A\C compressor stops; won't restart until system down for 5 min.

nick_shirleyMay 22, 2013

I have a Bryant\Day & Night 568D compressor, a BDP 518A air handler, and a Honeywell TH6000 thermostat. It cools just fine but periodically the compressor will stop on its own (or maybe doesn't kick back on when the thermostat says go) even when the room temp is high enough to trigger the system. During these times, the blower is still blowing (albeit just recirculating warm room air) and the thermostat's display looks normal, with a solid "cool on" message.

What is strange is that all it takes is for me to turn the thermostat to off for about five minutes. When I turn it back on to the cool setting, everything works just fine. It'll stay working as needed for a couple of days, then I'll notice that the compressor fan isn't turning even though the blower is running.

Is this a thermostat problem? I realize that there is a compressor protection feature that keeps the compressor off for a while if the restart is right after the last shut down, but when that feature kicks in for a few minutes, the "cool on" display flashes and the blower is temporarily disabled. That's not happening here.

Where else might this problem lie? Is there a self-resetting circuit breaker in this compressor that opens under stress but won't reset until all juice is turned off to the system?

Thanks for any help you can provide!

Nick in Palm Springs

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brickeyee

Restart protection in the thermostat or condenser.

It waits to turn on until the high side pressure has dropped down to help unload the compressor at start up.

    Bookmark   May 22, 2013 at 2:35PM
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nick_shirley

Yeah, I know about the restart protection in the thermostat, as the original post indicated. But when this problem occurs (the thermostat kicking in only triggers the blower and not the compressor), the high side pressure has been down for quite some time. I can turn the temp setting on the thermostat high enough that the A\C system is on standby for hours, but when I subsequently drop the setting down, only the blower runs. It's only when I turn the thermostat from "cool" to "off" and wait 10 minutes that the system runs correctly when I set it to "cool" again. How would this indicate that the restart protection is at fault?

    Bookmark   May 23, 2013 at 3:40PM
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brickeyee

Could be as simple as a bad timer relay on the high side sensor.

Could be a bad controller board in part of the system.

    Bookmark   May 24, 2013 at 1:13PM
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Todd55

Nick - I have the exact same problem. I am using a Honeywell CT3500 programmable thermostat that is about nine years old. This problem only occurs very infrequently and I believe that it is just that the compressor doesn't kick on when the thermostat says go ( I do not think that it is the compressor stopping on its own).
My concern is that if this happens while we are away for an extended period of time, could this do damage to the compressor if left in this state? (As you probably know when this occurs the blower just keeps going and never shuts off because the temperature is never lowered.)

I am going to replace my thermostat with a new Honeywell RTH2300B and see if this problem happens again. I will post my results, but it might take a long time till I know definitively if it was the thermostat. Please let me know if you find out anything new on your end. Thanks, Todd

    Bookmark   June 25, 2013 at 10:35AM
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Todd55

Well the new thermostat did not solve the problem. I had my AC guy come out and he showed me that the contacts on the contactor were slightly burnt and that even though it was pulling down, it was not making good contact at times. We have had to replace the contactor a few times in the past. This time he installed a new type of computer controlled contactor that was designed to reduce arcing and thus should have a longer lifetime. This device is an Emerson-White Rodgers 49P11-843 SureSwitch. (Cost is around 50-60 dollars on Amazon). So far this has worked very well.

    Bookmark   August 26, 2013 at 1:32PM
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