Figure 26 - Discharge Air Temperature Control; Table 16 - Discharge Air Temperature Control For 5 And 6 Compressors (7 And 8 Steps); Table 17 - Discharge Air Temperature Control For 4 Compressors (6 Steps) - York YLUA0248 Series Installation Operation & Maintenance

SECTION 8 – UNIT OPERATION
20 sec.
unloading
51.5°F
(10.8°C)

FIGURE 26 - DISCHARGE AIR TEMPERATURE CONTROL

TABLE 16 - DISCHARGE AIR TEMPERATURE CONTROL FOR 5 AND 6 COMPRESSORS (7 AND 8 STEPS)

LEAD SYSTEM (Sequence - SEE NOTE 4)
* STEP COMP 1
0 OFF
1 ON+HG
2 ON
3 ON
4 ON
5 ON
6 ON
7 ON
8 ON
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.
* STEP can be viewed using the OPER DATA key and scrolling to COOLING DEMAND.
4. Each system will attempt to rotate the lead compressor start sequence to help even out the run hours in a system, therefore piping suction
risers should be sized off the smallest compressor capacity in either system.

TABLE 17 - DISCHARGE AIR TEMPERATURE CONTROL FOR 4 COMPRESSORS (6 STEPS)

LEAD SYSTEM (Sequence - SEE NOTE 4)
* STEP COMP 1
0 OFF
1 ON+HG
2
3
4
5
6
* 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.
* STEP can be viewed using the OPER DATA key and scrolling to COOLING DEMAND.
4. Each system will attempt to rotate the lead compressor start sequence to help even out the run hours in a system, therefore piping suction
risers should be sized off the smallest compressor capacity in either system.
126
30 sec. 60 sec.
unloading unloading
52.5°F
(11.4°C)
Discharge Air Temperature Control – Compressor Staging
Setpoint = 55.0°F (12.8°C) Range = +/- 5°F (-12.2°C)
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
ON OFF
ON OFF
ON ON
ON ON
ON ON
control range
(no compressor staging)
53.0°F 55.0°F
(11.7°C) (12.8°C)
Low Limit Setpoint High limit
LAG SYSTEM (Sequence - SEE NOTE 4)
COMP 1
OFF
OFF
SEE NOTE 1
OFF
ON
SEE NOTE 2
SEE NOTE 3 OFF
ON
ON
ON
ON
LAG SYSTEM (Sequence - SEE NOTE 4)
COMP 1
SEE NOTE 1
SEE NOTE 2
SEE NOTE 3
FORM 150.73-NM2
ISSUE DATE: 09/07/2020
60 sec.
loading
57.0°
(13.9°C)
COMP 2 COMP 3
OFF
OFF
OFF
OFF
OFF
OFF
ON
ON
ON
COMP 2
OFF OFF
OFF OFF
OFF OFF
ON OFF
OFF OFF
ON OFF
ON ON
JOHNSON CONTROLS
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
ON