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-   -   heatpump - no heat (http://www.diychatroom.com/f17/heatpump-no-heat-167034/)

wetbar 12-20-2012 09:51 PM

heatpump - no heat
 
Hey, I have a heat pump that I am having a problem with. I got a call last week and added R-22. Got another call last night for no heat, and electric popping breaker. So I did fix 3 leaks and pulled a vac broke with nitrogen on high, repulled and broke on low side and pulled again. added the factory charge(6 pounds) and these are the number I got:


outside temp is 50 dry bulb and raining

Vapor 125 PSi and 77 degree
Liquid 110 psi and 67 degree

So I am thinking comp is bad right? only 15psi dif high-low

So I checked true suction and it was 51 psi.

I am at a lost at this point! I check the filters, coil,fan all are ok.

Any clues what to check next?

Thanks

beenthere 12-21-2012 04:29 AM

Did you change out the liquid line filter drier? Could be restricted, or the metering device.

beenthere 12-21-2012 04:29 AM

Did you change out the liquid line filter drier? Could be restricted, or the metering device.

wetbar 12-21-2012 07:18 AM

I thought maybe the same thing, so i took out the filter dryer and back seated both lines and blew nitrogen from 1 side to the other at about 300 psi for a good 5 minutes. I would think that would clear any restriction that I had. I didn't think to check the meeting device in the outside unit. it is a piston. if it was clogged it would cause low suction pressure. I will check that today, any thing else you can think of that I didn't check?

thanks for the help

beenthere 12-21-2012 12:10 PM

Not at the moment.

wetbar 12-21-2012 09:37 PM

OK I went back out and checked the piston and everything was fine. put it all back together did another triple vac and got the same results. Had one question though, I was looking at the charging chart and notice that it called for a txv on the inside unit. The inside unit has a piston as well, that would not matter right? It is a metering device, and this was working, and it heat mode the metering device is bypassed anyway. Im just lost what to check next. . . It sure is looking more and more like a bad comp to me. I was thinking maybe a stuck reversing valve? I did switch it 9 or 10 times and seemed to be working fine. Vapor line dropped liquid line went high (when I shut the fan off). reverse it back to heat and the numers went back to 15-25 PSI apart. Any clues?

beenthere 12-22-2012 04:14 AM

If the liquid line pressure can increase in cooling mode and the vapor pressure drops, Its not the compressor. It could be the RV isn't moving all the way over in heat mode though.

Marty S. 12-22-2012 08:23 AM

There shouldn't be much pressure difference between the liquid line and discharge line wetbar. In heating mode you check pressures at liquid line and true suction. Superheat ,subcool and BTU output will tell you more what's going on.

When a heat pump runs low on charge the bottom few rows of copper do not defrost. As the ice gets thicker it crushes the tube and causes what's known as baby butt. Look for loose fins along the bottom rows and any evidence of crushed copper.

wetbar 12-22-2012 11:39 AM

I am stuck on RV, I thought it was that yesterday, but it appeared to switch to ac mode. Like I said I didn't get the head up to high because it was only 38 degrees. but the low side started dropping right away. How do I check the RV without replacing it? I will tap on it a little to see if the number change, but other than that any clues?

Once again thanks for all the help!

wetbar 12-22-2012 01:04 PM

Ok here are the numbers and pressures when I got here today. true suction is 56 p s I and 40.1 degrees. giving me a super heat of about 11 degrees. The liquid line is 125 and 67.2 degrees. giving me about 3 degrees subcool. The vapor line is 145 psi and 83 degrees.

Marty S. 12-22-2012 04:17 PM

Looks under charged from here unless it was 40 something inside the house. Remember the function of the coils is backwards in heating so the indoor coil and house temp gives head pressure,suction is outdoor. Even with a fixed orifice your subcool should be higher in heating mode. Add another half pound and see what she does.

I hardly ever see reversing valve problems unless they crack. Only twice have seen them stick and in both cases the suction pressure was crazy high with slightly low head. Your suction isn't high so I don't think it's a RV problem.

beenthere 12-22-2012 05:36 PM

Yep, may be a bit under charged. If you have a good clamp probe. Clamp it on the compressor discharge line about 6 inches from the compressor. That discharge temp should be around 126 warmer then the outdoor temp in heat mode. If its more ad some gas.

wetbar 12-22-2012 10:00 PM

I ended up adding another 2 pounds above factory charge. The pressures didn't change but the temps did. The super heat went to darn near 0. I ended up replacing the outside unit charge to factor charge and works like a champ. I'm going to tear down the old unit next week on the bench and see what's up with that. I will let y'all know.

Thanks for that help.


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