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UNIT OPERATION - 7-1/2, 10 & 12-1/2 TON
When the external control calls for cooling at terminal Y1:
1. The system controller (SC) is energized. The system con
-
troller starts the compressors and enables the condenser
fans byenergizing contactor1M (and2M onthe 12-1/2ton,
208/230 volt models).
Thesingle condenserfan isenergized withthe compressor
on the 7-1/2 ton models.
Condenserfan motor#1 isenergizedwith thecompressors
on the 10 and 12-1/2 ton models while fan #2 is enabled
with compressor operation. Fan motor #2 operation iscon
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trolled through the Ambient Temperature Switch (ATS)
which will de-energize the motor when the ambient tem
-
perature falls below 70°F.
2. Safety Lockout: The system controller (SC) has a lockout
circuitto preventcompressor short-cyclingon asafety con
-
trol with automatic reset. If the high or low refrigerant pres
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sure switches (HP or LP) open, the SC will enter lockout
mode.
SCprovidesa90second bypassofthelow pressureswitch
LP to prevent nuisance lockouts during unit start-up.
Amalfunctionlight (24V,2 Amax.resistive load)can been
-
ergized throughSC, byconnecting thelight betweentermi
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nals X and B on TB1. Terminal X will energize when SC
locks out.
3. Unit is equipped with an anti-short cycle timer to prevent
two successive compressor starts within 5 minutes. If the
compressorfails tostartwith acallfor coolingand SCis not
lockedout, wailatleast 6minutesfor theanti-cycle timer to
reset.
NOTE: To reset the unit after a lockout:
A. Turn the system switch on the thermostat to the “OFF”
position and back to the “COOL” position.
OR
B. Increasetheset pointofthe roomthermostat abovethe
temperature inthe conditionedspace and returnit toits
original setting.
035-15407-002-B-0404
14 Unitary Products Group
CRANKCASE HEATER
The crankcase heaters mustbe energized at least 8 hours bef
-
ore starting the compressor. To energize the crankcase heat
-
ers, the main disconnect switch must be closed. During this 8
hour period,the systemswitch on theroom thermostatmust be
“OFF” to prevent the compressor from starting.
CAUTION: DO NOT ATTEMPT TO START THE COMPRES
-
SOR WITHOUTAT LEAST8 HOURSOF CRANK
-
CASE HEAT OR COMPRESSOR DAMAGE WILL
OCCUR.
Make sure that the bottom of the compressor is warm to the
touch to prove crankcase heater operation.
PRE-START CHECK
Before starting the unit, complete the following check list:
1. Have sufficient clearances been provided?
2. Has all foreign matter beenremoved from the interior ofthe
unit (tools, construction or shipping materials, etc.)?
3. Have the condenser fans been rotated manually to check
for free rotation?
4. Are all wiring connections tight?
5. Does the available power supply agree with the nameplate
data on the unit?
6. Isthecontrolcircuittransformersetforthepropervoltage?
7. Have the fuses, disconnect switch and power wire been
sized properly?
8. Are all compressor hold-down nuts properly secured?
9. Are any refrigerant lines touching each other or any sheet
metal surface? Rubbing due to vibration could cause a re
-
frigerant leak.
10. Are there any visible signs of a refrigerant leak, such as oil
residue?
11. Is any electrical wire laying against a hot refrigerant line?
INITIAL START-UP
1. Supply power to the unit through the disconnect switch at
least 8 hours prior to starting the compressor.
2. Move the system switch on the thermostat to the AUTO or
COOL position.
3. Reduce the setting of the room thermostat to energize the
compressor.
4. Check the operation of the evaporator unit per the manufac
-
turer's recommendations.
5. With an ammeter, check the compressor amps against the
unit data plate.
6. Check for refrigerant leaks.
7. Check for any abnormal noises and/or vibrations, and make
the necessary adjustments to correct (e.g. fan blade(s)
touchingshroud,refrigerantlineshittingonsheetmetal,etc.)
8. Afterthe unithasbeenoperatingfor severalminutes,shutoff
the main power supply at the disconnect switch and inspect
all factory wiring connections and bolted surfaces for tight-
ness.
CAUTION: DO NOT ATTEMPT TO START THE COMPRES-
SOR WITHOUT AT LEAST 8 HOURS OF CRANK-
CASE HEAT OR COMPRESSOR DAMAGE WILL
OCCUR.
OPERATION
SECURE OWNER'S APPROVAL: When the system is functioning properly, secure the owner's approval. Show him
the location of all disconnect switches and the thermostat. Teach him how to start and stop the unit and how to adjust
temperature settings within the limitations of the system.
START-UP