Heat pump not cooling or heating

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  #1  
Old 03-15-05, 08:07 PM
oanglade
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Heat pump not cooling or heating

Hi, I have a heat pump in my house in GA that is not cooling when set to cool or heating when set to heat. I'll post the brand/model in a little while (I'm at work right now).

Inside fan works, coils/fins are clean, filter is clean.

Air blows out of register just like always.

Outside unit: Fan turns on and I can hear what I believe is the "humming" of the current draw of the compressor. I could be wrong and it could be drawing current, but not starting, I guess. The breakers inside the house and next to the outside unit are not tripping.

Thermostat works.

Now, if I push the high pressure switch (red "reset" button near the outside lines, the outside fan will stop. If I let go, it starts again.

I have no experience with AC units or heat pumps, but I am an electrical engineer, very mechanically inclined and experienced do-it-yourselfer. If you explain it, I will understand it and be able to do it (given the parts and tools).

Any advice on what to check/test and how would be appreciated.
Thanks.

 

Last edited by oanglade; 03-24-05 at 07:28 AM.
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  #2  
Old 03-15-05, 08:16 PM
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has the Unit itself all the sudden stop cooling/heating, or has it slowly went down the hill?

If it's all the sudden, make sure the compressor itself is running. if it's running, then chances are you may of lost your charge.. Do any of the copper line feel cool/hot?
 
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Old 03-15-05, 09:14 PM
oanglade
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It's hard to tell if it happened all of a sudden, since the heat strips will kick in to heat if gets too cold, but I would guess that yeah, it was sudden. Normally, I can tell when the red reset button needs to be pressed because it will feel cold, even though the actual temp is the same as the set temp (when heating).

That's another thing: If we have a day where we need cooling during the day, but then heating at night, for sure we'll have to go and press the reset button. Even if the actual temp is under the set temp on the thermostat and the unit is not actually blowing when we switch from cooling to heating, plus it has a delay relay also.

It was close to 80 degrees here on Sunday and it definitely didn't cool then.
Yesterday it was in the 50s during the day and I noticed that the air blowing out wasn't warm.

The copper lines feel "ambient".
 
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Old 03-16-05, 05:59 AM
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If the copper line felt ambient when it should have been running then you're either low on refrigerant or the compressor is not starting. What I would suggest is to pull the disconnect and then remove the service panel and do a visual of the wires all the way to the compressor. If everything looks good you could ohm out the compressor and post what you get between S-R,S-C,R-C, and each one to ground.
 
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Old 03-16-05, 11:09 AM
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Wink

With Matt here did it run or not? Freon low a capacitor out short in compressor?

ED
 
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Old 03-16-05, 01:44 PM
oanglade
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Will do. I'll check to see if the compressor is in fact starting and if not, I'll ohm it out and post here after checking the wiring vs. the diagram.
 
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Old 03-16-05, 06:32 PM
rdoughty
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try this: take the cover off your system. unhook the outdoor fan from the fan relay if possible. activate the system. if you hear your compressor humming, then it has fell into rotor lock. what this means most of the time is the magnetic poles inside the compressor have reached an exact point with the core of the rotor and has created an equal magnetic field. activate your system and take a rubber mallet or something light and tap the compressor. this should throw it out of rotor lock. if not, try spinning the rotor shaft if possible. if those things don't work, try getting a 2 watt, 20,000 ohm resistor. take that resistor and discharge the compressor capacitor with all power disconnected. remove the capacitor and test the voltage on it. if it doesn't test a voltage, then try replacing that capacitor with a new one. if that doesn't work, then that possibly means the compressor is wearing out and it may be time to replace it.
 
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Old 03-18-05, 01:42 PM
oanglade
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I definitely hear the compressor "humming" every once in a while for about 5 seconds and you can even see the lights dimming a bit when that happens.

It's been raining a lot these past few days and I haven't had a chance to troubleshoot, but I plan working on your suggestions hopefully tomorrow.
 
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Old 03-18-05, 02:20 PM
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Wink

Go to EM or AUX heat for now dont let the compressor try and come on like that. Could be a capacitor bad in the outside unit there.

ED
 
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Old 03-19-05, 09:30 AM
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Check what you can when you get a chance. From your last response I would say don't run it like that because you'll beat it to death. Sounds like a hard start kit or just a new capacitor is in your future. It may be a permanent fix or it may just buy you some time till replacement time.
 
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Old 03-22-05, 07:46 PM
oanglade
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The humming is not coming from the compressor. It's coming from the service panel area from either the capacitor there or the transformer that is part of the contactor (at least it looks like a transformer). The contactor "pushes" in when the unit starts.

The capacitor has 2 contacts with 2 wires on each contact.

The unit is a Tempstar modem CH5036VKB3

Is there a way to test the capacitor? Does it make sense that it could be the cap, even though the fan starts (but not the compressor).
The compressor did feel a little bit warm. Not hot.

Running on Emergency for now.

Are there any links to diagrams of the relays, delay board, etc so that I could figure out how to and if it is possible, to bypass each component until I find the guilty one?

On that panel I see (going from memory) the capacitor, the contactor, a short cycle timer and a defrost circuit board.
 
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Old 03-23-05, 05:13 AM
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The time delay could be bad. Just a matter of jumping it out and trying to start it again. One way to chacke a cap is with a multimeter if you have one, but if you by-pass the time delay and it still don't start a new cap is usually under $10 bucks.

Did you ohm out the compressor yet?
 
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Old 03-24-05, 07:36 AM
oanglade
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Doh! I forgot to do that yesterday! I'll get to it tonight.

Anyway, I took a good look at it yesterday. I found the diagrams from the heat pump manuals.

The cap is a three connector one and it seems that it also supplies the fan, which works fine. I bypassed the time delay relay and it didn't make a difference.

All the other devices inside the access panel would cut off the fan if they were not working, from what I can see in the diagram, so I don't think it's any of those.

I know it's not a high voltage problem because the same lines supply the fan and it works (unless the cap is good enough to start the fan, but not the compressor). So it leaves me with the 24VAC lines and the path that goes through the compressor only has the time delay, which I already bypassed, and the high pressure switch, which is not tripped.

So, to me, it's starting to look like either there is no regrigerant or the compressor itself is bad. I'll ohm it out tonight, but more and more I'm leaning towards going ahead and calling for service/repair. I am enjoying the learning process, even though I really haven't had much time at all to work on this.

Come to think of it, we did notice at the start of the cold season that the "auxiliary" light on the thermostat was coming on more often this season than last year.

Thanks for all the advice. I'll post after ohming out the compressor.
 
  #14  
Old 03-24-05, 03:47 PM
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Did you check to see that you are getting 240 from the contactor to the compressor? If you are getting power to the compressor, then it may of tripped out on over load.
 
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