Help Heatpump freezing

Started by tilhasbb, October 24, 2013, 10:07:33 AM

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tilhasbb

Hello,

I have a Lennox HP19 system that is around 15 years old. The compressor died 5 years ago and it was replaced.
Last year this same issue started happening at the end of winter and we never fixed it. In summer it cools perfectly and uses minimal electricity. I've washed, cleaned everything and replaced the filters. First day of winter it worked perfectly (first time I switch it from cooling to heating). Today it froze again...
I have two questions.
1) Is it worth repairing or buying a new system? since it is old.
2) What could the problem be?

Thank you in-advance
You can find the full resolution photos here
https://www.dropbox.com/sh/nbt4z0m9t23smq6/kCpbLT5hQ9

Admin

At 15 years it's a good time to consider replacing it.  Is your filter clean?

tilhasbb

Yes it's clean. I'm running the fan on now to defrost it then I'll run without the air filter...

tilhasbb

So I waited about 5hrs for everything to melt. I turned off power from the main circuit break to everything.

I turned it back on now and i only put the thermostat a few degrees more than the ambient temperature to be sure its only heat not emergency heat. It works perfectly now... I got an infrared thermometer. Ambient is 16C (61F) , thinner hose is 24C (75F) and wider hose is 60C (140F).
I also checked the 3 way valve outside and 2 were cool (outside coil and compressor side) and the one going into the house very hot.

rmuntz

It appears from the pictures that it was the inside coil that froze, in the heating mode the indoor coil should be the hot coil. It's possible that the reversing valve was stuck in the cooling position, generally with heat pumps if you have to change a burned out compressor it is a good idea to replace the RV at the same time.
Just a thought.

tilhasbb

Here is a picture of it melted.

I hit the test button (red arrow) and it seems to be working again...

Admin

Download the Lennox HP19 Service Manual - Here

Follow pages 5 and 6 to test the defrost mode.  The "test button" you have been pushing is the contactor, at least that's what your red arrow is pointing to in the above picture.

When the defrost mode ends, the reversing valve should switch back to the heating mode.  The reversing valve should only be energized in the cooling or defrost mode.

What Rmuntz said!!   ;D

tilhasbb

Thank you for the manual!

I tried to do the test yesterday and I can't figure this out.
I turned the power off on the system. I put a jumper on the test pins. Turned on the power to the system and turned on Heat and increased the thermostat temperature to insure the system goes on. Went outside and nothing... it wouldn't turn on. I removed the jumper from the two test pins and that didn't help... after searching I find a red button, i push it and the system is running again. What happened?


Admin

That's the high pressure switch.

From what you're saying everything seems to work fine until the system enters it's defrost mode.  Either the defrost board is bad or the reversing valve is sticking, in either case you're stuck in the cooling mode.

Try testing the defrost mode again now that the high pressure switch has been reset.

tilhasbb

Ever since I have switched the defrost timer from 60min to 90min it has not frozen... It has not been cold yet but I'd rather not touch it.
Maybe it is not staying on for over 90 minutes to warm up the house so it's never going into the defrost cycle. Tonight and tomorrow night it will be very cold and the system will work hard. I don't want to touch it before letting it work.

I'll keep you posted.