Dunham-Bush ACXi 165-5SP-LN User manual

Form No: MM0418A
- Mesa Hospital, Ankara, Turkey
AIR COOLED
ROTARY
SCREW
CHILLERS
INSTALLATION,
OPERATION AND
MAINTENANCE
MANUAL
INSTALLATION,
OPERATION AND
MAINTENANCE
MANUAL
MODEL:
ACXi 165-5SP-LN
50 Hz
50 Hz50 Hz
Products That Perform...By people Who Care
R

TABLE OF CONTENTS
DESCRIPTION PAGE NO DESCRIPTION PAGE NO
1.0 INTRODUCTION
1.1 Product Identification.......................................3
2.0 INSTALLATION
2.1 General .............................................................5
2.1.1 ApplicationPrecautions...............................5
2.1.2 Chilled Water Flow.....................................5
2.2 Inspection.........................................................5
2.3 Rigging..............................................................5
2.3.1 General......................................................5
2.3.2 Rigging & Moving......................................5
2.4 Space Requirements and Clearance ..............7
2.4.1 General......................................................7
2.4.2 ACXi.........................................................7
2.5 Foundation .....................................................10
2.6 Vibration Isolation ........................................10
2.7 Piping connections.........................................10
2.8 Electrical Wiring...........................................10
2.9 Controls..........................................................12
2.9.1 Connections.............................................12
2.9.2 Settings....................................................12
2.10 Request For Start-Up Representative .........12
3.0 OPERATION
3.1 General ...........................................................13
3.2 Unit piping......................................................13
3.3 System Water Flow Rate...............................13
3.4 Standard Ambient Unit Operation (65°F
Minimum Ambient) Including Overnight
Shut Down and Morning Restart 13
3.4.1 Air Cooled Package Chiller Start-Up ..........13
3.5 System Start Up..............................................13
3.6 Shut-Down (Overnight Or Weekend)..........16
3.7 Seasonal Shut-Down Procedure ...................16
3.8 Seasonal Start-up Procedure ........................16
3.9 Safety Relief Valves.......................................17
3.10 Refrigeration Cycle- Multiple
Compressor ACXi..........................................17
3.11 Fan Cycling ....................................................17
3.12 Liquid Injection .............................................17
3.13 Hydraulic Capacity Control System............17
4.0 ELECTRICAL
4.1 Electrical Data ...............................................19
4.2 Wiring Diagram.............................................19
4.3 Typical Operation..........................................19
4.4 Microcomputer Controller...........................32
4.4.1 To Display Data from the Menu.................32
4.4.2 To Reset All Control Points To
Computer Control.....................................32
4.4.3 To Display Alarms....................................32
4.4.4 To Become Authorized..............................32
4.4.5 To Alter Setpoint Data...............................32
4.4.6 To Calibrate Temperature and
Pressure Sensors.......................................33
4.4.7 To Set Data and Time................................33
4.4.8 To Display Data without Accessing Menu...33
4.4.9 Unit Schedule of Operation........................33
4.5 Control Functions..........................................34
4.5.1 Chilled Water Pump Interlock And
Flow Switch (CWP And CWFS).................34
4.5.2 Customer Interlock....................................35
4.5.3 Anti-Recycle Timer (Microcomputer).........35
4.5.4 Load Control (Microcomputer)...................35
4.5.5 Ramp Control (Microcomputer)..................35
4.5.6 Current Limiting (Microcomputer)..............36
4.5.7 Staging Control (Microcomputer)...............36
4.5.8 Manual lead-Lag Control (Microcomputer)..36
4.5.9 Manual Load-Unload Control
(Microcomputer).......................................36
4.5.10Chilled Water Reset and Customer
Control Interlock (Optional).......................37
4.5.11Variable Fan Speed Control (Optional)........37
4.5.12Sump Heater Control.................................37
4.6 Safety Functions.............................................37
4.6.1 Control Power Loss (Microcomputer).........37
4.6.2 Low Pressure Cut-Off (Microcomputer) ......37
4.6.3 Evaporator Freeze Shutoff (Microcomputer) 37
4.6.4 HighPressure Cut-Off (Microcomputer)......37
4.6.5 Oil Level Switch (FS)................................38
4.6.6 Overload Protector (OL) ............................38
4.6.7 Phase Control Relay (PCR)........................38
4.6.8 SensorAlarm(Microcomputer) ..................38
4.6.9 No-Stop Alarm (Microcomputer)................38
4.6.10Low Differential Pressure Alarm
(Microcomputer).......................................38
5.05.0 MAINTENANCE
5.1 General ............................................................39
5.2 Periodic Inspection ........................................39
5.3 Monthly Inspection ........................................39
5.4 Vessel Maintenance .......................................39
5.4.1 general.....................................................39
5.4.2 Water Side Cleaning of Evaporator.............39
5.5 Air Cooled Condenser Cleaning...................39
5.6 Electrical Malfunction...................................41
5.7 Refrigerant Charge........................................41
5.7.1 General....................................................41
5.7.2 Air Cooled Packages.................................41
5.8 Oil Charge ......................................................41
5.9 Troubleshooting.............................................42
5.10 Sample Log Sheet...........................................43
SCHEMATIC DIAGRAM, GRAPH AND TABLE
DESCRIPTION PAGE NO
Figure 2.3.2 ACXi 165-5SP-LN Typical Rigging.....................6
Figure 2.4.1 ACXi 165-5SP-LN Space Requirements...............7
Figure 2.4.2 ACXi 165-5SP-LN Dimensional Data...................9
Figure 2.5A ACXi 165-5SP-LN Isolator Location..................11
Figure 2.5B ACXi 165-5SP-LN Isolator Point Load Data.......11
Figure 3.2 ACXi 165-5SP-LN Typical Piping Schematic......14
Figure 3.3 EvaporatorWaterPressureDrop........................15
Figure 3.13 Compressor Capacity Control Detail...................18
Figure 4.2 ACXi 165-5SP-LN Typical Wiring Schematic.....20
DESCRIPTION PAGE NO
Table1.1 Physical Specifications........................................4
Table4.5.5 Sample Ramp Times (Minutes) For Two
Compressor Unit ...............................................36
Table5.4.2 R407cPressure/TemperatureProperties...............40
- 2 -

1.0 INTRODUCTION
This manual is prepared to provide all the necessary information for
installation, operation and maintenance of the latest generation of the
Dunham-Bush medium screw compressor air-cooled packaged chillers.
To use this manual effectively, you must first identify your unit model
from the unit nameplate.
Your Dunham-Bush chiller has been manufactured under a careful
quality control system. If the package is installed, operated and
maintained with care and attention to the instructions contained herein,
it will give many years of satisfactory service.
It is assumed those who use of this manual and those who install,
operate and maintain this equipment are experienced and qualified air
conditioning equipment personnel.
1.1 PRODUCT IDENTIFICATION
ACXi100 5QPLN
Air Cooled
Packaged Chiller
Screw
Compressor
Vapor Injection
Nominal Tons
S-Standard
Q-Special
5-50Hz
6-60Hz
Blank -R22
P-R407C
R-R134a
Low Noise
- 3 -

1.0 INTRODUCTION
TABLE 1.1 PHYSICAL SPECIFICATIONS
Model ACXi 165-5SP-LN
Compressor
Model ( Qty. ) MSC 1210(1), 1212 (1)
RPM 2950
Oil Charge Liter (Qty) 37.3(1), 33.5 (2)
% Unit Capacity Reduction (Min.) 100 – 25%
Evaporator
Model EXD16112J07DFRO
Water Connections ( inch / mm ) 6 / 152
Nom. Water Flow ( GPM ) / PD (ft.wg.) 402.4 / 19.8
Min. / Max. Water Flow ( GPM ) 197.5 / 481.6
Min. / Max. Water Flow PD ( ft.wg. ) 6.1 / 30.0
Air Cooled Condenser
Coil Rows Deep / FA ( Sq.Ft ) 3 / 141.2, 3 / 141.2
No. Of Fans 6, 6
Fan Diameter ( inch / mm ) 31.5 / 800.0, 31.5 / 800.0
Motor HP ( Each ) 0.5, 0.5
Min. Ambient Temperature °F @ Min. Load 65 °F
General
Unit Length (inch / mm ) 322 1/2 / 8191
Unit Width ( inch / mm ) 88 / 2235
Unit Height ( inch / mm ) 96 / 2438
Shipping Weight ( lb / kg ) 15915 / 7219
Operating Weight ( lb / kg ) 16333 / 7409
Operating Charge R407c ( lb / kg ) 437 / 198
- 4 -

2.0 INSTALLATION
2.1 GENERAL
Packaged chillers are designed to cool water or
other non-corrosive liquids. Water is circulated
through the direct expansion evaporator where it
is cooled to the desired temperature then
circulated to cooling coils for air conditioning, or
to other types of heat exchangers for process
cooling.
Care should be taken to see that the equipment is
properly installed and adjusted. An installer or
operator should first become familiar with the
information contained in this manual.
2.1.1 APPLICATION PRECAUTIONS
The following instructions are intended to
help assure proper and successful
application of your water chilling
machine.
2.1.2 CHILLED WATER FLOW
The Dunham-Bush ACXi Packaged
Water Chiller is designed for a constant
chilled water flow rate, even when the
cooling load is varying. The machine will
generally perform satisfactorily with
steady flow rates deviating from design
by as much as ±10%. However, varying
water flow rates can cause control
instability which will result in undesirable
system effects, particularly poor control
of leaving chilled water temperature. If
two-way valves are used to control flow
through cooling coils, some means such
as an automatic modulating valve should
be provided in the system to maintain
steady flow through the evaporator.
If the chilled water system is arranged for
the dual purpose of cooling and heating,
the evaporator must incorporate valves to
prevent the flow of hot water through it.
This can be done with either manual or
automatic shutoff valves, but the method
of control must be that water temperature
entering the evaporator never exceeds
90°F.
2.2 INSPECTION
When the equipment is delivered, it is important
that the following inspection be completed in the
presence of the carrier's representative.
1.) Check all crates and cartons received against
the Bill of Lading/Shipping Papers to be sure
they agree.
2.) Check the model number and the electrical
characteristics on the nameplate to determine
if they are correct.
3.) Check for freight damage, shortages or other
discrepancies and note them on the delivery
receipt before signing.
In the event that any damage is found, a damage
claim should immediately be filed by the
purchaser against the delivering carrier as all
shipments are F.O.B. Factory.
2.3 RIGGING
2.3.1 GENERAL
Each unit has been carefully tested and
crafted at the factory where every
precaution is taken to assure that the unit
reaches you in perfect condition. It is very
important that the riggers and movers
should use the same care and precaution
in moving the equipment into place. Make
sure that chains, cables. or other moving
equipment are placed so as to avoid
damage to the unit or piping. The
refrigerant piping must not be used as a
ladder or as a hand hold. Do not attach a
chain hoist sling to the piping or
equipment. Move the unit in an upright
position and let it down gently from
trucks or rollers.
2.3.2 RIGGING AND MOVING
Any unit mounted on skids may be moved
with a forklift, but care must be taken not
to damage the unit with forks. The skids
should not be removed until the unit is at
its final location.
The ACXI model is to be rigged through
the holes in the base side rails. In all
cases, spreader bars must be used between
rigging lines to prevent coil or fan deck
damage. The unit must be lifted using All
Rigging Points. Refer to Rigging
Instructions on Figure 2.3.2.
All models can be pushed or pulled (with
chains) from the control box end only.
Truck forks must be kept level and not
tilted back. Do not raise the end of the
unit more than 2" off the floor.
- 5 -

2.0 INSTALLATION
FIGURE 2.3.2 ACXi 165-5SP-LN TYPICAL RIGGING
- 6 -

2.0 INSTALLATION
2.4 SPACE REQUIREMENTS
AND CLEARANCE
2.4.1 GENERAL
The dimensional data and clearances that
follow are useful for determining space
requirements. The unit should be placed
to make the clearance noted available for
servicing properly. Failure to allow these
clearances will cause serious trouble and
result in higher costs for operation,
maintenance and repair.
2.4.2 ACXi
The dimensional data are shown in
Figure 2.4.2 and space requirements are
shown in Figure 2.4.1. The most
important consideration which must be
taken into account when deciding upon
location of air cooled equipment, is
provision for a supply of ambient air to
the condenser, and removal of heated air
from the condenser area. Where this
essential requirement is not provided, it
will result in higher condensing
temperatures, which cause poor
operation, higher power consumption
and possibly, eventual failure of
equipment. Units must not be located in
the vicinity of steam, hot air or fume
exhausts.
Another consideration which must be
taken into account is that the unit should
be mounted away from noise sensitive
spaces and must have adequate support
to avoid vibration and noise transmission
into the building. Units should be
mounted over corridors, utility areas, rest
rooms or other auxiliary areas where
sound levels are not an important factor.
Sound and structural consultants should
be retained for recommendations on
critical installations.
FIGURE 2.4.1 ACXI 165-5SP-LN SPACE REQUIREMENTS
WALLS OR OBSTRUCTIONS
The unit should be located so that air may circulate freely and not be recirculated. For proper air flow
and access all sides of the unit must be a minimum of four feet away from any wall or obstruction. It is
preferred that this distance be increased whenever possible. Care should be taken to see that ample
room is left for maintenance work through access doors and panels. Overhead obstructions are not
permitted. When the unit is in an area where it is enclosed by three walls the unit must be installed as
indicated for units in a pit.
- 7 -

2.0 INSTALLATION
FIGURE 2.4.1 ACXi 165-5SP-LN SPACE REQUIREMENTS
Single Pit ( See Note 2 )
Double Pit ( See Note 2 )
Multi Pit
Corner Wall Notes
1.) All Dimensions Are Minimal, Unless
Otherwise Noted.
2.) Pit Installations Are Not Recommended.
Re-Circulation Of Hot Condenser Air In
Combination With Surface Air Turbulence
Cannot Be Predicted. Hot Air Re-
Circulation Will Severely Affect Unit
Efficiency (EER) And Can Cause High
Pressure Or Fan Motor Temperature
Trips. Dunham-Bush Will Not Be
Responsible For Ducting Fans To A
Higher Level To Alleviate The Above
Mentioned Conditions.
- 8 -

2.0 INSTALLATION
FIGURE 2.4.2 ACXi 165-5SP-LN DIMENSIONAL DATA
NOTE: ALL DIMENSIONS ARE IN INCHES [MM].
- 9 -

2.0 INSTALLATION
2.5 FOUNDATION
Refer to index for unit dimensions and load
points. Foundations must be level for proper
operation and functioning of controls and
provision must be made for supporting the
individual load points as shown in the unit
dimensions. Roof mounted units must be
supported on adequate steel structure. If units are
located on the ground level, a concrete base is
recommended.
2.6 VIBRATION ISOLATION
Under certain critical conditions. it may be
necessary to install vibration isolators under the
base of the packaged chiller.
Rubber-in-shear or spring vibration isolators are
offered as optional items. When spring isolators
are used, flexible connections must be installed
in the water piping system and in the refrigerant
lines of split systems. Note: These flexible
connectors must be suitable for the fluid and
pressures involved.
All piping which is external to the packaged
chiller must be supported by spring mounted
hangers and any piping which goes through the
wall, ceiling or floor should be properly sheathed
to prevent transmission of piping vibration to the
structure.
When spring isolators are used, electrical service
to the unit must also be flexibly connected by
means of a 36" section of flexible conduit.
2.7 PIPING CONNECTIONS
Refer to the dimensional drawings for water
piping connection locations. After the unit has
been leveled and isolators (if any) installed &
adjusted, connect evaporator water piping,
keeping in mind that the evaporator tubes may
require cleaning or replacement at some future
date, and removable sections of piping will be
required to permit evaporator head removal.
Piping must be supported to avoid excess stress
on the evaporator heads. Cut piping holes in the
removable access panel at the end of the unit.
Opening the hole to the left hand side of the
panel so that it can still be removed after piping
is in place. Holes can also be cut down through
the floor of the unit providing no cross-members
are cut out. Install air vent points to permit
complete air purging of the chilled water circuit.
Install drain valves in similar low points to
facilitate complete water system drainage. Install
temperature & pressure indicators in the water
piping at the unit to monitor water flow. Install
shut-off valves to isolate the unit from the piping
system during unit servicing. Note: Due to
possible high pressures resulting from rising
temperatures, do not close shut-off valves with
cold water in the evaporator.
It is important that the chilled water system be
cleaned before startup to avoid collecting debris
in the evaporator. After filling the system with
water (or a glycol solution), start pump, bleed off
trapped air, and check for proper flow rate by
measuring water pressure drop across evaporator.
NOTE: WATER QUALITY - ACXi
Evaporators used in these packages are made of
steel, copper and brass and are suitable for
operation with well-maintained water systems.
However, if the water used in evaporator is
corrosive, high in mineral content or entrained
solids, the water can cause reduced performance
and even failure of heat exchangers. Therefore, it
may be necessary to obtain the services of a
water treatment consultant and to provide and
maintain water treatment. This is particularly
important with glycol systems.
2.8 ELECTRICAL WIRING
In connecting power wiring to the unit, the
following precautions should be taken:
1.) All field wiring is to be in accordance with
the National Electric Code and must comply
with state and local codes. See Electrical
Data for minimum circuit ampacity and fuse
size.
- 10 -

2.0 INSTALLATION
FIGURE 2.5A ACXi 165-5SP-LN ISOLATOR LOCATION
Isolator Weights
Unit Model Dimensions - Inches
A Dim. B Dim. C Dim. D Dim. E Dim.
ACXi 165-5SP-LN 86 18 141 3/4 141 3/4 21
FIGURE 2.5B ACXI 165-5SP-LN ISOLATOR POINT LOAD DATA
Unit Model
Point Load - LBS
Total Operating
Pos. #1 Pos. #2 Pos. #3 Pos. #4 Pos. #5 Pos. #6 Weight (LBS)
ACXi 165-5SP-LN 2413 2666 2920 3039 2778 2517 16333
- 11 -

2.0 INSTALLATION
2.) Check unit wiring for damage and all
terminal connections for tightness. Unit
terminal blocks are to be connected with
copper conductors only, sized per ampacity
listed on unit data plate.
3.) Connections to unit should match the unit
nameplate in volts, phase, and Hertz. Voltage
must not vary beyond ±10% of nameplate
value and voltage imbalance between phases
must not exceed 2% at any time during
operation of the unit.
4.) Phase sequence to connectors L1, L2 and L3
shall be in that order. Check with Amprobe
phase sequence adapter PSA-1 or equivalent.
2.9 CONTROLS
2.9.1 CONNECTIONS
Controls which are to be field installed
should be connected in accordance with
the appropriate wiring diagram
accompanying the unit. The following
connections should be made where
applicable:
1.) Connect a set of normally open
auxiliary contacts from chilled water
pump contactor into unit controls as
shown on unit wiring diagram.
2.) Install a chilled water flow switch
(paddle type recommended) (or
differential pressure switch) in
straight length of chilled water piping
to avoid turbulence. Connect in same
electrical circuit as ( 1.)
2.9.2 SETTINGS
All controls are factory set, however
operating control settings are not always
applicable under all operating
conditions. For recommended control
settings, see wiring diagram
accompanying unit. Safety controls
must be set to factory
recommendations.
2.10 REQUEST FOR START-
UP REPRESENTATIVE
After the installation has been completed and
checked, Form 9180 must be filled out and sent
to the Dunham-Bush Service Department for
authorized start-up representative to perform the
initial start-up of the Dunham-Bush packaged
chiller. The purchaser will have competent
service and operating personnel in attendance to
assist in the work involved, and also to be trained
in the service and maintenance of this unit.
(During the warranty period, the manufacturer is
responsible for parts only upon proof of defective
workmanship or manufacture).
Following receipt of the signed Form 9180, a
representative will be sent to the customer. He
will inspect the installation to determine whether
it meets Dunham-Bush, Inc. requirements;
perform the initial start-up of the installation;
determine whether it is in satisfactory operating
condition; and instruct the specified customer
personnel in its operation and maintenance for
the length of time specified in the purchase
contract.
NOTE: Sump oil heaters should be energized
for a minimum of 24 hours and the oil
sump temperature must be at a
minimum of 100°F (38°C) prior to
arrival of start-up representative. This
will ensure that the oil is warm enough
to vaporize any dissolved refrigerant
and that the oil is within the normal
operating temperature range.
WARNING: The compressor (s) should be
started initially ONLY under the
direct supervision of an
Authorized Dunham-Bush, Inc.,
Start-Up Representative.
- 12 -

3.0 OPERATION
3.1 GENERAL
The unit should be started up only by a
refrigeration technician who is familiar with
accepted operation practices for refrigeration
systems.
Use small screw unit start-up report to record all
temperature, pressure, electrical readings and
control settings. A copy must be forwarded to
Dunham-Bush, Inc., before the warranty will be
honored.
3.2 UNIT PIPING
Each unit has a separate refrigerant circuit for
each compressor. See figure 3.2 for typical unit
piping schematic.
3.3 SYSTEM WATER FLOW
RATE
The quantity of chilled water being circulated
can be measured quite accurately (±5%) by
determining the water pressure drop through the
evaporator and reading GPM from the evaporator
pressure drop curve, Figure 3.3. Connect reliable
pressure gauges to valves installed in evaporator
entering and leaving water vent connections and
read pressure difference with chilled water pump
in operation. An alternative method of
determining GPM is to measure pressure
difference from pump inlet to outlet and read
GPM from pump curve.
3.4 STANDARD AMBIENT
UNIT OPERATION (65°F
MINIMUM AMBIENT)
INCLUDING OVERNIGHT
SHUT-DOWN AND
MORNING RESTART
Caution: These units may equipped with
manifold installed manual discharge valve that
must be opened before attempting to start.
Important: Do not use chilled water pump
operation via the flow switch or Aux. chilled
water pump contacts to start & stop this unit.
These are safety controls, not operational
controls.
3.4.1 AIR COOLED PACKAGE
CHILLER START-UP
The unit is ready for start-up when the
following procedures have been
completed.
1. Water piping for the evaporator is
installed and tested.
2. Electrical connections are made and
properly fused.
3. Unit has been leak tested. leaks
corrected, and charge completed.
4. Compressor crankcase heater(s) has
been energized for a minimum of 24
hours.
5. Calibrated refrigerant gages have been
connected to the suction and discharge.
6. Turn on the chilled water pump, check
direction of rotation and adjust the
water flow through the evaporator to
the specified flow rate. Bleed off all
entrained air.
7. Manually energize the fan starters and
check the fan rotation. Fans should
pull air through the condenser coil and
discharge vertically upwards.
8. Check all refrigerant valves to be sure
they are open.
9. Proceed to System Start-up.
Compressor #1 will start in about 15
minutes & proceed to load up if leaving
water temperature is above setpoint.
Compressor #2 will follows as the
demand dictates.
3.5 SYSTEM START UP
1. Before starting the compressor(s), check
all three phases of supply voltage, of all
legs of the motor. They must be within
±10% of the nameplate voltage. Check to
be sure compressor is not running
backwards.
- 13 -

3.0 OPERATION
FIGURE 3.2 ACXi 165-5SP-LN TYPICAL SCHEMATIC PIPING
- 14 -

1
10
100
100 1000
FLOW RATE - USGPM
PRESSURE DROP - FT WG .
3.0 OPERATION
FIGURE 3.3 EVAPORATOR WATER PRESSURE DROP
ACXi 165-5SP-LN
- 15 -

3.0 OPERATION
2. Start compressor(s), check the gages and note
if the pressures are within the prescribed
limits.
3. Check the refrigerant sight glass at the TX
Valve to be sure it is free of bubbles. If not,
charge as required to clean sight glass.
4. Stage unit down until all compressors are off
and check the compressor crankcase sight
glass for oil level. It should be 1/2 to 3/4 of
the compressor sight glass.
5. Restart the compressor. After an hour of
operation, the expansion valve superheat
setting should be checked, it should be
between 9° and 12°F at full load design
conditions. In some instances, it will be
necessary to lower the superheat setting to
ensure proper distribution. Turn the TX valve
adjustment stem clockwise to increase the
superheat setting and counterclockwise to
decrease the setting. Be sure and allow ample
time between each adjustment for the system
to rebalance.
6. The electrical control settings should be
checked and if necessary, reset to those
settings indicated on the wiring diagram.
Safety controls are factory set and must be
maintained at settings indicated on the wiring
diagram.
7. The temperatures of the chilled water both in
and out, should be checked to insure the unit
is operating within the desired temperatures.
3.6 SHUT-DOWN (OVERNIGHT
OR WEEKEND)
To shut-down in the unit with compressors on or
off, turn each individual compressor switch. Do
not close any valve. The chilled water pump may
then be turn off. If it is possible that the
overnight ambient will drop below 65°F, it is
preferable to leave the chilled water pump on.
Finally, do not open the main unit disconnect.
Main power is required to keep the sump heaters.
3.7 SEASONAL SHUT-DOWN
PROCEDURE
Standard Ambient Units
1. Follow standard overnight shut-down
procedure
2. Turn off chilled water pump
3. Close manual discharge valve
4. Close liquid valve on sealpot
5. If ambient temperature during the extended
shut-down period will not get below freezing,
the chilled water system may be left filled, If
the ambient temperature will be below
freezing, drain all water thoroughly, removing
all vent & drain plugs from both heads of the
evaporator, and blow out tubes will
compressed air to avoid serious stagnant
water corrosion.
6. Finally, it is recommended that an oil sample
be taken from each compressor & submitted
for lab analysis. Dunham-Bush offers this
service in its "Oil Kare" program. This
analysis should be done at the end of each
operating season or every 6 months if the unit
is used year round.
The power supply to the unit may be de-
energized to conserve energy. Just remember
that all heaters will now be inactive, and the
evaporator could freeze-up if not properly
drained.
3.8 SEASONAL START-UP
PROCEDURE
l. Check fan drives for wear, rust, propeller
clearance, etc. and make necessary repairs &
adjustments. Grease main fan shaft bearings
with a good grade of EP ball bearing grease.
2. Check & clean condenser fin surface if
necessary. Use a warm water soap solution,
being careful not to bend fins. Comb out bent
fin areas.
3. Check all power supply connections at all
points, and all control terminal screws for
tightness.
4. Energize main power to unit & leave on for at
least 24 hours in order for compressor to
thoroughly warm up.
5. Start chilled water pump and verify correct
flow-rate glycol % if required. Bleed-off
system air if necessary.
6. Open main discharge valve in discharge
header.
7. Open liquid valve on sealpot.
- 16 -

3.0 OPERATION
8. Turn control circuit power switch on, and all
individual compressor circuit switches. Press
computer keyboard reset key (RST).
Compressors should start after start-up clock
times out and will come on in sequence to
satisfy the existing load.
3.9 SAFETY RELIEF VALVES
Each pressure vessel is protected by a safety
relief valve as required by ASME Code. Each
compressor is protected by a relief valve which is
vented to atmosphere. Never install any kind of
shut-off valve in a safety relief vent line.
3.10 REFRIGERATION CYCLE
-MULTIPLE COMPRESSOR
ACXi
Following is the normal sequence of operation
for a unit installed in a typical air conditioning
system. Refer to Figure 3.2, the typical piping
schematic for multiple compressor ACXi unit.
Each vertical screw compressor discharges hot,
high pressure gas into a hot gas manifold and is
then split and routed into the left-hand and right-
hand side, condenser where it condenses,
rejecting heat to the outdoor air drawn through
the coil by fans. The liquid refrigerant from the
condenser is drain out from bottom of the
condenser coil through liquid stop valve into a
liquid subcooler.
The refrigerant flows through the liquid
subcooler, dropping its temperature causing it to
flash. Liquid is cooled from the liquid subcooler,
drains to liquid line filters drier and sight glass,
liquid solenoid before through DX evaporator
main expansion valve which is at an intermediate
pressure between condenser and evaporator.
Refrigerant flows into the DX evaporator, where
it boils, cooling the water flowing outside
evaporator tubes. Vapor from the boiling
refrigerant flows up the suction pipes through
shut-off valves, suction check valves and suction
filters (inside compressor) into compressors
where it is compressed and starts the cycle again.
Vapor flows from the top of the liquid subcooler
into the compressors at the vapor injection ports,
which feed it into the compressors part way
through the compression process. Check valve
will prevent backflow at shutdown.
3.11 FAN CYCLING
On start-up, all fan will remain off (some units
may have base fans which run together with
compressor). As the head pressure builds up,
next fan stage will start. Subsequently fan stage
will start if the head pressure continues to rise.
Refer wiring circuit diagram for number of fan
stage.
3.12 LIQUID INJECTION
Each compressor is fitted with a liquid
injection system designed to feed refrigerant
liquid into the compressor to provide
additional motor cooling as required. The
liquid injection control TXV will modulate to
hold the compressor discharge gas temperature
below 170ºF, the maximum discharge
operating temperature of these compressors.
3.13 HYDRAULIC CAPACITY
CONTROL SYSTEM
Each compressor has a hydraulic control system
to supply the proper force necessary to actuate
the capacity control slide valve, thereby
regulating compressor loading for maximum unit
capacity. It is composed of a normally closed
solenoid valve (A), a normally open solenoid
valve (B), an internal pressure regulating valve.
With valves A and B both energized (A open, B
closed) during normal compressor operation,
high pressure oil is directed to the slide valve.
This pressure acts on the surface of the slide
valve piston creating a force which is sufficient
to overcome the opposing spring force and to
move the valve in the direction of increasing
capacity.
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NORMALLY
OPEN
UNLOADING
SOLENOID
SUCTION
SOLENOID
LOADING
NORMALLY
CLOSED
SCHRADERVALVE
CHECK
SERVICE
SUCTION
VALVE
'B'
'A'
VALVE
BOX
TERMINAL
3.0 OPERATION
When the compressor is given a "hold"
command, valve A is de-energized (closed) and
slide valve movement is halted. The internal
pressure regulating valve allows oil to bleed from
the slide valve chamber during the hold
condition. If valve B is then de-energized (open),
the high pressure oil acting on the slide valve
will be vented to suction, and the pressure in the
slide valve chamber will be reduced. The slide
valve spring will now move the slide valve back
toward the minimum capacity position.
Under standard conditions, the compressor will
load in 60 seconds and unload in 55 seconds.
SLIDE VALVE POSITION
UNLOADING LOADING HOLD
SOLENOID VALVE A
(NORMALLY CLOSED) CLOSED (DE-ENERGIZED) OPEN (ENERGIZED) CLOSED (DE-ENERGIZED)
SOLENOID VALVE B
(NORMALLY OPENED) OPEN (DE-ENERGIZED) CLOSED (ENERGIZED) CLOSED (ENERGIZED)
FIGURE 3.13 COMPRESSOR CAPACITY CONTROL DETAIL
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4.0 ELECTRICAL
4.1 ELECTRICAL DATA
ACXI Unit Data Compressor Fan Motors
Model
ACXi
Electrical
Spec.
V- PH- Hz
Min Circuit
Ampacity
(A)
Max
Branch
Fuse Size
(A)
Qty. Model RLA
Each
(A)
LRA
Each
(A)
Qty. Hp
Each
(A)
FLA
Each
(A)
165-5SP-
LN
400 - 3- 50 440A 600A 1
1MSC 1210 MSC 1212 163 202 995 1050 12 0.5 2.0
4.2 WIRING DIAGRAM
Figure 4.2 are typical wiring diagrams for a 2
compressor unit. This may not be an accurate
representation of your unit. It is best to use the
wiring diagram mounted in the package control
panel. A copy of that diagram is furnished with
the unit owner’s manual.
4.3 TYPICAL OPERATION
In order to start a compressor, the following
conditions must be met:
-Phase Control Relay (PCR) setting
-Chilled water pump running
-Chilled water flow switch made
-Compressor circuit breakers on
-Customer unit control contact closed
-Control switch and compressor switches on
-Reset pressed on microcomputer keypad
-Power has been on the microcomputer for 15
minutes
-All safety conditions satisfied
-Leaving chilled water temperature 2°F or more
above setpoint
A compressor is started by first energizing 1M1
followed by 1M2. Anti-recycle time of 15
minutes is initiated within the computer at start.
When the compressor starts, the microcomputer
monitors amperage by means of 1CT, voltage
using 3T, leaving water temperature using TS,
and condensing pressure. These inputs are used
to control the loading and staging of the
compressor. The compressor's loading is
controlled by pulsing signals to the load and
unload solenoids.
If the safety conditions are satisfied for the #2
compressor, at least 1 minute has elapsed since
starting #1 compressor, and leaving water
temperature remains above the deadband; 2M1
and 2M2 will be activated by the micro-
computer, #2 compressor also has a 15 minute
antirecycle timer built into the microcomputer.
Loading of the #2 compressor is controlled the
same as compressor #1.
To shut down the unit automatically, the
customer control contacts must be opened. To
shut down the unit manually, simply shut off the
compressor switches. This will cause a no-run
alarm that must be reset to restart the
compressor.
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CHECKEDREV. NO. DATE APPROV.
4.0 ELECTRICAL
FIGURE 4.2 ACXi 165-5SP-LN WIRING SCHEMATIC
- 20 -