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Old 10-24-2013, 10:11 AM   #1
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Help Heatpump freezing


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
Attached Thumbnails
Help Heatpump freezing-photo-2013-10-24-10-17-48-am.jpg   Help Heatpump freezing-photo-2013-10-24-10-25-19-am.jpg   Help Heatpump freezing-photo-2013-10-24-10-25-00-am.jpg   Help Heatpump freezing-photo-2013-10-24-10-25-09-am.jpg  

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Old 10-24-2013, 10:42 AM   #2
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Help Heatpump freezing


It is a 1994 unit from the serial #. Come back this evening as we have a couple heat pump Pros and one that does a lot of Lennox. There is a defrost initiation control/sensor that may be faulty. Not going into defrost. Probably worth fixing unless it is losing Freon.

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Old 10-24-2013, 10:47 AM   #3
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Help Heatpump freezing


Thank you. Just checked and your right I think this was installed when they built the house in 1995.
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Old 10-24-2013, 10:53 AM   #4
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Help Heatpump freezing


From the serial number its 19 years old.

Wouldn't have recommended a compressor 5 years ago.

Was it in cooling or heating when it iced up?
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Old 10-24-2013, 10:58 AM   #5
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It freezes up when it's in heating mode.
first 2 days I ran the system in heating it worked like a charm. I was getting 50C (122F) till the house warmed up. That's why I'm confused.

Last edited by tilhasbb; 10-24-2013 at 11:02 AM.
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Old 10-24-2013, 11:00 AM   #6
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Help Heatpump freezing


Yuri is right it could be the defrost sensor or it can be the defrost board. Need to run a few test.
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Old 10-24-2013, 11:08 AM   #7
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How do I run these tests?
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Old 10-24-2013, 11:23 AM   #8
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Remove the panel on the side of unit, locate the circuit board ,on the board should be two test pin to manual put the unit into a defrost state. If the unit will not go in to defrost state the board is bad and needs replaced. Also, check and locate the defrost temperature sensor which need to check by resistance test to temp.
What a video on how to manual put two test pin into defrost, before you try.
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Old 10-24-2013, 11:26 AM   #9
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The cheapest way to go as Yuri said , I would change the sensor first and see what happen
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Old 10-24-2013, 11:51 AM   #10
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Quote:
Originally Posted by ryandeen View Post
The cheapest way to go as Yuri said , I would change the sensor first and see what happen
Looking at the indoor evap....does anything look highly peculiar.

Start changing parts and start with the cheapest one...good advice

Last edited by Technow; 10-24-2013 at 12:08 PM.
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Old 10-24-2013, 12:01 PM   #11
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Help Heatpump freezing


Quote:
Originally Posted by Technow View Post
Looking at the indoor evap....does anything look highly preculiar.

Start changing parts and start with the cheapest one...good advice
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.


As for testing it. Here is a picture of the board. There is a test pin on the bottom right and a resistance area. But I don't see the temperature sensor to check the resistance, or is that the resistance?

Also the T1 T2 T3 30/60/90. It's currently set to 60. Can I set it to 30?


Note in the second picture. the two on the right were FROZEN and the left (coils outside) was not frozen.
Now the two left are cool and the one on the right is hot....
I'm thinking now it is circuit board or sensors. Time for me to test!
Attached Thumbnails
Help Heatpump freezing-photo-2013-10-24-12-29-55-pm.jpg   Help Heatpump freezing-after-heating.jpg  

Last edited by tilhasbb; 10-24-2013 at 12:06 PM.
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Old 10-24-2013, 02:57 PM   #12
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Help Heatpump freezing


Ice on the indoor coil of a heat pump means it wasn't in heat mode. May have been in defrost, and the defrost timer and defrost thermostat are bad. It could also be that the thermostat is not sending voltage to the O terminal of the defrost board. Best to check it with a multimeter, instead of buying a board you don't need.

Was a new thermostat installed this year.
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Old 10-24-2013, 03:56 PM   #13
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Here is a link to some info that may of use:

http://www.completeheating.ca/manuals/LennoxHP19.pdf

Pages 4-6 explain how to test the defrost cycle and change the timer.
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Old 10-25-2013, 09:49 AM   #14
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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?
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Old 10-25-2013, 10:00 AM   #15
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According to the schematic that is the high pressure switch.

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