with service

valves on both sides of each compressor and filter drier. The

compressor suction and discharge valves include unions to allow

compressors to be replaced without any cutting or brazing.

Individual current-sensing, and temperature-sensing overloads

are provided for each compressor. The unit’s MicroTech II

control system incorporates timing functions to prevent

compressor short cycling. All compressors are resiliently

mounted to minimize any noise transmission. The condensing

section is insulated and segregated from the air handling

section of the unit to avoid transmitting noise to the circulated

air stream.

Refrigerant Circuits

Two refrigerant circuit options are available.

•Four-compressor units are available with two refrigerant

circuits resulting in good reliability and back up, lowest cost,

best part load efficiency, and best value (standard on

four-compressor units).

•Each compressor is supplied with its own independent

refrigerant circuits providing maximum back up and

redundancy (standard on three- and six-compressor units).

Each refrigerant circuit is complete with

•Filter-drier

•Liquid moisture indicator/sightglass

•Thermal expansion valve capable of modulation from 100%

to 25% of its rated capacity gauge ports

•Liquid line shutoff valve with charging port

•High pressure relief device and high and low pressure

cutouts

Hot gas bypass is available on units with two refrigerant circuits.

The unit’s MicroTech II controller senses entering condenser

water temperature and prevents mechanical cooling when the

temperature falls below an adjustable set point value,

minimum 55°F. For systems with entering condenser water

temperatures below 55°F, a waterside economizer or head

pressure activated control valve is available.

Condensers

SWP water-cooled condensers feature a mechanically

cleanable, all copper design using the same high performance

enhanced tubing found in modern centrifugal chillers. Liquid

refrigerant subcooling is provided as standard. Each condenser

is part of an independent refrigerant circuit and comes

complete with a spring-loaded high pressure relief valve. All

condensers are independently leak tested. All completed units

are leak tested, evacuated, and shipped with a full operating

charge of R-22 and oil. R-407C is also available as an alternate

selection.

The condenser assembly and all factory water piping is rated

for a waterside working pressure of 400 psig (200 psig on size

105E with water economizer) and is factory leak tested before

shipment. Condenser water channels are mechanically

cleanable by removing brass service plugs that are sealed with

4McQuay Cat 860-6

McQuay Self-Contained VAV Systems

reusable O-ring gaskets. Main interconnecting condenser

water headers include vent and drain plugs and a large

cleanout plug for removing debris dislodged during cleaning.

Condensers are factory piped for a single condenser water

supply and a single condenser water return connection. Both

right-hand and left-hand piping locations are available.

Cooling Coil Section

SWP evaporator coils incorporate a high efficiency ripple

corrugated fin design. SWP system design maximizes coil face

area without developing uneven, performance-robbing

disruptions in airflow patterns. The result is high coil

performance and reduced static pressure losses.

The evaporator coil is mounted in a stainless steel,

double-sloped drain pan. The condensate drain line is trapped

internally to the unit, eliminating the expense and

inconsistency of field-installed traps.

Figure 3: Evaporator coil circuiting

All evaporator coils are interlaced circuiting, keeping the full

face of the coil active to eliminate air temperature

stratification. For optimum part load performance, all

three-circuit and four-circuit evaporator coils are circuited for

both interlaced and row control. Compressor staging is

sequenced to take maximum advantage of available coil

surface.

Each evaporator coil circuit is furnished with a wide range

thermostatic expansion valve with an adjustable superheat

setting and external equalizer.

Heating Section

SWP units are available as cooling only systems or with

factory-installed electric or hot water heat for morning

warm-up, constant volume, and specialty heating

requirements.

Electric Heat

The factory-assembled electric heating coils are constructed of

low-watt density nickel-chromium elements for long lasting

durability. Electric heaters are protected by automatic reset

high limit controls and line break protection. Heater branch

circuits are protected individually by branch circuit fusing. The

MicroTech II control system sequences the electric heating

elements for operating economy.

Hot Water Heat

Hot water coils have one or two rows with high efficiency

ripple corrugated fin design and 1/2 inch O.D. seamless copper

tubes. Coils are available complete with a factory-mounted,

piped, and wired two-way or modulating valve controlled by

the unit’s MicroTech II controller. A factory-mounted

freezestat is provided to help protect against coil freeze-up.

Supply Fan Section

Figure 4: Supply fan

The supply fan section uses a double width, double inlet,

medium pressure, forward curved or airfoil fan and housing.

Each fan is statically and dynamically balanced. The fan

assembly is constructed of high strength structural steel and

welded for maximum strength. The entire fan assembly is

mounted on spring isolators for excellent isolation

effectiveness. Seismic control restrained spring isolators are

available. A vibration dampening flex connection is installed

at the fan discharge. The entire fan, motor, and drive assembly

is dynamically balanced at the factory for quiet operation.

Forward curved supply fans are configured with a gradual

expansion, aerodynamic duct within the cabinet. This unique

gradual expansion feature contributes to the high performance

of the SWP by lowering brake horsepower and sound power

levels.

All fans are mounted on solid steel shafts rotating in 200,000

hour, pillow block ball bearings with grease fittings. Multiple

belt, fixed pitch sheaves are matched to the specific cfm, static

pressure, and horsepower requirements of the system. Drives

rated for a minimum of 150% of fan design are available.

Drive components and fan bearings are easily accessed for

periodic maintenance.

Fan motors are three phase, NEMA design B, rated at 40°C.

Motor availability includes high efficiency, open, drip-proof,

and totally enclosed selections; EPACT compliant NEMA T-

frame selections; and premium efficiency selections. Motors

are 1800 rpm with grease-lubricated ball bearings.

Refrig. Flow Ckt 1

Refrig. Flow Ckt 2

Ckt 2

Ckt 1

Ckt 2

Airflow

McQuay Cat 860-6 5

McQuay Self-Contained VAV Systems

VAV Control

Energy saving, advanced technology, variable frequency drive

(VFD) fan speed control is available with the convenience and

cost savings of factory mounting and testing. All VFD

selections are plenum rated. A manually activated bypass

contactor is available to allow system operation even in the

event of drive service.

MicroTech II controls provide advanced duct static pressure

control. Static pressure can be controlled by either single or

two-duct static pressure sensors. All VAV systems include an

adjustable, duct high-limit switch to protect duct work from

excessive pressure.

Economizer Options

Waterside Economizer

An energy saving, waterside economizer package is available

on all units. The complete economizer system is factory

mounted including a four-row mechanically cleanable coil,

control valves, and factory piping complete with cleanouts.

The complete economizer package is rated for up to 400 psig

waterside working pressure (200 psig for size 105E), and the

entire coil and piping assembly is factory leak tested.

Economizer operation is controlled by the SWP’s

MicroTech II controller to maximize free cooling potential.

Economizer operation is enabled whenever the available

cooling tower water temperature is less than the unit entering

air temperature by a field-adjustable value, generally 5°F to

7°F. The economizer control valve modulates in response to

the cooling load. Control valve operation can be selected to

maintain full flow through the unit at all times or to isolate the

unit from the condenser water loop when there is no call for

cooling to save energy with a variable pumping system.

(Economizer control valves do not eliminate the need to

provide unit isolation valves.) To extend free cooling savings,

mechanical cooling is enabled during economizer operation.

Only when the economizer valve is driven 90% open and the

cooling load is not satisfied are compressors staged to maintain

cooling set point. Economizer control maintains full, free

cooling capability until disabled by the economizer

changeover set point. A factory-mounted freezestat is provided

to help protect against coil freezeup.

Airside Economizer

An airside economizer control package is available for

controlling field-installed mixing dampers capable of 100%

outside airflow. Economizer operation is controlled by the

SWP’s MicroTech II controller to maximize free cooling

potential. Economizer operation is enabled whenever an

outside air (or comparative) enthalpy sensor or outside air

temperature sensor indicates that outside air is suitable for free

cooling. The economizer damper control actuator modulates in

response to the cooling load. The outside air damper is

positioned to maintain minimum ventilation requirements

when the economizer is disabled.

To extend free cooling savings, mechanical cooling is enabled

during economizer operation. Only when the economizer

damper is driven 90% open and the cooling load is not

satisfied, are compressors staged to maintain cooling set point.

Economizer control maintains full free cooling capability until

disabled by the economizer changeover set point.

Factory-supplied mixing boxes are available for airside

economizer use using the McQuay Vision™ air handling unit

platform.

Condenser Head Pressure Control

For applications where a waterside economizer package is not

being used and entering condenser water temperatures can be

less than 55°F, condenser head pressure control is required. To

satisfy these applications, a factory-installed, two-way, head

pressure activated control valve is available to maintain unit

operation with entering condenser water temperature as low as

40°F.

Figure 5: Mechanically cleanable waterside economizer coil

Figure 6: Economizer piping

6McQuay Cat 860-6

McQuay Self-Contained VAV Systems

Filter Section

All SWP units are provided, as standard, with 4" deep,

extended media, 30% efficient filters. For higher filtration

requirements, 65% and 85% AmericanAirFilterTM Varicel®II

filters are available with an optional pre-filter rack. Filters are

removable from the rear of the unit or through hinged and

latched side access doors on the filter box.

Acoustic Discharge Plenum

To reduce the cost and performance penalties of

field-fabricated duct take-offs and transitions, all SWP units

offer a factory-mounted, acoustically treated discharge plenum

with horizontal duct connections. Custom size duct

connections are available on any side of the plenum and are

configured at the factory prior to shipment. Field cutting of

discharge openings is not required.

The plenum is constructed of prepainted galvanized steel.

Plenum walls are insulated with 3 inches of 3 lb. density glass

fiber insulation, and the entire interior is lined with a 20-gauge,

23% open, perforated galvanized steel liner for added rigidity

and acoustic performance. To reduce turbulence in the plenum

and improve performance, the plenum has acoustic baffles

installed at the plenum corners. Plenums with a single side

discharge opening or a single side with either a front or back

opening have an acoustic baffle isolating the unused portion of

the plenum.

Electrical

Each unit is completely wired and tested at the factory prior to

shipment. Wiring complies with NEC requirements and

conforms to all applicable UL standards for reliability and

safety. All electrical components are labeled according to the

electrical diagram and are UL recognized, whenever

applicable. Line voltage components and wiring are physically

separated from the low voltage control system.

The supply fan motor, compressor motors, and electric heat all

have individual branch circuit, short circuit protection. Control

circuit power is supplied through a factory-installed, low

voltage transformer. The supply fan motor circuit includes a

three-phase contactor and ambient compensated overload

protection with manual reset. Each refrigerant circuit includes

both a high and low pressure cutout switch and a coil frost

protection thermostat.

A terminal block is provided for the single, main power

connection, and a terminal board is provided for low voltage

control wiring. A factory-mounted, non-fused main circuit

interrupter is available for disconnecting the main electrical

power to the unit. The switch is visible, located at the front of

the unit, and is accessible without unit penetration. Dual power

blocks or disconnect switches are available to accommodate

requirements for standby, emergency power supplies.

Controls

MicroTech II Unit Controls

All SWP units feature advanced MicroTech II DDC controls to

provide all temperature and static pressure control, product

reliability, control functions, system time clock, and all

monitoring and diagnostics. Each MicroTech II control system

features a human interface with a 4-line, 20 character display

on the front of the unit for fast system diagnostics and

adjustments. Its easy-to-follow and easy-to-read menus and

data displays encourage and invite the operator to take

advantage of its many capabilities. The complete control

system is factory installed and commissioned prior to

shipment.

Protocol Selectability™ Feature

All MicroTech II control systems have McQuay’s exclusive

Protocol Selectability feature. MicroTech II control systems

can be factory configured for standalone operation or

incorporated into an independent building automation system

using either the BACnet®MS/TP, BACnet®/IP or LonTalk®

protocols. All LonTalk communication is LONMARK 3.3

certified.

Figure 7: Keypad/display panel

McQuay Cat 860-6 7

McQuay Self-Contained VAV Systems

Auxiliary Control Options

Condenser Water Flow Switch.

A factory-installed water

flow sensor is available to verify water flow status at each unit.

Compressor operation is disabled and an alarm signal provided

if condenser water flow is lost. Unit operation is restored when

water flow is sensed again. Water flow status is displayed on

the MicroTech II controls screen.

Freezestat.

A nonaveraging freezestat is available factory

installed on the entering face of the economizer coil. Upon

sensing a potential freeze condition, the unit supply air fan

shuts down, the economizer (and heating) valve drives to the

full open position, and an alarm signal is provided. Unit

operation is restored following manual reset of the freezestat.

Phase Failure/Undervoltage Protection.

Factory-installed

phase failure/under voltage protection is available to protect

three-phase motors from damage due to single phasing, phase

reversal, and low voltage conditions.

Individual Unit Factory Test

All SWP units are completely assembled, piped, wired, and

tested at the factory and shipped in one piece. Each unit

undergoes a factory test that includes:

•Dynamic trim balance of the completed fan assembly

•Run check of all electrical components, alarms, and

shutdowns, including proper control sequencing

•Pressure tests, at rated pressure, of refrigerant coils, water

coils, and condensers prior to assembly

•Final leak checks of the completed refrigerant circuits

•Final leak check of the completed water circuit

•Compressor run check

Verification of factory run test is available at time of unit

shipment.

Figure 8: Test stand

8McQuay Cat 860-6

System Flexibility with Unit Options

Along with providing high quality and state-of-the-art

innovation, SWP self-contained systems offer customized

flexibility to satisfy a wide range of diverse applications.

Selection/Application Flexibility

Nominal cooling capacities range from 20 to 125 tons. In

addition, all units offer multiple compressor selections to meet

exacting system requirements. Over 130 different standard

compressor/coil capacity selections are available. The

flexibility to optimize the self-contained system to fit the

application is a McQuay SWP advantage. Available system

applications include the following:

•VAV discharge air temperature control with static pressure

control

•Discharge air temperature control with constant air volume

•Constant volume, zone temperature control

•100% outside air control

•Dehumidification control, with or without reheat control

In addition to compressor/coil flexibility, SWP systems offer

double width, double inlet, forward curved fans with

factory-mounted variable frequency drives for maximizing

VAV system fan performance. High efficiency fan capability

coupled with extensive compressor flexibility provide the right

system selection for the application.

Arrangement Flexibility

All SWP systems offer the flexibility of right-hand and

left-hand piping arrangements and front and rear fan discharge

orientations. Piping and fan arrangement flexibility can

simplify mechanical equipment room arrangement, improve

installation costs, and improve total system performance.

Optimal Discharge Air Temperature

More and more system engineers are designing optimal

discharge air temperature systems to improve system

performance and system first cost; the McQuay SWP provides

the flexibility to do it successfully. Optimal discharge air

temperature systems are designed to provide unit leaving air

temperature selections of 52°F to 53°F versus more

conventional systems that supply air at temperatures closer to

58°F. This five to six degree reduction in air temperature to the

room diffusers can subsequently reduce the required supply air

volume to the room by 20% to 25%.

The benefits of optimal discharge air temperature systems

become quite apparent with a look at the advantages offered

with reduced supply air cfm airflow:

•Reduced first cost and installation cost by allowing smaller

duct sizes and a smaller air distribution system.

•Reduced bhp requirements. Depending on changes in duct

size and the resulting total static pressure, a 20% reduction in

supply air cfm can reduce fan bhp requirements by 25% or

more.

•Reduced fan sound power generation and a quieter room

environment.

•Reduced equipment room size may be possible due to using

a physically smaller unit size.

Filtration Flexibility

SWP systems are offered with 4-inch, 30% efficient, pleated

filters as standard. Also available are 4-inch, 65% efficient,

pleated filters and 4-inch, 85% efficient filters with prefilters.

Acoustic Discharge Plenum

While others may provide a simple multidirectional discharge

plenum, SWP systems feature a multidirectional plenum with

true acoustic design qualities.

The following SWT plenum features provide not only

application flexibility but also the acoustic performance not

found in simple, single-wall plenums:

•Heavy-gauge galvanized steel construction

•3-inch, 3-lb., glass fiber thermal/acoustic insulation

•An inner, perforated galvanized steel acoustic liner

•Internal acoustic baffles

Energy Saving Economizer Flexibility

To improve system operating performance, all SWP systems

offer complete factory-mounted and factory-controlled

waterside economizer capability. Each waterside economizer

system includes a 4-row, mechanically cleanable coil with

dual, 2-way control valves to allow use in either a constant or

variable volume pumping system. In addition, units can be

applied with air economizer cycles with integrated factory

control.

Heating Flexibility

A variety of heating media is offered with each SWP system.

Hot water coils with modulating valve and actuator are

available along with staged electric heat to provide heating

control in a variety of applications.

Controllers

MicroTech II DDC control systems provide constant volume,

variable air volume, 100% outside air, and/or dehumidification

control flexibility. See “Controls” on page 6 for more

information.

McQuay Cat 860-6 9

System Flexibility with Unit Options

Summary of Available Options

•Over 130 different compressor/coil capacity selections

•Multiple control options: VAV, CV, 100% OA,

dehumidification

•Nonfused main power disconnect switch

•Dual nonfused main disconnect switches

•Nonaveraging freezestat for hot water or waterside

economizer coil protection

•Unit phase failure/under voltage protection

•Premium efficiency fan motors

•TEFC fan motors

•Condenser water flow switch

•4-row waterside economizer system

•Air cycle economizer system

•Modulating hot water heat

•Staged electric heat

•Multi direction, acoustic discharge plenum

•Factory-mounted and factory-controlled variable frequency

drives

•High efficiency filtration options

•Right-hand and left-hand piping selections

•Front and back fan discharge arrangements

•Head pressure control valve

•Special coil coatings

•Double wall cabinet construction

•Seismic fan isolation

•UV lights

•Two refrigerant circuit options

– Dual refrigerant circuit units offer the following options:

• Three-row or five-row DX coils with enhanced heat

transfer surfaces

• Hot gas bypass on one refrigerant circuit

• Discharge and liquid line shut off valves for each

circuit

– Independent refrigerant circuit units offer the following

options:

• Four-row or six-row DX coils with standard heat

transfer surfaces

• R-407C or R-22

• Shut off valves on each side of each filter drier/sight

glass assembly

• Roto-lock suction and discharge service and shut off

valves on each compressor

McQuay MicroTech II Multiple Air Handler

Control (MAC)

The MicroTech II Multiple Air Handler Control (MAC)

provides control coordination for multiple units serving a

common space or feeding a common ductwork system.

The MAC manages each group of units to operate in concert.

Individual unit controls cannot reliably handle parallel units

because the controls fight each other at part load. Inevitably,

one unit overpowers the other.

Benefits of Parallel Units on a Common Duct

•Improved system reliability as units and sensors can provide

redundancy if a sensor on a unit requires maintenance.

•Lower first cost from increased diversity resulting in lower

installed tonnage.

•Lower installed cost due to fewer roof penetrations and less

floor-to-floor ductwork.

•Improved space temperature control from smaller cooling

stages relative to load and reduced compressor cycling.

Ultraviolet Lights

Factory-installed ultraviolet lights are available on the

downstream side of all cooling coils and above the unit drain pan.

All ultraviolet lights are pre-engineered and factory installed

for ease of use and proper placement for maximum

effectiveness. The ultraviolet lamps irradiate the coil and drain

pan surfaces with light in the 245 nanometer wavelength of the

light spectrum (UV-C). UV-C light has proven effective in

killing most bacteria, molds, and viruses in both laboratory and

practical application. This complete package of equipment and

ultraviolet lights includes Intertek Services Inc. (ETL) safety

agency certification.

Features

•High-output, hot cathode lamps produce ultraviolet

germicidal irradiation (UVGI) for 254 nm that constantly

irradiates the coil and drain pan surfaces.

•Fixture design and stainless steel construction make the

ultraviolet light device suitable for saturated air conditions.

•Automatic disconnects are standard on all doors (or panels)

with line-of-sight access to the lamps to help prevent eye

contact with the UV-C ultraviolet light.

•Special ultraviolet filtering glass windows block ultraviolet

light, allowing the coil, drain pan, and lights to be inspected

while in use from outside the unit.

10 McQuay Cat 860-6

System Flexibility with Unit Options

Benefits

•For pennies a day, UVGI can improve IAQ by destroying

mold, fungi, and bacteria on coil and drain pan surfaces.

•Clean coil surfaces maintain peak heat transfer for “near

new” performance and lower energy costs.

•Reduced coil and drain pan maintenance requirements and

costs.

•Satisfies GSA federal facilities standard requirements for

UVGI lights to be incorporated downstream of all cooling

coils and above all drain pans to control airborne and surface

microbial growth and transfer.

Figure 9: Ultraviolet light

Refrigerant R-407C

McQuay SWP units with independent refrigerant circuits are

available with non-ozone depleting R-407C refrigerant. R-407C

refrigerant is better for the environment than R-22 (see the note

below).

Note – In response to the Montreal Protocol, the United States

EPA announced that R-22 production/imports will be

limited starting January 1, 2010, likely ending R-22 use in

all new equipment. After January 1, 2020, domestic R-22

production/imports will cease and all service work will

require recycled R-22 refrigerant or a replacement such

as R-407C.

Given the many inherent differences in oil, operating

pressure, and control settings between R-22 and the HFC

alternatives, future conversion of an R-22 system to an

HFC is likely to be difficult and costly.

Features

•HFC-407C refrigerant is environmentally friendly with zero

ozone depleting allowance (ODP).

•ASHRAE Standard 34, Designation and Safety

Classification of Refrigerants, classifies HFC-407C as an A1

(lower toxicity—no flame propagation) refrigerant.

•Units are factory engineered for proper cooling performance

using R-407C.

•Units are factory charged with R-407C and synthetic oil

(such as POE), and they include components and controls

specifically tailored to R-407C.

•Units are factory tested prior to shipment

Benefits

•HFC-407C allows you to provide your tenants with a

comfortable building environment in an environmentally

friendly way.

•With no phase out date for production of HFC-407C, a

reliable supply should be available for the life of your

equipment.

•Fully engineered and factory tested units with R-407C avoid

the downtime, high costs, and risk associated with a field

conversion of an R-22 system to an R-407C.

McQuay Cat 860-6 11

MicroTech II Unit Controller

Designed with the system operator in mind, McQuay SWP

systems continue to provide industry leading performance,

featuring the microprocessor-based MicroTech II

Self-Contained System Unit Control system. In addition to

providing stable, efficient temperature, and static pressure

control, the controller is capable of providing comprehensive

diagnostics, alarm monitoring, and alarm specific component

shutdown if critical equipment conditions occur.

A user interface featuring an 8-key keypad and a

4-line × 20-character display comes as standard with each

MicroTech II control system, providing system operators with

superior access to temperatures, pressures, operating states,

alarm messages, set points, control parameters, and schedules.

All messages are displayed in easy-to-follow text. Password

protection is included to protect against unauthorized or

accidental set point or parameter changes.

Protocol Selectability Feature

MicroTech II unit control systems are factory configured for

either standalone operation or for incorporation into

independent building automation systems (BAS) through our

Protocol Selectability feature. By using industry recognized

communication protocols, BACnet MS/TP®, BACnet®/IP or

LonTalk®, McQuay MicroTech II controls expand the horizon

of opportunities for BAS choice without sacrificing system

performance.

BACnet communications conform to the BACnet Standard,

ANSI/ASHRAE Standard 135-2001 and are supported by a

protocol implementation conformance statement (PICS).

LonTalk communications are in accordance with either the

Discharge Air Controller (DAC) or Space Comfort Controller

(SCC) profiles and are LONMARK 3.3 certified.

The building automation system can interact with one or

multiple self-contained unit controllers in the following ways:

•Set the unit’s operating and occupancy modes

•Monitor all controller inputs, outputs, set points, parameters,

and alarms

•Set controller set points and parameters

•Clear alarms

•Reset the cooling and heating discharge air temperature set

point (DAC units)

•Reset the duct static pressure set point (DAC units)

•Set the heat/cool changeover temperature

•Set the representative zone temperature (SCC units)

Components

Each SWP self-contained system is equipped with a complete

MicroTech II unit control system that is pre-engineered,

preprogrammed, and factory tested prior to shipment. Each of

the MicroTech II unit control systems is composed of several

components that are individually replaceable for ease of

service. These components include:

•Keypad/display user interface

•Main control board

•Cooling control board(s)

•Communication protocol module (optional)

•Pressure transducers

•Unit-mounted temperature sensors

•Zone temperature sensor packages

•Humidity sensor

Main Control Board (MCB)

The main control board (MCB) contains a microprocessor that

is preprogrammed with the software necessary to control the

unit. This provides that schedules, set points and parameters

are not lost, even during a long-term power outage. The

microprocessor board processes system input data and then

determines and controls output responses. An RS-232

communication port is provided as standard to allow for direct

or modem access with a PC-based service tool.

Cooling Control Boards (CCB)

A cooling control board (CCB) is used to expand the input and

output capability of the main control board (MCB). Each CCB

communicates with the MCB via serial data communications.

These microprocessor based boards provide independent

operation and alarm response even if communication is lost

with the MCB.

Communication Protocol Module (CPM)

The communication protocol module (CPM) provides the

means to factory or field configure MicroTech II unit controls

for interoperability with an independent BAS using McQuay’s

innovative Protocol Selectability feature. Communication

protocol modules are available to support industry recognized

communication protocols including BACnet MS/TP,

BACnetIP, and LonTalk.

12 McQuay Cat 860-6

MicroTech II Unit Controller

Keypad/Display

All MicroTech II controllers include a keypad/display that

provides user interface with the main control board (MCB). The

keypad/display has eight, easy-to-use, touch-sensitive membrane

key switches that are used for positioning the display and

entering changes. The display is a supertwist nematic type with

highly visible black characters on a yellow background. The

4-line × 20-character format allows for easy-to-understand

display messages. All operating conditions, system alarms,

control parameters, and schedules can be monitored from the

keypad/display. If the correct password is entered, any adjustable

parameter or schedule can be modified from the keypad.

Figure 10: MicroTech II keypad/display

Temperature and Humidity Sensors

With the exception of the return air sensor and zone sensor, all

temperature sensors are factory installed and tested. Return air

sensors are factory tested but require field installation in the

return air duct. Zone sensor packages are available to suit any

application. When required for dehumidification applications,

a humidity sensor is available for field installation.

Static Pressure Transducers

All pressure transducers are factory installed and tested.

Connection and routing of sampling tubes is done at time of

unit installation.

Zone Temperature Sensors

Two types of optional zone temperature sensors are available

for use with the MicroTech II controller:

•Zone sensor with tenant override switch.

•Zone sensor with tenant override switch and remote set point

adjustment.

Timed tenant override is a standard MicroTech II control feature.

Zone sensors are required to utilize the controller’s purge

cycle, space reset of supply air set point, and night setback, or

setup features (see following). All zone sensors are field

installed with field wiring terminated at a separate, clearly

marked terminal strip.

Stand-alone Controller Features

MicroTech II self-contained system unit controls include all of

the essential features required to make them capable of

completely independent, stand-alone operation.

Internal Time Clock

An internal, battery-backed time clock is included with each

MicroTech II unit controller. Current date and time can be set

quickly and easily at the user interface keypad.

Internal Schedule

Seven daily schedules and one holiday schedule can be entered

at the keypad of all unit controllers. For each of these eight

schedules, one start and one stop time can be entered. Up to 16

holiday periods of any duration can be designated. The unit

automatically runs according to the holiday schedule on

holiday dates. To handle special occasions, use an additional

“one event” schedule.

In lieu of its internal schedule, the unit can be operated

according to a network schedule from the BAS.

External Time Clock or Tenant Override Input

An input is supplied that can be used to accept a field-wired

start/stop signal from a remote source. An external time clock,

a tenant override switch, or both, can be connected. Whenever

the external circuit is closed, the controller overrides the

internal schedule (if activated) and places the unit into the

occupied mode.

If the internal schedule or a BAS network schedule is used,

field wiring is not required.

Timed Tenant Override

Off-hour operation flexibility is a must in today’s office

environments; standalone MicroTech II controllers handle it

with ease. When unit operation is desired during unoccupied

hours, initiate timed tenant override by pressing the tenant

override button on either of the optional zone sensor packages.

The unit then starts and runs in the occupied mode for a keypad

adjustable length of time (up to five hours). If the button is

pressed again while the unit is operating, the timer resets to the

full time allowance without interrupting unit operation. Tenant

override operation also can be initiated by the BAS.

Remote Set Point Adjustment

All constant air volume-zone temperature control (SCC) unit

controllers include an input that can be used to remotely adjust

the zone cooling and heating set points. To use this feature,

wire the optional zone sensor package with set point

adjustment to the controller. The remote set point adjustment

feature can be enabled or disabled from the keypad at any

time. When enabled, the remote set point adjustment is

available even if the return temperature is selected to be the

Control Temperature.

McQuay Cat 860-6 13

MicroTech II Unit Controller

Auto/Manual Operation Selection

Automatic or manual operation can be controlled either

remotely or at the keypad.

All controllers include two inputs that can be used to enable or

disable cooling, heating, and fan operation from remote switches.

With the “heat enable” and “cool enable” terminals, the operator

can enable cooling, heating, or both. Using the system “off”

terminals, the operator can disable the fans, and thus the entire

unit, so that the unit cannot be started remotely.

From the keypad, a variety of occupancy and auto/manual

control mode selections are available to the operator:

•Occupancy modes

– Auto

– Occupied

– Unoccupied

– Tenant override

•Control modes

–Off

– Auto

– Heat/cool

– Cool only

– Heat only

–Fanonly

Compressor Lead-lag Selection

All unit controllers are capable of automatic compressor,

lead-lag control. If automatic control is not desired, the

operator can disable the compressor lead-lag function.

Waterside Economizer Changeover

On units equipped with a waterside economizer package, the

MicroTech II unit controller includes an internal changeover

strategy that compares entering cooling tower water temperature

to the unit’s mixed air temperature. If the entering water

temperature is less than the mixed air temperature by a

field-adjustable differential (typically 5°F to 7ºF), the economizer

control valve modulates in response to the cooling load.

Airside Economizer Changeover

On units equipped with airside economizer control (control

only, economizer mixing dampers by others), there are two

methods of determining whether the outdoor air is suitable

for free cooling: one method senses enthalpy (dry bulb

temperature and humidity) and one senses outdoor air dry

bulb temperature.

The enthalpy changeover method uses an external control

signal wired to a designated controller input.

All unit controllers include an internal changeover strategy

that can be selected at the keypad. When this method is

selected, the controller compares the outdoor air dry-bulb

temperature, provided by the optional outdoor air temperature

sensor, to a keypad programmable set point. The external

enthalpy control input then is ignored.

Cooling and Heating Lockout Control

All unit controllers include a keypad programmable set point for

locking out mechanical cooling when the entering tower water

temperature is below the lockout set point. The factory default

set point is 55ºF. The default is adjustable to a minimum of 50ºF

when a waterside economizer package is used. For systems

without a waterside economizer, an optional head pressure

regulating valve is required for operation below 55ºF.

When an economizer system is used, mechanical cooling is

locked out whenever the economizer is enabled and the

economizer position is less than 90%. This energy saving

feature requires that full economizer potential be used before

mechanical cooling is allowed to energize.

Night Setback and Setup Control

When one of the available zone temperature sensors is

connected to the unit controller, night setback heating and

night setup cooling control are available. Separate, keypad

programmable, night heating and cooling set points are used to

start the unit when necessary. After the unit starts, night

setback and setup control is similar to normal occupied control

except that the minimum outside air damper position is set to

zero. If the outside air is suitable for free cooling, and an

airside economizer is used, outside air is used during night

setup operation.

Except for 100% outside air applications, night setback control

is available even if the unit is not equipped with any heating

equipment. When the space temperature falls to the night

setback set point, the fan starts and runs until the temperature

rises above the differential. This feature may be useful for

applications that use duct-mounted heating coils.

Morning Warm-up Control

If the space temperature is below set point when the unit enters

the occupied mode, the morning warm-up control function

keeps the outside air dampers closed while heat is supplied to

satisfy set point. The outside air damper remains closed until

either the space temperature rises to the heating set point or the

keypad adjustable morning warm-up timer expires (default is

90 minutes). The morning warm-up timer provides that the

minimum required amount of outdoor air is supplied after a

certain time, regardless of the space temperature.

Morning warm-up control is automatically included on all

units except 100% outside air units. It is available even if the

unit is not equipped with any heating equipment for

applications that use duct mounted heating coils.

14 McQuay Cat 860-6

MicroTech II Unit Controller

Condenser Head Pressure Control (units without

waterside economizer only)

Mechanical cooling is allowed whenever the entering cooling

tower water temperature is 55ºF or warmer, without the use of

head pressure control. When the entering water temperature is

below 55ºF, a factory-installed and factory-controlled two-way

modulating head pressure control valve can be utilized. The

regulating valve is controlled by the MicroTech II controller to

maintain refrigerant head pressure.

Outdoor Air Purge Control (units with airside

economizer only)

Purge control is designed to take advantage of cool early

morning outside air conditions. It starts the fans and modulates

the economizer dampers to maintain occupied cooling

requirements during unoccupied periods, if conditions are

appropriate. This provides the opportunity to flush the space

with fresh outdoor air prior to occupancy. Purge operation is

possible only during a keypad-adjustable time window prior to

occupancy (0 to 240 minutes). When the purge-cycle is active,

mechanical cooling is disabled. To use the purge feature,

connect one of the zone temperature sensors to the unit

controller. Below is a description of purge control operation.

During the purge time window, the unit starts and runs

whenever these three requirements are met:

•The space temperature must be warm enough to enable

occupied cooling.

•The outside air enthalpy must be low enough to enable the

economizer.

•The outside air temperature must be at least 3°F less than the

space temperature.

When any one of these conditions is no longer true, the unit

shuts down. As conditions allow, purge cycles the unit in this

manner until it enters the occupied mode.

Proportional Integral Derivative (PID) Control

Algorithm

The proportional integral derivative (PID) control algorithm

controls modulating actuators to maintain a measured variable

(temperature or pressure) at or near its set point. For example, it

controls economizer actuators to maintain the discharge cooling

set point, and it controls the supply fan variable frequency

drives to maintain the duct static pressure set point. The integral

control feature effectively eliminates “proportional droop” (load

dependent offset) resulting in the tightest possible control.

For each PID loop, five keypad-adjustable parameters allow

the control loop to be properly tuned for any application:

•Period

•Dead band

•Proportional band

•Integral time

•Derivative time

Appropriate default values for these parameters are loaded into

each controller. These default values provide proper control for

most applications; therefore, field tuning usually is not

required and start-up time is reduced.

Change Algorithm.

The PID function is also used to adjust set

points instead of controlling variable speed drives or actuators

directly. For example, in zone control applications, the PID

loop automatically “changes” the discharge temperature set

point (cooling or heating) as the Control Temperature deviates

from the zone set point. Another PID loop then controls the

economizer actuator or heating valve actuator using the current

discharge temperature set point. Unlike a typical

“master-submaster” reset strategy, this “cascade control”

continuously adjusts the discharge set point, even if the Control

Temperature’s deviation from set point remains constant. This

means that the unit’s cooling or heating output is set according

to the actual load, not just the current zone temperature. The

tightest possible zone temperature control results because

“proportional droop” (load dependent offset) is eliminated.

Calibrate

When initiated at the keypad by an operator, the Calibrate

function automatically calibrates all actuator position feedback

inputs and all pressure transducer inputs. It does this by

shutting the unit down and then driving all actuators to the full

closed and full open positions. The controller records the input

voltage values that correspond to these positions. The pressure

transducer input voltages, which are assumed for 0.00" wc,

also are recorded. When Calibrate finishes, enter an operator

command at the keypad to start the unit. The Calibrate feature

can reduce start-up time and assist in periodic maintenance.

Field Output Signals

All MicroTech II controllers include four solid-state relay

outputs that are available for field connection to any suitable

device: remote alarm output, fan operation output, outside air

damper output, and pump start output. On VAV units, an

additional VAV box output is also available. These five outputs

are used to signal field equipment of unit status.

Remote alarm output:

Use to operate a 24-volt relay to

provide a remote alarm signal to a light, audible alarm, or

other device when an alarm condition exists at the unit.

Fan operation output:

Use to control field equipment that

depends on fan operation, for instance, to open field-installed

isolation dampers or VAV boxes. To allow actuators enough

time to stroke, the fan operation output energizes three minutes

before the fans start. It remains energized until thirty seconds

after the unit airflow switch senses no airflow. The fan

operation output is on whenever the unit airflow switch senses

airflow.

Outside Air Damper output:

Use to signal an outside air

damper actuator to open whenever the unit is in an occupied

cooling or heating condition.

VAV box output:

Provides a means of interfacing the unit and

the VAV box control. When the output is energized (closed), the

McQuay Cat 860-6 15

MicroTech II Unit Controller

VAV output indicates that the unit is in the cooling mode. When

de-energized (open), it indicates that the unit is either providing

heat or circulating air to equalize temperature conditions just

after start-up (this is the Recirculate operating state). On units

with single stage “morning warm-up” heat, the open VAV box

output contact is meant to provide a signal to drive the boxes

wide open. To prevent duct over-pressurization, fan variable

speed drives or inlet vanes are driven to a minimum position

before the output’s contacts de-energize again for normal

cooling operation (Post Heat operating state).

Pump Start output:

Use to provide a start/stop signal to the

cooling tower circulating pump. The pump start output is on

whenever fan operation and cooling is required.

Standard Control Options

SWP Self-Contained systems are available for most any

constant or variable air volume application. MicroTech II

controls offer three basic control configurations that use

sophisticated state change control logic to provide stable,

reliable and efficient control:

•

Variable air volume with discharge temperature control (DAC)

•Constant air volume with zone temperature control (SCC)

•

Constant air volume with discharge temperature control (DAC)

When combined with MicroTech II’s many available control

capabilities, both factory-installed and keypad-programmable,

these three basic configurations can be customized to meet the

requirements of the most demanding applications.

Variable Air Volume with Discharge Temperature

Control (DAC)

All VAV units provide true discharge temperature control in

addition to duct static pressure control. Cooling only, cooling

with single-stage “morning warm-up” heat, and cooling with

modulating heat configurations are available.

Constant Air Volume with Zone Temperature Control

(SCC)

SCC units are available in either cooling only or cooling with

modulating heat configurations. Either of these configurations

is available for 100% recirculated, mixed, or 100% outdoor air

applications.

Constant Air Volume with Discharge Temperature

Control (DAC)

DAC units are available in cooling only, cooling with

single-stage “morning warm-up” heat, or cooling with

modulating heat configurations. This unit configuration can be

used for applications that have zone controlled terminal heating

coils or for constant volume, 100% outdoor air applications.

The discharge temperature control strategies used with the

hybrid DAC unit are identical to those used with the DAC unit.

Discharge Temperature Control

MicroTech II DAC controllers provide sophisticated and

flexible discharge air temperature control that is only possible

with DDC systems. Separate discharge air temperature set

points are used for cooling and modulating heating control. At

the keypad, the operator can enter either the desired set points

or select separate reset methods and parameters for each set

point. See “Supply Air Reset” on page 16.

Control Temperature

The Control Temperature makes the heat/cool changeover

decision. It determines whether cooling or heating is enabled.

The discharge temperature then determines whether cooling or

heating is actually supplied. At the keypad, the operator can

choose the source of the Control Temperature from among the

following:

•Space temperature sensor

•Return temperature sensor

•Outside air temperature sensor (modulating heat only)

•Network communication

The operator enters separate cool and heat enable set points

and deadbands to which the Control Temperature is

compared (see Figure 11). When the Control Temperature is

greater than or equal to the cooling set point, cooling is

enabled. When the Control Temperature is less than or

equal to the heat set point, heating is enabled. If desired,

these set points and differentials can be set so there is a

dead band in which both cooling and heating are disabled.

The controller’s software prevents simultaneous cooling

and heating.

Figure 11: Control temperature—discharge temperature

control

Proportional Integral Derivative Modulation

When operating in economizer free cooling or unit heating, the

previously described PID algorithm maintains discharge

temperature control. The PID algorithm provides precise

control of the economizer dampers, modulating gas heat,

steam or hot water valves.

16 McQuay Cat 860-6

MicroTech II Unit Controller

Compressor Staging

Two staging algorithms are available to control a unit’s

multiple steps of capacity control: “Average” and “Nearest.”

These control algorithms provide reliable discharge

temperature control while managing compressor cycling rates.

Constraints on compressor staging are essential for preventing

short cycling, which can reduce compressor life by causing

improper oil return and excessive heat buildup in the motor

windings.

The “Average” compressor staging algorithm keeps track of

the discharge temperature and stages cooling up or down to

maintain an average temperature that is equal to the effective

discharge cooling set point. A stage change can occur only

•After the keypad adjustable inter-stage timer expires (five

minute default setting)

•If the discharge temperature is outside a keypad programmed

dead band (see Figure 12).

After these two conditions are met, staging occurs as the

controller attempts to equalize two running totals: degree-time

above set point and degree-time below set point. The result is

that the average discharge temperature is maintained at the

cooling set point.

The “Nearest” compressor staging algorithm keeps track of the

discharge temperature and stages cooling up or down to

maintain it as closely as possible to the set point. A stage

change can occur only

•After the keypad adjustable inter-stage timer expires (five

minute default setting)

•If the control logic calculates that a stage change will result

in a discharge temperature closer to set point than the

existing condition.

The controller logic continually calculates the expected effect

of a stage change and uses this information before making a

change. A change is made only if it brings the discharge

temperature closer to set point, resulting in a more consistent

discharge temperature, reduced compressor cycling, and more

stable VAV box control.

Figure 12: Compressorized discharge air cooling

Supply Air Reset

Supply air reset can increase the energy efficiency of VAV

systems by automatically varying the discharge air temperature

to suit a building’s cooling or heating needs. MicroTech II

controllers offer a variety of different reset strategies that can

be selected at the keypad. Because they are keypad

programmable, reset strategies can be changed or eliminated as

desired. Separate strategies can be selected for cooling and for

modulating heat. If reset is not desired, a fixed discharge

cooling or heating set point can be entered.

The following reset methods are available:

•Space temperature

•Return temperature

•Outdoor air temperature

•Supply airflow (VAV, cooling set point only)

•External 1–5 VDC or 4–20 mA signal

•Network communication

For all temperature reset methods, the minimum and maximum

cooling and heating set points are keypad programmable along

with the corresponding minimum and maximum space, return

or outdoor air temperature parameters. For the supply airflow

method, the discharge set point is reset as the supply fan

modulates between 30% and 100%. For the external method,

the discharge set point is reset as the voltage or current signal

varies over its entire range. For units in a BAS network, the

discharge set points are reset via the communication signal.

Zone Temperature Control

The MicroTech II SCC control system provides the

sophisticated and flexible zone temperature control that is only

possible with DDC systems. Zone temperature sensors are

available with or without a remote set point adjustment. With

the remote adjustment model, the space set point can be set at

the keypad or at the zone sensor package. (Even if a zone

sensor is connected, remote set point adjustment can be

enabled or disabled as desired at the keypad.)

Control Temperature

Control Temperature is the representative zone temperature.

When compared with the zone set points, it determines

whether the unit supplies heating or cooling, or neither. It also

determines the amount of cooling or heating required to satisfy

the load. Its source, selected at the keypad, is either the zone

temperature sensor or the return temperature sensor

The Control Temperature is the primary input to the

MicroTech II zone temperature control algorithms. Figure 11

on page 15 shows the parameters with which the Control

Temperature is compared to control the cooling or heating

output. The functions of these parameters are described below.

The controller’s software prevents cooling and heating from

being enabled at the same time.

Change and Proportional Integral Derivative

Modulation

When economizer “free” cooling or unit heating is required,

the two MicroTech II PID loops combine to provide cascade

control, the tightest possible zone temperature control. By

controlling the discharge temperature and the zone

temperature, these functions eliminate temperature variations

near the diffusers, which can occur with traditional zone

control due to its inherent lag effect.

McQuay Cat 860-6 17

MicroTech II Unit Controller

Change:

If the Control Temperature is above or below the set

point by more than the dead band, the Change PID loop adjusts

the cooling or heating discharge air temperature set point as

necessary. The amount of this set point change corresponds to

the Control Temperature’s position in the modulation range.

The farther the Control Temperature is from the set point, the

greater the change. Set point changes are limited to ranges

defined by keypad-programmable maximum and minimum

values.

PID:

The PID function uses the Change function’s current

discharge set point to maintain precise discharge temperature

control by modulating the economizer dampers and gas heat,

steam or hot water heating valves.

Compressor Staging

Compressor staging is controlled directly by the Control

Temperature. When the Control Temperature is warmer than

the zone cooling set point, cooling is staged up; when the

Control Temperature is cooler than the zone cooling set point,

cooling is staged down. However, a stage change can occur

only when the Control Temperature is outside the dead band.

Staging is constrained by an inter-stage delay timer (5-minute

default setting) and minimum and maximum discharge air

temperature limits (all keypad programmable). These

constraints protect the compressors from short cycling while

eliminating temperature variations near the diffusers.

Project Ahead Algorithm

The inherent lag effect in zone temperature control

applications can cause overshoot during warm-up or

cool-down periods. MicroTech II features a unique “Project

Ahead” control algorithm that eliminates this overshoot by

calculating the rate at which the Control Temperature is

changing and reducing the unit’s cooling or heating output as

the zone temperature nears its set point. A separate,

keypad-programmable Project Ahead time parameter provides

fine tuning for both heating and cooling.

Duct Static Pressure Control

On all DAC units, duct static pressure control is maintained by

the PID algorithm, which provides precise control of the

supply fan variable frequency drive or inlet vanes. The

keypad-programmable set point can be set between 0.20'' wc

and 4.00" wc.

An optional second duct static sensor is available for larger

buildings with multiple trunk runs or large shifts in load due to

solar effects (east/west building orientation). The MicroTech II

controller automatically selects and uses the lower of the two

sensed pressures to control fan volume. This feature provides

that adequate static pressure is supplied to the most demanding

space at all times.

Multiple Unit Applications

For applications in which multiple units are connected in a

common duct system, it is important to control all units as

described in “McQuay MicroTech II Multiple Air Handler

Control (MAC)” on page 9.

Operating States

Operating states define the current overall status of the

self-contained system. At the user interface, the operator can

display the current operating state and thereby quickly assess

the unit’s operating condition. Figure 13 shows all the possible

operating states and the status information they summarize.

Depending on unit options, some operating states may not

apply. For example, a 100% outside air unit does not have a

Morning Warm-Up, Economizer, or Unoccupied Economizer

operating state.

Figure 13: Operating state sequence chart

Fan only

Economizer

UnocEcon

UnocClg Cooling

Heating

MWU

Min DAT

Recirculate

Startup

UnocHtg

OffAny State

18 McQuay Cat 860-6

MicroTech II Unit Controller

Alarm Management and Control

MicroTech II unit controllers are capable of sophisticated

alarm management and controlled response functions. Each

alarm that occurs is prioritized, indicated, and responded to

with the appropriate action. The current alarm (up to four

alarms, arranged by alarm priority) and previous alarm (up to

eight alarms, arranged by date/time cleared), each with a time

and date stamp, can be displayed at the user interface.

Whenever a current alarm is cleared, it is logged as a previous

alarm and all events in memory are shifted. The current alarm

becomes the new previous alarm, and the oldest previous

alarm is removed.

Alarm Priority

The various alarms that can occur are prioritized according to

the severity of the problem. See Table 1. Three alarm

categories are used: faults, problems, and warnings.

1Faults are the highest priority alarms. If a fault condition

occurs, the complete unit shuts down until the alarm

condition is gone and the fault is manually cleared at the

keypad. A fault example is Fan Fail alarm.

2Problems are the next lower priority to alarms. If a

problem occurs, the complete unit does not shut down, but

its operation is modified to compensate for the alarm

condition. A problem automatically clears when the alarm

condition that caused it is gone. Compressor Fail is an

example of a problem where only the affected compressor

is shut down.

3Warnings are the lowest priority alarms. No control action

is taken when a warning occurs; it is indicated to alert the

operator that the alarm condition needs attention. To make

sure that they are read, the operator must manually clear all

warnings. Dirty Filter indication is an example of a

warning.

Generally, a specific alarm condition generates an alarm that

falls into only one of these categories. Under different sets of

circumstances, however, the freezestat and most of the sensor

failure alarm conditions can generate alarms that fall into

multiple categories.

Adjustable Alarm Limits.

Four alarm indications have

adjustable limits that are used to trigger the alarm. The high

return temperature alarm and the high and low supply

temperature alarms are adjusted at the user interface. The dirty

filter alarm(s) is adjusted at the sensing device.

Personal Computer Based ServiceTools™

A personal computer (PC) can be equipped with Windows

-based

Service Tools

™

software to provide a high level operator interface

with the MicroTech II unit controls for expanded diagnostic and

service capability. The PC can be connected directly to the

MicroTech II controller or used remotely with the addition of an

optional unit-mounted phone modem.

Table 1: MicroTech II alarm summary

Alarm Name Fault Problem Warning

Freeze X X

Smoke X

Temperature Sensor Fail X X

Duct High Limit X

High Return Temp X

High Discharge Temp X

Low Discharge Temp X

Fan Fail X

Fan Retry X

Discharge Air Capacity Feedback X

Economizer Stuck X X

Auxiliary Control Board Enable X

Auxiliary Control Board

Communications X

Low Airflow X

Heat Fail X

Circuit 1–6 High Pressure X

Circuit 1–6 Low Pressure/Frost X

Compressor 1–6 Motor Protection X

Compressor 1–6 Fail X

Auxiliary Control Board Enable

Hardware X

Airflow Switch (False Airflow) X

Dirty Filter X

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