AEC ACOA Series Air-Cooled Central Chillers - Manual (Page 29)

Step 1
4. Opstat 4TAS-1 opens as water temperature reaches minimum set point. Liquid line
solenoid 1SOL de-energizes and Circuit 1 refrigerant flow stops. Relay 8CR de-
energizes, removing 4PS-1 bypass ( 4PS-1 now controls pumpdown). Compressor 1
remains running and Circuit 1 pumpdown begins.
5. When suction pressure drops to the pumpdown limit, 4PS-1 opens and Compressor 1
stops. Circuit 1 pumpdown and unload sequence is now complete, and all Circuit 1
controls are back to standby status.
Figure 11
ACOA Control Settings and Set Points (Unit is Off)
ACOA Control Settings
Time Delay
1TR-1 & 2 5 Min.
3PS-1 & 2 120 Sec.
9PS-1 & 2 120 Sec.
4TR-2 10 Sec.
5TR-1 & 2 2 Min.
Pressure (PSIG) Open Close
1PS-1 & 2 360
10, 11PS-1 140 190
10, 11PS-2 160 21-0
10, 11PS-3 170 230
Temperature Open Close
4TAS-1 LWT + .40R LWT + .55R
4TAS-2 LWT + .55R LWT + .70R
4TAS-3 LWT + .70R LWT + .85R
4TAS-4 LWT + .85R LWT + R
3TAS 40ºF 43ºF
ACOA Set Points
Percentage
of ethylene
Minimum
ambient
Minimum
9PS open
4PS
open
4PS
close
Minimum
2TAS open
glycol ºF ºC psig kPa psig kPa psig kPa ºF ºC
0% 32ºF 0ºC 55 psig 379 kPa 45 psig 310 kPa 70 psig 483 kPa 38ºF 3ºC
10% 27ºF -3ºC 49 psig 338 kPa 39 psig 269 kPa 64 psig 441 kPa 33ºF 1ºC
20% 18ºF -8ºC 39 psig 269 kPa 29 psig 200 kPa 54 psig 372 kPa 24ºF -4ºC
30% 3ºF -16ºC 33 psig 228 kPa 23 psig 159 kPa 48 psig 331 kPa 9ºF -13ºC
40% -13ºF -25ºC 33 psig 228 kPa 23 psig 159 kPa 48 psig 331 kPa -7ºF -22ºC
50% -20ºF -29ºC 33 psig 228 kPa 23 psig 159 kPa 48 psig 331 kPa -14ºF -26ºC
Caution!
Do not set 9PS, 4PS, or 2TAS lower than indicated for your glycol concentration—
the AEC, Inc. warranty is voided! The AEC, Inc. warranty does not cover freeze-up!
Figure 12
Page 28
ACOA Series Air-Cooled Central Chillers