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Unit Controls
TABLE 17 – DISCHARGE AIR TEMPERATURE CONTROL FOR 6 COMPRESSORS (8 STEPS)
LEAD SYSTEM
*STEP
COMP 1
0
OFF
1
ON+HG
2
ON
3
ON
4
ON
5
ON
6
ON
7
ON
8
ON
* STEP can be viewed using the OPER DATA key and scrolling to COOLING DEMAND.
TABLE 18 – DISCHARGE AIR TEMPERATURE CONTROL FOR 4 COMPRESSORS (6 STEPS)
LEAD SYSTEM
*STEP
COMP 1
0
OFF
1
ON+HG
2
ON
3
ON
4
ON
5
ON
6
ON
* STEP can be viewed using the OPER DATA key and scrolling to COOLING DEMAND.
TABLE 19 – DISCHARGE AIR TEMPERATURE CONTROL FOR 3 COMPRESSORS (SINGLE SYSTEM)
*STEP
COMP 1
0
OFF
1
ON+HG
2
ON
3
ON
4
ON
* STEP can be viewed using the OPER DATA key and scrolling to COOLING DEMAND.
TABLE 20 – DISCHARGE AIR TEMPERATURE CONTROL FOR 2 COMPRESSORS (SINGLE SYSTEM)
*STEP
COMP 1
0
OFF
1
ON+HG
2
ON
3
ON
* STEP can be viewed using the OPER DATA key and scrolling to COOLING DEMAND.
Notes:
1. Step 1 is Hot Gas Bypass and is skipped when loading occurs. Hot Gas Bypass operation is inhibited during Pumpdown. For Discharge
Air Temperature Control the Hot Gas Bypass solenoid is energized only when the lead compressor is running and the DAT < SP, the Hot
Gas Bypass solenoid is turned off when the DAT > SP + CR/2.
2. Step 3 is skipped when loading occurs.
3. Step 4 is skipped when unloading occurs.
122
COMP 2
COMP 3
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
ON
OFF
ON
OFF
ON
OFF
ON
ON
ON
ON
COMP 2
OFF
OFF
OFF
OFF
ON
ON
ON
COMP 2
COMP 3
OFF
OFF
OFF
OFF
SEE NOTE 1
OFF
OFF
ON
OFF
ON
ON
COMP 2
OFF
OFF
SEE NOTE 1
OFF
ON
COMP 1
OFF
SEE NOTE 1
OFF
OFF
SEE NOTE 2
ON
SEE NOTE 3
OFF
ON
ON
ON
ON
COMP 1
OFF
SEE NOTE 1
OFF
OFF
SEE NOTE 2
ON
SEE NOTE 3
OFF
ON
ON
LAG SYSTEM
COMP 2
COMP 3
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
ON
OFF
ON
OFF
ON
ON
LAG SYSTEM
COMP 2
OFF
OFF
OFF
OFF
OFF
OFF
ON
YORK INTERNATIONAL
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