AAON RM Series Service manual

1
RM SERIES
HEATING • COOLING & COMBINATION
ROOFTOP UNITS
INSTALLATION
INSTRUCTION
MANUAL
▲
! WARNING
If the information in this manual is not followed
exactly, a fire or explosion may result causing
propertydamage,personalinjuryorlossoflife.
FOR YOUR SAFETY
DO NOT STORE OR USE GASOLINE OR OTHER
FLAMMABLE VAPORS AND LIQUIDS IN THE
VICINITY OF THIS OR ANY OTHER APPLIANCE.
• EXTINGUISH ANY OPEN FLAME.
• DO NOT TOUCH ANY ELECTRICAL SWITCH.
• DO NOT TRY TO LIGHT ANY APPLIANCE.
• DO NOT USE ANY PHONE IN YOUR BUILDING.
• IMMEDIATELY CALL YOUR GAS SUPPLIER FROM A
NEIGHBOR'S PHONE.
FOLLOW THE GAS SUPPLIER'S INSTRUCTIONS.
• IF YOU CANNOT REACH YOUR GAS SUPPLIER,
CALL THE FIRE DEPARTMENT.
FOR YOUR SAFETY
WHAT TO DO IF YOU SMELL GAS
7-2003
AAON
®

2
SECTION PAGE NUMBER
GENERAL DESCRIPTION …………………………………………………………………………… 03
Unpacking
Certification
Codes and Ordinances
OWNER'S INFORMATION …………………………………………………………………………… 04
HEATING / COOLING SYSTEMS …………………………………………………………………… 05
INSTALLATION ………………………………………………………………………………………… 06
Setting the Curb / Unit ………………………………………………………………………… 07
Service Clearances
Outside Air Hood………………………………………………………………………………… 08
Electrical
Gas Piping………………………………………………………………………………………… 09
Condensate Piping ……………………………………………………………………………… 10
GAS UNIT LIGHTING INSTRUCTIONS …………………………………………………………… 11
PERIODIC INSPECTION PROCEDURES ………………………………………………………… 12
Gas Heating, Cooling, Electric, Steam, Hot Water & Chilled Water Units
SERVICE, TROUBLE SHOOTING & MAINTENANCE ………………………………………… 14
Lubrication
Cleaning
FILTER INSTALLATION / REPLACEMENT ……………………………………………………… 15
SERVICING ……………………………………………………………………………………………… 16
Rooftop Unit Replacement Parts …………………………………………………………… 18
SEQUENCE OF OPERATIONS ……………………………………………………………………… 19
Heating
Cooling
Optional Economizer
VAV Systems …………………………………………………………………………………… 20
Power Exhaust Options
COMPRESSOR CHECKOUT PROCEDURE ……………………………………………………… 21
IGNITION CONTROL CHECKOUT PROCEDURE ……………………………………………… 22
FACTORY START-UP FORM ………………………………………………………………………… 23
Owner should pay particular attention to the words: NOTE, CAUTION AND WARNING.
NOTES are intended to clarify or make the installation easier. CAUTIONS are given to prevent
equipment damage. WARNINGS are given to alert owner that personal injury and/or equipment
damage may result if installation procedure is not handled properly.
TABLE OF CONTENTS
AAON
®
It is the intent of AAON, Inc. to provide accurate and current specification information. However, in the interest of product improvement,
AAON, Inc. reserves the right to change pricing, specifications and/or design of it's products without notice, obligation or liablity.
© 2003
AAON, Inc. , all rights reserved throughout the world.
AAON & AAONAIRE are registered trademarks of AAON, Inc. , Tulsa, OK.
R15690 (7-03)

3
GENERAL DESCRIPTION
CERTIFICATION
• GAS HEAT MODELS
(a) Design Certified as a forced air furnace with or without cooling unit.
(b) Certified for outdoor installation only.
(c) Certified for installation on combustible roof with a minimum of 12" high curb.
(d) Certified with heat exchanger located downstream from evaporator coil.
• STEAM OR HOT WATER HEAT MODELS
(a) Certified as a forced air furnace with or without cooling unit.
(b) Certified for outdoor installation only.
(c) Certified for installation on combustible roof with a minimum of 12" high curb.
(d) ARI certified hot water coils.
• ELECTRIC HEAT MODELS
(a) Certified as an electric warm air furnace with or without cooling unit.
(b) Certified for outdoor installation only.
(c) Certified for installation on combustible roof with a minimum of 12" high curb.
• COOLING MODELS
(a) Certifiedasa commercial centralair-conditioner with orwithout electrically operatedcompressor.
(b) Certified for outdoor installation only.
(c) Certified for installation on combustible roof with a minimum of 12" high curb.
(d) ARI certified coils.
Theunitsaredesignedasself-containedheating,cooling
orcombinationunitsforoutdoor installation only,using
therefrigerant shown onthe rating plate,chilledwater,
naturalor propanegas, electricresistance, steamor hot
water.
UNPACKING
When received, the unit should be checked for damage
that might have occurred in transit. If damage is found,
itshouldbenotedonthecarrier'sFreightBill.Arequest
for inspection by carrier's agent should be made in
writing at once.
CODES AND ORDINANCES
System should be sized in accordance with National
Warm Air Heating and Air Conditioning Association
Literature,ortheGuideofAmericanSocietyofHeating,
Refrigeration and Air Conditioning Engineers. The
installationmustconformwithlocalbuildingcodesor,in
the absence of local codes with (United States) National
Fuel Gas Code "ANSI-Z223.1", (Canada) current CAN /
CGA- B149.1 or . 2. Installation Codes for Gas Burning
Appliances and Equipment, current C.S.A. Standard
C22.1, Canadian Electrical Code Part 1, and C.S.A.
StandardB52MechanicalRefrigerationCode,andLocal
Plumbing or Waste Water Codes.
▲
! WARNING
Improper installation, adjustment, alteration,
service or maintenance can cause property
damage, personal injury or loss of life.
Installation and service must be performed
by a qualified installer, service agency
or the gas supplier.
NOTE: These units must not be used as a
"construction heater" at any time during any phase
of construction. Very low return air temperatures,
harmful vapors, and misplacement of the filters
will damage the unit and its efficiency.
▲
The Clean Air Act of 1990 bans the
intentional venting of refrigerant (CFC's and
HCFC's) as of July 1, 1992. Approved
methods of recovery, recycling or reclaiming
must be followed. Fines and/or incarceration
may be levied for non-compliance.
!IMPORTANT

4
OWNER'S INFORMATION
WARNING
Failure to observe the following instructions will result
in premature failure of your system, and possible void-
ing of the warranty.
DIRECT EXPANSION (DX) COOLING UNITS
Never cut off the main power supply to the unit, except
for complete shutdown. When power is cut off from the
unit, compressors with crankcase heaters cannot pre-
vent refrigerant migration. The compressor will cool
down, and liquid refrigerant will accumulate in the
compressor. The compressor is designed to pump only
refrigerant gas and damage may occur when power is
restored.
If power must be cut off for more than an hour, turn the
thermostatsystemswitchto"OFF",andleaveitoffuntil
the main power switch has been turned on again for at
leasttwentyfourhoursonunitswith compressor crank-
caseheaters. Thiswillgivethecrankcaseheatertimeto
clearliquidaccumulationoutofthecompressorbeforeit
is required to run.
Always control the system from the thermostat, or con-
trol panel, never at the main power supply (except in an
emergency or complete shutdown of the system).
During the cooling season, if the air flow is reduced due
to dirty air filters or other reasons, the cooling coils will
get too cold and result in excessive liquid return to the
compressor. As the liquid concentration accumulates,
oiliswashedoutofthecompressor,leavingitstarvedfor
lubrication.
The compressors must be on a minimum of 4 minutes
andoffforaminimumof5minutes. Thecycleratemust
not exceed 8 starts per hour.
THE COMPRESSOR LIFE WILL BE SERIOUSLY
SHORTENEDBYRESULTINGREDUCEDLUBRICA-
TION, AND THE PUMPING OF EXCESS AMOUNTS
OF LIQUID OIL AND REFRIGERANT.
GAS OR ELECTRIC HEATING
Thesystemisdesignedtoheatagivenamountofaireach
minuteitoperates. Iftheamountofairheatedisgreatly
reduced (approximately 1/3 capacity), the heat ex-
changer / heater coil temperature will increase above
acceptable level and result in shut down by a high
temperature safety switch incorporated either in the
heat exchanger or the heater area.
GASHEATUNITS-WARNING: If,duetosafetyswitch
shutofforgassupplyshutofffailure; ALWAYSCLOSE
MANUAL GAS VALVE TO UNIT PRIOR TO ANY
ELECTRICAL SERVICE.
PROLONGED OVERHEATING OF THE HEAT
EXCHANGER WILL SHORTEN ITS LIFE.
WARNING: Improper installation, adjustment, alter-
ation, service, or maintenance can cause property dam-
age, personal injury or loss of life. Installation and
service must be performed by a qualified installer, ser-
vice agency or if gas fired units, the gas supplier. Refer
to installation instructions provided with the unit and
this manual.
CAUTION: While the following incorrect operations
may not cause damage to the system, they will impair
the performance, and may cause the built-in safety
devices to cut the system off completely.
1. LOW AMBIENT OPERATION
The cooling section of a direct expansion (DX) unit
willnotoperateproperlywhentheoutdoortempera-
ture is below 55°F. Outside air intake options are
necessary if operation below 55°F is expected.
2. MULTIPLE UNIT OPERATION
When several units are used in conditioning the
space, and any are combination heating-cooling
units,allsystem thermostat switches mustbesetat
either heating, cooling, or set at "off". Do not run
part of a system switched to an opposite mode.
Cooling only units should be switched to "off" at the
thermostat during the heating season.
WIRING DIAGRAMS
A complete set of unit specific wiring diagrams in both
ladder and point-to-point form are laminated in plastic
and located inside the control compartment door.
CONDENSATE PIPING
A drain trap is to be connected to the drainpan. If codes
require a condensate drain line, it should be the same
pipesizeasthedrainnippleandshouldpitchdownward
toward drain.
The condensate drain pipe ("P" trap) is factory supplied
and shipped in the control access compartment for field
installation. Anairbreakshould beusedwithlongruns
of condensate lines.
▲
! WARNING
Scroll compressors will be damaged by
operation with the wrong rotation.
THE LOW PRESSURE SWITCH HAS BEEN
DISCONNECTED AFTER TESTING
AT THE FACTORY.
The wiring must be reconnected and proper
rotation determined at the time of start-up by
a qualified service technician using suction
and discharge pressures gauges.
Any alteration should only be made at
the unit power connection.

5
GAS HEATING SYSTEM
The heating section is for use with natural gas supply
pressureof 6"to10.5"WaterColumn. Theunitmayalso
utilize propane gas with a supply pressure to the valve
of 11" to 12" Water Column. The rating plate on the
furnace must be inspected to make sure the unit is
stamped for proper gas. A 1/8" pressure tap should be
fieldsupplied by theinstaller in thepiping just aheadof
the gas valve. The pressure tap on the outlet end of the
gas valve can be checked to verify manifold pressure of
3.2" to 3.5" for natural gas.
Combustion air is supplied by a centrifugal blower
whichdrawsin outside airthroughaprotected opening.
This induced draft blower introduces the air to the
burnertubeswhichassuresevenprimaryandsecondary
air flow.
All heating system and related safety controls are 100%
tested on each unit prior to shipment.
INSTALLATION IS TO BE ADJUSTED
TO OBTAIN AN AIR TEMPERATURE RISE
WITHIN THE RANGE SPECIFIED ON THE
RATING PLATE.
The units are equipped with a direct spark ignition
system which proves the burner operation during each
call for heat. Power to the ignition control is 24 Vac to
reduce hazards. Burner ignition is by a high intensity
spark.
Whenheat iscalledfor, thecooling system isinoperable
except for the indoor blower motor. Heating is accom-
plished by firing gas into the heat exchanger assembly.
ELECTRIC HEATING SYSTEM
Heating is accomplished by passing electrical current
through a specified amount of resistance heaters which
produce the required heat. The indoor blower motor
energizes at the same time as the heaters.
STEAM OR HOT WATER HEATING SYSTEM
Heating is accomplished by passing steam or hot water
through the steam or hot water coil assembly.
COOLING SECTION • DX
All direct expansion refrigeration systems are factory
assembled, charged with refrigerant, tested and oper-
ated. Onallunits8tonandlargertherefrigerantsystem
includesmultiplecircuitevaporatorandcondensercoils
providing two or more stages of cooling. These systems
include liquid line filter driers, expansion valves and
fully hermetic compressors. Compressors are equipped
with a positive pressure forced lubrication system. The
air cooled condenser coil(s) are constructed of copper
tubesandmechanicallybondedaluminumfinsandairis
pulled through by propeller fans. The evaporator coil is
draw through type constructed of copper tubes and
mechanically bonded aluminum fins.
The refrigeration section of these appliances has been
found acceptable with applicable provisions of "ANSI /
UL1995"andcurrent"C.S.A.StandardC22.2" byE.T.L.
NOTE: Crankcase Heater Operation
Some units are equipped with a compressor crankcase
heater,whichshouldbeenergizedatleast24hoursprior
to setting the thermostat for cooling operation.
COOLING SECTION • CHILLED WATER
or NON-COMPRESSORIZED UNIT
Chilled water or non-compressorized units have factory
installed coils. Systems are provided with internal
header connections for field piping.
Coils are constructed of copper tubes and mechanically
bonded aluminum fins.
HEATING & COOLING SYSTEMS
NORMAL OPERATION
HEATING
Set the thermostat system switch to "HEAT".
Set the thermostat fan switch to "AUTO" or "ON".
Set the thermostat temperature at the desired point.
COOLING
Set the thermostat system switch to "COOL".
Set the thermostat fan switch to "AUTO" or "ON".
Set the thermostat temperature at the desired point.
AIR CIRCULATION
Set the thermostat system switch to "OFF".
Set the thermostat fan switch to "ON".
Do not change temperature setting.
With these settings, the air circulating blower will run
continuously but the air will not be heated or cooled.
SYSTEM OFF
Set the thermostat system switch to "OFF".
Set the thermostat fan switch to "AUTO".
Do not change temperature setting.
With these settings, the system is shut down, with the
exception of the control system power (24 Vac), and the
crankcase heater of the compressor (approx. 60W).
DO NOT TURN OFF THE MAIN POWER SWITCH.
NIGHT AND VACANT WEEKEND OPERATION
To reduce the operation time during low load periods,
it is recommended that the temperature setting be
increasedfivedegreesduringtheseperiodsofthecooling
season, and decreased ten degrees during the heating
season.

6
ROOF
DECK *
STRUCTURAL
STEEL *
DUCT /
FLEX
CONNECTOR*
GASKET
COUNTER
FLASHING *
RIGID
INSULATION *
CURB
WOOD
NAILER * CANT STRIP *
ROOFING
MATERIAL*
DUCT RAIL
DETAIL 'A'
OPEN BOTTOM CURB
DUCT RAIL CONNECTION
* FIELD SUPPLIED
▲
! CAUTION
If outside air is in contact with the bottom
of the unit, the unit must have the bottom
insulation option or be field insulated.
DO NOT DRILL OR PUNCH HOLES IN BASE
OF UNIT FROM INSIDE THE UNIT OR FROM
BELOW TO ATTACH DUCTWORK. LEAKING
MAY OCCUR IF UNIT BASE IS PUNCTURED.
INSTALLATION
DETAIL 'A'
ACOUSTIC CURB
* FIELD SUPPLIED
WOOD
NAILER *
GASKET
ROOF
DECK *
ROOFING
MATERIAL*
COUNTER
FLASHING *
STRUCTURAL
STEEL *
RIGID
INSULATION *
CANT STRIP *
SOLIDBOTTOM
ACOUSTIC CURB
DUCT / FLEX CONNECTOR*
12
12
12
12
12
12
12
12
12
12
12
12
12
12
▲
! WARNING
INSULATION MATERIALS MAY
BE COMBUSTIBLE
WOOD
NAILER *
DETAIL 'A'
DUCT / UNIT CONNECTION
* FIELD SUPPLIED
COUNTER
FLASHING *
RIGID
INSULATION *
CURB
ROOFING
MATERIAL*
CANT STRIP *
ROOF
DECK *
STRUCTURAL
STEEL *
GASKET
DUCT /
FLEX
CONNECTOR*
SECTIONAL VIEW OF UNIT ON ROOF CURB
SEE DETAIL "A"

7
INSTALLATION continued
AAONRooftopunitsaredesignedforfast,easyinstalla-
tion. The curb is mounted first and must be located so
duct connections will clear any structural members of
the building.
SETTING THE CURB
When using the factory curb, make openings in roof
decking large enough to allow for duct penetrations and
workspace only. Do not make openings larger than
necessary. Set the curb to coincide with the openings.
CURB MUST BE LEVEL.
SETTING THE UNIT
Ifcablesorchainsareusedto hoist the unittheymustbe
the same length and care should be taken to prevent
damage to the cabinet / coils or condenser fans.
Itisrecommendedtheunitbehoistedwiththeoutsideair
hood in the shipped position. However the unit may be
hoisted with the outside air hood in an open position.
Before lifting unit, be sure that all shipping material is
removedfromunit. Secure hooksandcablesatalllifting
points / lugs provided on the unit.
Prior to setting the unit onto the roof curb, be sure that
the gasket material has been applied to curb on all
surfaces meeting with the unit.
Hoist unit to a point directly above the curb and duct
openings. Carefullylowerandalignthe unit with utility
and duct openings unit perimeter fits around the curb.
Make sure the unit is properly seated on the curb and is
level.
Gas fired units should be installed so that the flue
dischargeventislocatedaminimum120"awayfromany
opening through which combustion products might en-
ter the building. Unit location must assure combustion
and ventilation air flows are never obstructed.
Neverpointfluedischargeindirectionoffreshairintake
for other equipment.
Improper installation, adjustment,
alteration, service or maintenance can
cause property damage, personal injury
or loss of life. Installation and service must
be performed by a qualified installer,
service agency or the gas supplier.
Install the gas fired unit to assure the flow
of combustion and ventilating air is not
obstructed from reaching the heater and
that the flue outlet is located at least
120 inches away from any opening
through which combustion products
could enter the building.
▲
! WARNING
▲
! IMPORTANT
PRIOR TO SETTING THE UNIT ON THE CURB.
To insure proper isolation and seal
between the unit & curb, gasket material
MUST BE APPLIED to the curb on
ALL SURFACES meeting with the unit.
Where the supply or warm air duct passes
through a combustible roof, a clearance
of one inch must be maintained between
the outside edges of the duct and
combustible material in accordance
with National Fire Protection Association
Standard No. 90A. Provide flashings or
enclosure between structure and roof
and all joints must be sealed with mastic
roofing to ensure a watertight seal.
All roofing work should be performed
by qualified roofing contractors.
▲
! CAUTION
Back - Return Air End
LOCATION UNIT SIZE
2 - 7
SERVICE CLEARANCES
48"
Front - Control Door Side 48"
Left Side 6"
Right Side - Access Doors 60"
Top UNOBSTRUCTED
8 - 15 16 - 30
48"
48"
6"
60"
48"
48"
6"
60"
LIFTING DETAIL
TYPICAL FOR
2 - 30 TON UNITS
99" minimum
length

8
ELECTRICAL
Verify the unit data plate voltage agrees with the power
supply. Route power and control wiring through the
utility entry. Do not run power and signal wires in the
same conduit. Connect power according to the (unit
specific) wiring diagram provided.
Protect the branch circuit in accordance with code re-
quirements. Control wires should not be run inside the
sameconduit. Theunitmustbeelectricallygroundedin
accordance with the current National Electric Code,
ANSI / NFPA No. 70. In Canada use current C.S.A.
Standard C22.1 Canadian Electric Code Part 1.
Power wiring is to the unit terminal block or main
disconnect. All wiring beyond this point has been done
bythemanufacturerandcannotnotbemodifiedwithout
effecting the unit's agency / safety certification.
INSTALLATION continued
OUTSIDE AIR HOOD
CAUTION: Prior to unit operation, the outside air hood
must be opened as shown below:
AIRFLOW IS TO BE ADJUSTED AFTER
INSTALLATION TO OBTAIN AN AIR
TEMPERATURE RISE WITHIN THE RANGE
SPECIFIED ON THE RATING PLATE.
DUE TO JOB SPECIFICATION REVISIONS,
IT MAY BE NECESSARY TO ADJUST OR
CHANGE THE SHEAVE OR PULLEY TO
OBTAIN THE DESIRED AIRFLOW
AT THE TIME OF INSTALLATION.
Removeshippingscrewsfromeachsideofthehoodinthe
"closed" postion. Lift hood to the "open" position, seal
flange and secure with sheet metal screws.
Air hoods may vary according to unit size and options.
The illustration shown is for practical guidelines for all
outside air hoods.
Outdoor air intake adjustments should be made accord-
ing building ventilation or local code requirements.
NOTE: All units are factory
wired for 208 / 230, 460 or
575 volt. If unit is to be
connected to a 208v supply,
the transformer must be
rewired for 208v service.
For 208v service interchange
the yellow and red conductor
on the low voltage control
transformer.
RED - BLK 208 volt ;
YEL - BLK 230 volt.
▲
!CAUTION
START-UP TECHNICIAN MUST CHECK BLOWER
MOTOR AMPERAGE TO ENSURE THAT THE
AMPERAGE LISTED ON THE MOTOR NAMEPLATE
IS NOT EXCEEDED.
▲
On three phase units the rototation must be
checked on ALL MOTORS AND COMPRESSORS.
SCROLL COMPRESSORS ARE DIRECTIONAL.
Rotation must be checked on start-up by a
qualified service technician using
suction and discharge gauges.
Scroll compressors will FAIL if run in the wrong
direction. Blower and condenser rotation
should be checked and only be altered if
necessary at the power connection.
!CAUTION
▲
!WARNING
Electric shock hazard. Can cause injury or death.
Before attempting to perform any service or
maintenance, turn the electrical power to unit to
OFF at disconnect switch(es).
Unit may have multiple power supplies.
APPLY
SILICONE CAULKING
ON TOP &
BOTH SIDES
OF AIR HOOD
AIR HOOD SHOWN IN THE OPEN POSITION

9
GAS PIPING
Size gas piping to supply the unit with 6" to 10.5" water
column pressure for natural gas or 11" water column
pressure for propane when all gas consuming devices in
the building connected to the same gas system are
operating. Installpipinginaccordance with localcodes,
the piping must conform with the latest ANSI-Z223.1
National Fuel Gas Code; in Canada, Current Standard
CAN / CGA-B149, Installation Codes for Gas Burning
Appliances and Equipment.
Some utility companies will require pipe sizes larger
than the minimum sizes listed.
NOTE: Local Codes may require the use of a manual
maingasshut-offvalveandunion,(furnished by others)
installed in the gas line external to the unit.
GAS PIPING is to be supported DIRECTLY AT CON-
NECTION TO UNIT and must not be strained or bent
and shall be supported by metal straps, blocks or hooks
at intervals not to exceed that shown in the following
table:
Pipejoint compounds usedonall gas pipingconnections
shall be resistant to the action of petroleum gases.
An1/8"NPTpluggedtapisrequiredimmediatelyahead
of the unit gas control valve.
All piping connections shall be checked with a soap
solution for gas leaks before operating the appliance.
INSTALLATION continued
SIZE OF PIPE INTERVALS (feet)
GAS PIPING SUPPORT
1/2" 6'
3/4" or 1" 8'
1 1/4" or larger (horizontal) 10'
1 1/4" or larger (vertical) every floor level
Nominal
Iron Pipe
Size, Inches 10 50 100 200
GAS PIPING CAPACITIES
3/4" 278 115 79 55
1" 520 215 150 100
1 1/4" 1050 440 305 210
1 1/2" 1600 670 460 320
2 3050 1270 870 610
2 1/2" 4800 2000 1400 980
LENGTH OF PIPE, FEET
Max. Capacity of Gas Pipe in Cubic Ft. Per Hour*
*At gas pressure of 0.5 PSIG or less and a pressure
drop of 0.5 inches of water. Specific gravity = 0.60.
UNIT SIZE / TONS INPUT / MBH
GAS PIPING SIZES
02 - 03 69 3/4"
04 90 3/4"
05 - 06 - 07 90 - 180 3/4"
08 - 10 180 - 270 - 351 3/4"
13 - 15 180 - 270 - 390 3/4"
16 - 30 270 - 390 - 480 3/4"
PIPE SIZE
Gaspiping informationisfor practicalguidelines and is
typical for one gas valve. For units with dual heat
exchangers, duplicate gas piping to number two gas
valve.
GAS PRESSURE REGULATOR & OVER-PRESSURE
PROTECTION DEVICE
On applications where gas service to the unit is greater
than 10.5"w.c. and less than 2-psi, a gas pressure regu-
lator must be installed.
At supply pressures in excess of 2-psi and less than 5-
psi, ANSI Z21.80 line regulator standard requires a
means (an over-pressure protection device / OPD) to
limitthedownstreampressureto2-psimaximum,inthe
event of regulator failure.
In compliance with the ANSI Standard, installations
exceeding 2-psi and less than 5-psi nominal require a
tested and approved over-pressure protection device for
use with the regulator.
For proper heater operation, pressure to the regulator
MUST NOT BE greater than 5-psi.
Utility
Access
Gas
Shut-off
Valve*
Heat
Exchanger
Gas
Valve
Union*
GAS PIPING ILLUSTRATION
*Gas piping field installed by others
Optional
Gas Pressure Regulator

10
INSTALLATION continued
CONDENSATE PIPING
AAONunitsareequipped withdrainconnectionsand'P'
traps are furnished with the equipment. All drain
connections must be used and individually trapped to
ensure a minimum amount of condensate accumulation
in the drain pans.
Drainage of condensate directly onto the roof may be
acceptable in certain areas, refer to applicable codes. If
condensateisto draindirectlyontotheroof,asmalldrip
pad should be placed below the drain to protect the roof
from possible damage.
When condensate is piped into the building drainage
system, the drain pipe must penetrate the roof external
to the unit itself. The drain line should be pitched away
from the unit at least 1/8" per foot. On longer runs, an
air break should be used to ensure proper drainage.
Drainpansinairconditioningequipmenthavemoisture
presentandrequireperiodiccleaningtoremovebuildup
of algae and/or bacteria. Cleaning of the drain pans
reduceprobabilityofpluggeddrainlinesandoverflowof
the pan itself. All cleaning of the drain pans and inside
of the equipment should be done by qualified personnel.
Thefurnacemustbeisolatedbyclosingthemanualshut
off valve or disconnected from the gas supply piping
during pressure testing of the piping system with pres-
sures in excess of 1/2 PSIG.
The flow of combustion and ventilating air shall not be
blocked or otherwise obstructed in any way.
After electrical power is turned on, set unit controls for
heating, and check for operation.
When checking burner operation, flames should be ob-
served as blue with slight or no yellow tipping. There
should be no sign of flames floating or lifting off or away
from the main burners.
NOTE: Incaseemergencyshutdownisrequired,turn
off the main manual gas shut-off valve and disconnect
main electrical power to unit. These devices should be
properly labeled by the installer.
IMPORTANT NOTICE:
All gas-fired heat exchangers are completely tested at
thefactorybefore shipment. This willremovenearlyall
of the oils that have been used in the manufacturing
process, however, trace amounts may remain. When
performingthe initialstart-up at the jobsite, itis highly
recommended that people or any other living animals,
thatmaybesensitivetotheresidualodorsorgases,NOT
be present in the conditioned space during the start-up.
In all cases, including the initial factory firing and
testing, all of the gases will be under the minimum
acceptable level of concentration for human occupancy.
DO NOT USE OPEN FLAME OR OTHER SOURCE
OF IGNITION FOR LEAK TESTING.
When pressure testing the gas supply piping, the
furnace must be isolated or disconnected by
closing the individual manual shut-off valve from
the gas supply. Gas valves can be damaged if
subjected to more than 0.5 psig pressure.
! WARNING
Some soaps used for leak detection are
corrosive to certain metals. Carefully
rinse piping thoroughly after leak
test has been completed.
! CAUTION
Those sensitive to odors or gases from
trace amounts of residual oils
should NOT be present in the
conditioned space during the start-up
of a gas-fired installation.
! WARNING
Typical 'P' trap
connection
FOR PROPER UNIT OPERATION,
DRAIN TRAP MUST BE INSTALLED AS SHOWN.
USE ABS TYPE CEMENT TO JOIN THE CONNECTIONS.

11
GAS UNIT LIGHTING INSTRUCTIONS
WARNING: IF YOU DO NOT FOLLOW THESE INSTRUCTIONS EXACTLY, A FIRE OR EXPLOSION MAY
RESULT CAUSING PROPERTY DAMAGE, PERSONAL INJURY OR LOSS OF LIFE.
A. This appliance does not have a pilot. It is equipped with an
ignition device which automatically lights the burner.
Do not try to light the pilot by hand.
B. BEFORE OPERATING smell all around the appliance area
for gas. Be sure to smell next to the floor because some gas
is heavier than air and will settle on the floor.
WHAT TO DO IF YOU SMELL GAS
• Do not try to light any appliance.
• Do not touch any electric switch; do not use any phone
in your building.
• Immediately call your gas supplier from a neighbor's phone.
Follow the gas supplier's instructions.
• If you cannot reach your gas supplier, call the fire department.
C. Use only your hand to push in or turn the gas control knob.
Never use tools. If the knob will not push in or turn by hand,
don't try to repair it, call a qualified service technician. Force
or attempted repair may result in a fire or explosion.
D. Do not use this appliance if any part has been under water.
Immediately call a qualified service technician to inspect the
appliance and to replace any part of the control system and
any gas control which has been under water.
OPERATING INSTRUCTIONS
5. Open control access panel.
6. Push in gas control knob slightly and turn clockwise to "OFF".
NOTE: Knob cannot be turned to "OFF" unless knob is pushed
in slightly. Do not force.
7. WAIT five (5) minutes to clear out any gas. Then smell for gas, including
near the floor. If you smell gas, STOP! Follow "B" in the safety
information above on this label. If you don't smell gas, go to the next step.
8. Turn gas control knob counterclockwise to "ON".
9. Close control access panel.
10. Turn on all electric power to the appliance.
11. Set thermostat to desired setting.
12. If the appliance will not operate, follow the instructions
"To Turn Off Gas To Appliance" and call your service
technician or gas supplier.
1. STOP! Read the safety information above this label.
2. Set the thermostat to lowest setting.
3. Turn off all electric power to the appliance.
4. This appliance is equipped with an ignition device which
automatically lights the burner. Do not try to light the pilot by
hand.
1. Set the thermostat to lowest setting.
2. Turn off all electric power to the appliance if service
is to be performed.
3. Open control access panel.
4. Push in gas control knob slightly and turn clockwise to
"OFF". Do not force.
5. Close control access panel.
ON
OFF
GAS INLET
TO TURN OFF GAS TO APPLIANCE
GAS CONTROL KNOB
SHOWN IN "ON"
POSITION
FOR YOUR SAFETY READ BEFORE OPERATING

12
PERIODIC INSPECTION PROCEDURES
GAS HEATING UNITS
1. The flow of combustion and ventilating cannot
beobstructedinanyway. Theindoorblower,evaporator
coil and filters must be inspected monthly.
2. Once each year, prior to the heating season, a
qualified technician must inspect all flue product carry-
ingareas ofthe furnaceand mainburners forcontinued
safe operation.
WARNING: At least once each year, a qualified ser-
vice technician should check out all of the items listed
under the servicing and trouble shooting and mainte-
nance section of this manual.
3. If the induced draft blower/motor assembly re-
quiresreplacement,an airtight seal betweentheblower
housing and the burner box must be restored. High
temperature silicone sealant must be used to ensure a
good seal.
4. GAS BURNERS
THE BURNERS SHOULD NEVER REQUIRE
CLEANING.
If cleaning is necessary, it indicates faulty operation of
theunit. Thecleaningshouldbedoneonlybyaqualified
serviceagencyafterconsultationwithanAAONService
Representative.
If the gas burners require cleaning, call an AAON Service
Engineer at [phone].
5. HEAT EXCHANGER
The necessity for cleaning the exchanger could indicate
faulty operation and should be checked only by a quali-
fied service agency after they have discussed the prob-
lem with a Service Representative.
Heat Exchanger prior to installation in unit.
Combustion Motor Flue Outlet
Burner Assembly
Manifold
Burner
Horn (typ)
Flame Sensor
Spark Rod

13
PERIODIC INSPECTION PROCEDURES Continued
COOLING
1. Main Power Switches are on and power is to the unit.
2. Set thermostat in cooling mode and place the "fan"
switch to on. Check blower for correct operating
direction, amperage and voltage.
3. PACKAGED UNITS - Check compressor operation.
Check the amperage and compare to the nameplate
data (check amperage load side of the compressor
contactor).
4. DX COIL UNITS / AIR HANDLERS - If a remote
condenserisapplicable,inspectionsandservicemust
followed according to the manufacturer's instruc-
tions and recommendations.
5. CHILLED WATER UNITS - Check remote chiller
operations according to the manufacturers instruc-
tions.Checkcoolantflowvalvesforcorrectoperation
and settings.
HEATING • NATURAL GAS
1. Before turning on the main electrical power switch,
besurethat all gassupplylineshave been purgedof
air.
2. Turn gas valve to "ON" position.
3. Turn main electrical power switch to "ON" and set
the thermostat to call for heat. The vent motor
should operate. The control will automatically
supply energy to the spark gap and the gas valve
after the thermostat contact closes.
4. Thesensing probe detectsthe presence oftheflame.
(Should no flame be detected in 10 seconds, the
ignition system will recycle. If no flame is detected
in 3 tries, the ignition system will lockout).
5. Adjust thermostat to a low temperature setting to
open contacts. The main gas flames should be
extinguished.
NOTE: The evaporator blower is controlled by the
ignition system. In the fan "Auto" mode the blower
comes on 45 seconds after flame is proved and goes off
120 seconds after the thermostat opens.
HEATING • ELECTRIC
1. Set thermostat in the heat mode.
2. Set thermostat to call for heat to engage all electric
heat strips. Check blower for proper rotation and
voltage.
3. Measure the amperage and voltage. Compare them
to the nameplate data.
HEATING • STEAM OR HOT WATER
1. Set thermostat in the heat mode.
2. Checksupplyblowerforproperrotationandvoltage.
3. Checkboilerorhotwateroperationsaccordingtothe
manufacturer's instructions and recommendations.
4. Check control flow valves for correct operation and
settings according to the manufacturer's instruc-
tions and recommendations.
ELECTRIC, STEAM, HOT WATER, COOLING &
CHILLED WATER UNITS
1. Blower,coilsandfiltersshouldbeinspectedmonthly.
2. Once a year, before unit is turned on for the heating
season,aqualifiedservicetechnicianshouldinspect
the unit for proper operation.
3. All valves and steam traps should be inspected
according to the manufacturer's instructions and
recommendations.
WARNING: All of the items listed under the service,
troubleshootingandmaintenancesectionofthismanual
should be performed once a year.
▲
! CAUTION
Before leaving installation, a complete
operating cycle should be observed
to verify that all components
are functioning properly.

14
SERVICING, TROUBLE SHOOTING & MAINTENANCE
LUBRICATION
All original blower motors and bearings are furnished
with an orginal factory charge of lubrication. Some
applications will require that bearings be re-lubricated
periodically. The schedule will depend on the operating
duty,temperaturevariationsorotherharshatmospheric
conditions.
Bearings should be re-lubricated when at normal oper-
ating temperatures, but not during operation. Rotate
the fan shaft manually and add minimum lubricant
requiredtopurgetheseals. DONOTOVERLUBRICATE.
Recommended lubricants are:
SHELL OIL - DOLIUM R
CHEVRON OIL - SRI No. 2
TEXACO INC. - PREMIUM RB
SERVICE
If the unit does not function properly and service is
required, service technicians qualified and experienced
in both gas, electric heating and air conditioning are
permittedtoprovideservicetokeepwarrantiesineffect.
The service technician should call the factory if assis-
tance is required.
SERVICE TECHNICIAN MUST PROVIDE THE
MODEL AND SERIAL NUMBER OF THE SPECIFIC
UNIT TO CUSTOMER SERVICE TO ASSURE A COR-
RECT DIAGNOSIS.
AAON, Inc.
Phone: [phone]
Fax: [phone]
Customer Service Department
COMMON CAUSES OF REDUCED AIR FLOW
A. DIRTYFILTERS-Filtersmustbeinspectedand
replacedon aregular basis. It isstrongly recommended
that the media be replaced monthly. Clean filters are
your best protection against premature system break-
down.
Do not operate the unit without the filters in place.
Operation of the unit without filters will result in a
clogged evaporator coil - a very expensive service prob-
lem to resolve.
B. OBSTRUCTION TO AIR FLOW - Supply and
return air grilles must be kept clear so air can be freely
discharged from and drawn into the system.
CLEANING
Inspect unit interior at the beginning of each heating
and cooling season and as operating conditions require.
COILS
Evaporator coil(s) should be inspected and cleaned an-
nually to ensure there is no obstruction to air flow.
Condenser coil(s) should be inspected monthly. Clean
condenser coils annually or as required by location and
outdoor air conditions.
CONDENSATE DRAIN
Check and clean annually at start of cooling season.
BLOWER
Inspect blower and blower section to keep free of dust or
debris.
TURN OFF POWER BEFORE ATTEMPTING TO
CLEAN BLOWER WHEEL.
▲
! WARNING
ELECTRIC SHOCK HAZARD.
Shut off all electrical power to unit to avoid
shock hazard or injury from rotating parts.
Typical slide-out blower section

15
Before inspecting or replacing the filters, be sure the
unit IS NOT operating. The filters are located in the
filter access section of the unit. Open filter access door,
and pull filters straight out to inspect. Inspect ALL
filters each time. Replace filters with the size indicated
oneachfilterorasshowninthefilterchartbelow. Arrow
on replacement filters must point towards the blower.
Monthly inspection is required to maintain optimum
efficiency.
NOTE: CHARTREFLECTSSTANDARDFACTORYSUPPLIEDFILTERSANDSIZES.
CONTACTFACTORYFORSPECIALOPTIONALFILTERPACKAGES.
FILTERS
FILTERS SHOULD BE REPLACED EVERY 30 DAYS OR AS REQUIRED.
FILTER SIZE UNIT SIZE
16" x 20"
Standard 2" Throwaway 46
4
2 - 5 6 & 7 8 & 10 13 & 15 16 - 30
16" x 20"
Optional 2" or 4" Pleated
20" x 25"
Optional 2" or 4" Pleated
66
46
IT IS IMPORTANT TO KEEP COILS, BLOWERAND FILTERS CLEAN !
FILTER INSTALLATION / REPLACEMENT
▲
! WARNING
Before attempting to perform any service
or maintenance, turn the electrical power
to unit to OFF at disconnect switch(es).
Unit may have multiple power supplies.
Slide-out
filters
Optional
Economizer
Optional R/A
smoke detector
location

16
BURNER GOES "OFF" ON HIGH LIMIT
SERVICING
TROUBLE POSSIBLE CAUSE
ELECTRIC HEATING
SYSTEM OFF 1. Check power at line side of contactor(s).
2. Thermostat not set for heating.
1. Overload relay tripped.
2. Heater Relay not energized.
3. Blower Contactor not energized.
4. Capacitor shorted or open (PSC motors only).
1. Blower running backwards.
2. Dirty air filters.
3. Dirty coils.
4. Duct obstruction.
5. Belts loose (if applicable).
1. One or more heater contactors are open.
2. Limit switches are open.
3. Heater relay open.
4. Heat strips burned out.
BLOWER DOESN'T DELIVER AIR
EVAPORATOR MOTOR WILL NOT RUN
1. Check power and gas supply.
2. Check thermostat switches and settings.
3. Check 24 volt power to ignition control.
1. Check for power at main gas valve.
2. Defective gas valve.
3. Loose or broken connection to gas valve.
4. Check limit controls for open.
5. Check continuity of differential pressure switch with motor
turning. If open, replace differential pressure switch.
6. Defective ignition control.
1. Thermostat not calling for heat.
2. Relay not closing. (No power to motor)
3. Motor stuck or winding open.
4. Internal motor overload open.
1. Unit blower not coming on. (Check fan control)
2. Blower motor running backward.
3. Filters dirty.
4. Ducts obstructed or dampers closed.
5. Manifold gas pressure too high.
1. Hand valve "off" (turn to on)(main gas valve).
2. Gas off or very low pressure.
3. Check for power at main gas valve.
4. Check continuity of differential pressure switch with motor
turning. If open, replace differential pressure switch.
5. Sparker sensor out of adjustment.
6. Main orifice blocked.
1. Defective Ignition Control.
2. See cooling trouble shooting page 19.
SYSTEM OFF
BLOWER COMES ON, BUT LITTLE OR NO
HEAT
IGNITION ON, BURNER WON'T LIGHT
GAS HEATING
COMBUSTION AIR BLOWER WON'T RUN
BURNER WON'T COME ON
SUPPLY FAN BLOWER WON'T RUN

17
TROUBLE POSSIBLE CAUSE
STEAM AND HOT WATER HEATING
1. Check power at line side of contactor(s).
2. Thermostat not set for heating.
1. Overload relay tripped.
2. Heater Relay not energized.
3. Blower Contactor not energized.
1. Blower running backwards.
2. Dirty air filters.
3. Dirty coils.
4. Duct obstruction.
5. Belts loose (if applicable).
1. Check steam traps, valves, and steam or hot water
supply in accordance with manufactures instructions.
2. Faulty thermostat.
SYSTEM OFF
SERVICING Continued
BLOWER MOTOR WILL NOT RUN
BLOWER DOESN'T DELIVER AIR
BLOWER COMES ON, BUT LITTLE OR NO HEAT
FAN MOTOR RUNS HOT AND CUTS OUT
1. Check power at lineside of contactor(s).
2. Thermostat not set for cooling.
3. High pressure control tripped.
4. Low pressure switch open (loss of charge).
1. Overload thermal protector open in motor.
2. Motor run capacitor open or shorted.
3. Motor failed.
4. Fan or shaft stuck.
1. Overload thermal protector open in motor.
2. Relay not closing.
3. Motor failed.
4. Capacitor shorted or open (PSC motors only).
5. Stuck shaft or blower wheel.
1. Check for low refrigeration charge.
2. Compressor overload setting.
3. Ambient temperature too low.
4. Filters dirty or air flow restricted.
5. Evaporator blower not running.
1. Line voltage too high.
1. Line voltage too low.
2. Limit switches are open.
3. Overload or pressure control tripped.
1. Blower running backwards.
2. Dirty filters.
3. Duct obstruction.
4. Belts loose (if applicable).
SYSTEM OFF
REFER TO MFG'S
INSTRUCTIONS
IF REMOTE
CONDENSER
BLOWER DOES NOT DELIVER AIR
COMPRESSOR WILL NOT START
COMPRESSOR SHORT CYCLES
EVAPORATOR BLOWER WILL NOT RUN
CONDENSER FAN WILL NOT RUN
REFER TO MFG'S
INSTRUCTIONS
IF REMOTE
CONDENSER
REFER TO MFG'S
INSTRUCTIONS
IF REMOTE
CONDENSER
COOLING PACKAGE and UNITS with REMOTE CONDENSERS

18
TROUBLE POSSIBLE CAUSE
1. Check power at line side of contactor(s).
2. Thermostat not set for cooling.
1. Overload thermal protector open in motor.
2. Contactor not closing.
3. Motor failed.
1. Line voltage too high.
1. Blower running backwards.
2. Dirty air filters.
3. Duct obstruction.
4. Belt loose (if applicable).
1. Check supply water and temperature.
2. Check water control valves operation.
3. Check water temperature rise entering and leaving
unit to determine if adequate water is flowing.
SYSTEM OFF
SERVICING Continued
COOLING - CHILLED WATER
EVAPORATOR BLOWER WILL NOT RUN
ROOFTOP UNIT REPLACEMENT PARTS
Replacementparts for AAONequipmentmay be obtainedfromAAON. When ordering parts,alwaysreference the
unit model number, serial number and part number.
AAON, Inc.
Customer Service Department
2425 South YukonAve • Tulsa, Oklahoma 74107
Phone: [phone] • Fax: [phone]
ALWAYS USE AAON SPECIFIED PARTS
FAN MOTOR RUNS HOT AND CUTS OUT
BLOWER DOES NOT DELIVER AIR
BLOWER COMES ON, BUT LITTLE OR NO
COOLING

19
SEQUENCE OF OPERATIONS
I. GENERAL INFORMATION
A. HEATING
1. Natural Gas
When the thermostat calls for heating, W1 makes R to
the heat relay (HR). All N.O. (Normally open) contacts
close and all N.C. (normally closed) contacts open. The
combustionmotorstartsandasthepressuredecreasesin
the flue outlet box the ignition control is energized. The
control sends 24 VAC to the main gas valve and high
voltagetotheignitor. Ifaburnerflamehasbeendetected
after10seconds,thesparkisextinguishedandtheflame
continues. If a flame has not been detected after 10
seconds, the gas valve closes, the spark ceases and the
induced draft blower continues to purge the heat ex-
changer. After 45 seconds of purge, the ignition system
willattempt tolight theburners again. Shouldno flame
bedetectedafter3attempts,theignitioncontrollocksout
the system.
On a fault the gas train is shut down by a main limit
switch located in the heat exchanger area or by an
auxiliary limit mounted in the supply air fan housing.
2. LP (Propane) Gas
The sequence for LP Gas is the same as above but upon
non-proof of burner the gas train will enter a 100%
lockout condition.
3. Electric
When the thermostat calls for heat 'W1' makes 'R' to the
heat relay 'HR'. All N.O. contacts close, and all N.C.
contactsopen. Theheatrelaymakes'R' tothefirststage
of electric heat.
On a fault condition the main limit located in the supply
air or the auxiliary limit located in thesupply air fan
housing will remove power from all contactors.
Ifadditionalheating is requiredasecond set ofelements
can be turned on by 'W2'.
OPTIONAL - When available the electric heat can be
sequenced to provide a constant discharge air tempera-
ture.
4. Steam or Hot Water
This option adds a steam coil down stream of the cooling
coil (if supplied). Connections and controls are provided
by others.
B. COOLING
1. Packaged Units
Whenthethermostatcallsforcoolingfromthespace,'Y1'
makes'R'to'CC1'throughtheLPS(lowpressureswitch),
HPS (high pressure switch) and optional GOT (guaran-
tee off timer).
2. DX Only - Coil Units
Whenthethermostatcallsforcoolingfromthespace,the
condensing unit is energized (refer to manufacturers
instructions for sequence of operation). The evaporator
blower contactor is energized simultaneously with the
condensing section.
3. Chilled Water Coil Units
Theblowercontactorisenergizedtoprovidesupplyairon
asignalfromthespacethermostat. Allothercontrolsare
by others.
C. OPTIONAL ECONOMIZER
When cooling is called for and the unit has the econo-
mizer option installed, temperature switch ECS (or En-
thalpy) allows the economizer operation when the out-
sideairreachestherequiredsetpoint. (Someoptionsuse
dry bulb sensing and some options use enthalpy sensing
to determine the outside air (O.A.) condition).
When the economizer is in operation 'Y1' controls the
opening and closing of the dampers, 'Y2' is then able to
control the compressors which 'Y1' normally controls. A
modulating economizer is also available. The operation
is the same as the standard economizer except that the
motor modulates the damper position to maintain a
preset mixed air temperature.

20
II. VAV (Variable Air Volume) SYSTEMS
NOTE: VAV BOXES AND CONTROLS ARE
SUPPLIEDBYOTHERSFORFIELDINSTALLATION.
When a call for cooling is received, the controller board
stages on compressors to maintain a field set supply air
temperature. As different zones become satisfied their
VAV boxeswillclose. Thisinturncausesthesupplyduct
pressure to rise. The VAV controller board senses this
increaseinpressureandmodulates the supplyfanspeed
to maintain the required field set supply air pressure
setpoint.
Normally VAV units are cooling only units. There are
certain applications where electric or gas heat is used to
provide morning warmup. When gas or electric heat is
usedformorningwarmuptheairflowwillnotbe allowed
tovary. Thefanspeedcontrolwillbedisableduntilacall
for cooling is received, then the heating system will be
locked out and VAV will be enabled.
III. POWER EXHAUST OPTIONS
When space over pressurization occurs, due to econo-
mizer operation, a power exhaust will be utilized to
provide relief.
A. When three position economizer is called for, an
On/Off power exhaust will be used.
POWER EXHAUST w/ 3 POSITION ECON.
In the unit "OFF" or in the minimum economizer
position,thepowerexhaustfanisoff. Whentheunit
goes to 100% outside air operation, the power
exhaust fan motor starts and operates until the unit
is shut off or the economizer goes back to minimum
position.
The end switch located on the economizer outside air
dampersection,isfieldadjustabletoallowfordifferences
in building design. The switch engages and disengages
thepowerexhaustmotor(s)throughacontactor. Theend
switch is included in the 24 VAC circuit.
B. Fullmodulatingeconomizer,afullmodulatingpower
exhaust will control the amount of actual exhausted
air by means of a building sensing pressure control
which opens or closes according to desired pressure
in the space.
POWEREXHAUSTw/FULLMODULATINGECON.
In the unit "OFF" or in the minimum economizer
position,thepowerexhaust isoff. Astheeconomizer
begins to modulate open, an end switch (adjustable)
closes which starts the power exhaust fan motor.
The power exhaust operates until the economizer
modulatesbelowtheendswitch setting ortheunitis
shut off.
POWER EXHAUST w/ FULL MODULATING ECON.
WITH BUILDING PRESSURE CONTROL
Intheunit"OFF"orintheminimumeconomizerposition
the power exhaust is off. As the economizer begins to
modulate open, an end switch (adjustable) closes which
starts the power exhaust fan motor. The amount of
exhaust air is controlled by a set of dampers in response
to the unit mounted building static pressure controller.
Thepower exhaustoperates untiltheeconomizermodu-
lates below the end switch setting or the unit is shut off.
(NOTE: Static pressure sensing tubing is field supplied
and installed).
SEQUENCE OF OPERATIONS Continued