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Old 11-19-2015, 12:04 AM   #1
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heat pump turns on for a few seconds then off. Aux heat not warming house


I have a 3 ton American Standard Heat Pump on a dual zoen system that heats my basement (zone1 and main level zone 2) it has been working fine for the last 5 years. I think it is about 7 years old, but wasn't used for the first two years.

The thermostat is centrally located and there is no heat source near it. When I turn on the heat, the compressor fan kicks on for about 8 secs out side then shuts off.

The thermostat will eventually say auxilary heat, which does little to keep the 3000 sq ft home warm in Charlotte, NC area.

Any ideas where to trouble shoot first?

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Old 11-19-2015, 01:26 AM   #2
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heat pump turns on for a few seconds then off. Aux heat not warming house


Does the indoor fan motor stay on when this happens?

The aux heat should be able to heat the house on it's own.

Could think of a few things that will cause this.

If I was in your position, I would check for voltage to the outdoor unit (24v between C and Y on the defrost board)

If you're getting a consistent call for heating operation at the outdoor unit yet it's shutting off, the problem is in the unit itself. A safety in the outdoor unit may be cutting it off; some fancier defrost boards may have a diagnostic led that tells you what's wrong.

Otherwise it's in the control circuit upstream; you would have to work back there - maybe in the zoning controller.

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Old 11-19-2015, 05:38 AM   #3
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heat pump turns on for a few seconds then off. Aux heat not warming house


Sounds like the compressor may be shutting down due to a low pressure switch doing its job.

You may not have enough aux heat to keep your house warm.
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Old 11-19-2015, 06:34 AM   #4
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heat pump turns on for a few seconds then off. Aux heat not warming house


I would guess BT is right on the HP. You have enough overall pressure in the system so the low pressure cut is not effected on start up but as soon as you're in operation the low side drops below the cutoff point.

You don't mention the size of your back up heat and if it is staged. I'm assuming it's electric? It's either undersized or you have a missing stage (bad relay, over temp cutout or element)
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Old 11-19-2015, 08:54 AM   #5
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heat pump turns on for a few seconds then off. Aux heat not warming house


Yes the indoor blower fan stays on but just blows air.
is this defrost circuit board typically inside the outside compressor?
anyone got a photo of one so I know what I am looking for. As far as I can tell the electronics are located underneath your typicaly corner sheet metal cover.

I am not sure the size of the electrical heating elements.
I thing years ago I set up the zoning system to prevent people from accidently using the electrical heaters after someone used them accidently and got a $400 heating bill in January.

lastly lets say it is a low pressure swtich cutting off, if that is the diagnosisi what is the solution/cause of this? low freon?

thanks for all the help!
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Old 11-19-2015, 09:05 AM   #6
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heat pump turns on for a few seconds then off. Aux heat not warming house


Freon leak. Leak in indoor or outdoor coil or elsewhere. Coil leaks seem to be the most common. Accumulator rusting and leaking also happens.

Solution. Buy a electronic leak detector and find the leak. Need gauges and nitrogen and some freon to do so.
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Old 11-19-2015, 02:30 PM   #7
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heat pump turns on for a few seconds then off. Aux heat not warming house


you can't buy the "freon" anyhow; if there's a leak someone will have to be called to fix it. need a recovery machine too, and it's illegal to work on your own system
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Old 11-19-2015, 04:44 PM   #8
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heat pump turns on for a few seconds then off. Aux heat not warming house


Quote:
Originally Posted by user_12345a View Post
and it's illegal to work on your own system

You mean I gotta pay someone else to work on my own A/C? LOL

In the USA, its not illegal for a home owner to work on the refrigerant side of their own R410A system. No EPA cert required for it here. no if its R22, that is another story.
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Old 11-19-2015, 11:38 PM   #9
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heat pump turns on for a few seconds then off. Aux heat not warming house


mean work with refrigerant.

r410a? maybe better for diy from an environmental perspective, but certainly more room for error, more dangerous 'cause of the higher pressures.
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Old 11-20-2015, 12:17 AM   #10
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heat pump turns on for a few seconds then off. Aux heat not warming house


I called the company that installed the system several years ago. the Tech said she thought it was a Freon leak initially as well as the pressure gauge read 20psi. After a half an hour looking for a leak, she had me switch the system to AC and she determined that the spider valve (not sure if that is the name of it, but it's the piping in the outside unit that goes from a big tube and spiders out to all the tiny tubes)
was bad.

Estimated cost is $750 for 10 lbs of refrigerant r22.
Why cant they just vacuum the system and then put the old refrigerant back into it after the faulty valve is replaced?

cost of new valve and labor probably at least $1000?

I'm wondering if I should just scrap the outdoor unit and upgrade it to r410a?
http://ingramswaterandair.com/coaire...p-p-22081.html
I can get a new unit for around $1000, and based on my searches last spring can get a local hvac company to braze in a new condenser for $500.

the tech said the indoor coil had a similar valve that would need to be changed out to r410a as well.

Last edited by aluminumwelder; 11-20-2015 at 12:19 AM.
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Old 11-20-2015, 03:24 AM   #11
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heat pump turns on for a few seconds then off. Aux heat not warming house


Quote:
Originally Posted by aluminumwelder View Post

Estimated cost is $750 for 10 lbs of refrigerant r22.
Why cant they just vacuum the system and then put the old refrigerant back into it after the faulty valve is replaced?
You can reuse the old stuff, but it's low and will need more. With R22 that will cost you. The price of it is also doing nothing but going up. A bit more time and it will be like liquid gold. I remember how high the price of r12 went when stocks began to dry up!



Quote:
the tech said the indoor coil had a similar valve that would need to be changed out to r410a as well.
It will also need to be pulled and flushed. A new coil is only another $250 or so. That maybe the better route. With heat pumps you need a good match between the condenser and coil for optimum performance anyway.
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Old 11-20-2015, 03:34 AM   #12
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heat pump turns on for a few seconds then off. Aux heat not warming house


Quote:
Originally Posted by user_12345a View Post
mean work with refrigerant.

r410a? maybe better for diy from an environmental perspective, but certainly more room for error, more dangerous 'cause of the higher pressures.
No certification required whatsoever in the USA for R410a. Anybody can buy it off the shelf.

Interestingly enough, although it's regulated in Canada and you can't buy it without certification, it is perfectly legal to import it from the USA.

It DOES do environmental damage (at least if you're a believer in global warming). It has about 1725 times the effect that CO2 does (which is why it is regulated in Canada)
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Old 11-20-2015, 04:29 AM   #13
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heat pump turns on for a few seconds then off. Aux heat not warming house


Quote:
Originally Posted by aluminumwelder View Post
I called the company that installed the system several years ago. the Tech said she thought it was a Freon leak initially as well as the pressure gauge read 20psi. After a half an hour looking for a leak, she had me switch the system to AC and she determined that the spider valve (not sure if that is the name of it, but it's the piping in the outside unit that goes from a big tube and spiders out to all the tiny tubes)
was bad.

Distributor would be the device that "spiders" out. It would also have a metering device in it. That may be bad.

Estimated cost is $750 for 10 lbs of refrigerant r22.
Why cant they just vacuum the system and then put the old refrigerant back into it after the faulty valve is replaced?

cost of new valve and labor probably at least $1000?

I'm wondering if I should just scrap the outdoor unit and upgrade it to r410a?
http://ingramswaterandair.com/coaire...p-p-22081.html
I can get a new unit for around $1000, and based on my searches last spring can get a local hvac company to braze in a new condenser for $500.

the tech said the indoor coil had a similar valve that would need to be changed out to r410a as well.
Might want to get a second opinion.
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Old 11-20-2015, 07:51 AM   #14
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heat pump turns on for a few seconds then off. Aux heat not warming house


thanks for the feedback I'm going to wait until I get a quote from her to see how much it will cost.

I'd really like to put in the geothermal system but don't think I have the $$$$ for I right now.
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Old 11-20-2015, 09:23 AM   #15
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heat pump turns on for a few seconds then off. Aux heat not warming house


Since the system is only 7 yrs old you may want to consider having them remove the existing refrigerant, make the necessary repairs and then recharge with a R22 replacement, like MO99. It would seem a waste to write off your system simply to change to 410a when there are viable replacements available for your existing equipment.

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