The compressor of an ACSC100 does not cycle on and off, only stays "on"

[Anonymous user]

We have an ACSC100 unit, "Spot" type configuration, has been alarmed by: "Rack inlet high temperature violation", "high discharge pressure alarm", "persistent high discharge pressure alarm" and "supply air high temperature violation" and the equipment stays in "Idle" condition. We reset the equipment and it works, Pressures: Suction: 154 PSI, discharge: 389 PSI, and the compressor don't off, does not cycle on and off. This condition is maintained until the Inrow returns to "idle" condition.

The rack inlet temperature sensor it works normally also the mechanical part of the equipment (compressor, pipes, etc) appears to be fine. The Heat load of the room is an APC PDU with transformers.

What could be the cause of the problem, the control card? 

[BillP]

Hello Ivan.

How long does the unit run for before it goes into high discharge pressure alarm? What does the discharge pressure go to right before it goes into high discharge pressure alarm? What is the cooling demand show on the unit while it is running?

Thank you

[Anonymous user]

Hi, the unit began to go to the high discharge pressure alarm every 5 or 4 hours. the cool demand was between 3 to 4.8 kw but the compressor did'nt stop. On sunday we changed the control board from the user interface box from another same model Inrow and the equipment works normally performing the normal compressor "on and off" cycle. But today appears this problem: the equipment goes to idle condition again by high discharge pressure, appears this alarm: "startup line pressure imbalance alarm" and the discharge pressure goes to 540 PSI meanwhile the suction pressure is: 164 PSI. We adjust the pressures, we discovered that a pressure sensor from the suction line was incorrectly placed (did'nt make contact) and we repaired it, the equipment works but when we turn it off and start again , it goes to idle condition because the discharge pressure goes high again. We turn it off the equipment and when start again the compressor turns on even the equipment is on stand by condition.

Regards

[BillP · Accepted solution]

Hello Ivan.

If the compressor is staying on with the unit in standby, check the compressor relay. It may be getting stuck closed. There is 208 volts going to the relay so a qualified HVAC tech will need to check the relay. 

Thank you