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#41799 - 09/09/04 05:47 PM A/C Question  
aldav53  Offline
Joined: Aug 2001
Posts: 545
Chandler, AZ USA
Not exactly electrical, but from past experience an air conditioner (heat pump) will not turn back on right away after it is shut off. There is a 2 min or so delay to protect the compressor. While checking the power to one today it would go on and off immediately with the breaker. Is this possibly normal on dfferent units?

Also the customer said the condenser fan motor would shut off while the compressor still ran at times? This doesn't seem right either.

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#41800 - 09/09/04 06:04 PM Re: A/C Question  
iwire  Offline
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
It could be normal or low on refrigerant.

On smaller AC units it is a thermal overload that trips out when you try to do a quick restart. This happens because the gas pressure against the piston will not allow the motor to turn crating a locked rotor condition.

On larger units there is an actual timer to prevent short cycling.

[This message has been edited by iwire (edited 09-09-2004).]

Bob Badger
Construction & Maintenance Electrician

#41801 - 09/09/04 08:02 PM Re: A/C Question  
twh  Offline
Joined: Mar 2004
Posts: 916
Regina, Sask.
I don't think I've seen a compressor run without the condenser - at least on an air conditioner.

#41802 - 09/09/04 08:16 PM Re: A/C Question  
iwire  Offline
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
If the condenser is equipped for running in low ambient temperatures it may cycle or even be speed controlled.

Or you may just have a bad condenser fan motor that is cycling on the thermal protection. If that is what is happening the compressor will usually kick off shortly after.

Bob Badger
Construction & Maintenance Electrician

#41803 - 09/09/04 08:20 PM Re: A/C Question  
electricman2  Offline
Joined: Nov 2003
Posts: 269
Thomasville, NC USA
If it is a heat pump it is normal for the condenser fan to shut off and the compressor remain on when in the defrost cycle in the heating mode. If not a heat pump possibly the thermal overload in the fan motor is opening for some reason.
Sometimes the 2 minute or so delay is in the thermostat so opening and closing the circuit breaker would start and stop unit with no delay.


#41804 - 09/10/04 12:41 AM Re: A/C Question  
aldav53  Offline
Joined: Aug 2001
Posts: 545
Chandler, AZ USA
It is a heat pump, but the defrost cycle is not needed because it is still in the cooling mode until it reverses for winter in the heat mode.
Good point on that delay being in the thermostat, thats probably it.
The customers original complaint was that the A/C breaker trips 7 or 8 times a day and an A/C guy check it and said it was ok.
Its still hot here in AZ so it runs a lot still.

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#41805 - 09/10/04 05:48 AM Re: A/C Question  
maintenanceguy  Offline
Joined: Dec 2001
Posts: 300
Southern NJ, USA
Some ac/s have delay on break timers that start timing when electric is turned off, some have delay on make timers that start counting when electricity is turned on. Most residential ac/s don't have any timers at all.

And some ac/s (heat pumps too) have a condenser fan that cycles on and off to maintain a constant condenser coil temperature. The fan runs less often on a cool day than it does on a hot day. If so, the common wire to the fan motor would go through a pressure switch located somewhere on copper lines going to the condenser coil.

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