Help Heat Pump Freezing

[JohnR]

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 https://www.dropbox.com/sh/nbt4z0m9t23smq6/kCpbLT5hQ9

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[Jim Katen]

That heat pump is 19 years old.

Frost on an indoor coil in the heating mode is a new one for me. It makes no sense. Perhaps your reversing valve is stuck.

Any repair that will involve removing the refrigerant will not be cost effective because the cost of new refrigerant is so high. (We're seeing costs of about $100 per pound, installed.)

[JohnR]

Thank you.

What bothers me is that it ran for the first 2 days I switched the system to heating. I was getting 50C (122F) till the house warmed up.

So it could be the reversing valve getting stuck but how come it worked for a few days before... hmmm

Ill start getting quotes on new systems...

[Bill Kibbel]

Reversing valve stuck or solenoid failed.

The reason you got 122F is the back-up heating was functioning. Then, enough ice formed on the evap. coil to block air flow.

Your HP was manufactured in '94 and compressor in '05. It's probably not worth putting any more $ into this system. The high efficiency heat pump systems available now are much less costly to operate than a near 20 year old Lennox.

[John Kogel]

Bill and Jim are correct. The heat pump is still working as an air conditioner, pumping cold in. The backup heat system is trying to heat the place. Cut power to the outdoor unit until help arrives. There should be a disconnect out there.

That ice will turn to water, so make sure your condensate pan and drain are clear.

[JohnR]

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.

I think it's just the defrost board. I could get the entire kit for 200$ and replace it my self... but I need to figure out if that is the problem.

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[Jim Katen]

If it's getting stuck in a defrost cycle, that would do it.

For $200, it might be worth just changing out the board. If it works, great. If it doesn't work, you can return the board.

[Marc]

The inside coil is the condenser when on heat mode. Defrost is for the evaporator which, in heat mode, is the outside coil.

I'm with Bill. Solenoid valve. When the refrigerant becomes contaminated, it manifests as a malfunctioning solenoid valve right quick. Had one myself long ago.

I'm not saying the valve is bad, I'm saying the refrigerant gas/oil is contaminated and interfering with the functioning of the valve. When combined with the age of the system and R-22, it's a good excuse to replace the whole kit and kaboodle.

Marc

[JohnR]

I'm going to check if there is a 24V on the solenoid when defrost mode is on. If there is 24V that means the board is working and the solenoid is stuck? So I'll try unplugging and replugging the 24V and hear if it moves? if not i'll help it with a wooden stick and hear if it moves.

Right?

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[Marc]

I'm going to check if there is a 24V on the solenoid when defrost mode is on. If there is 24V that means the board is working and the solenoid is stuck? So I'll try unplugging and replugging the 24V and hear if it moves? if not i'll help it with a wooden stick and hear if it moves.

Right?

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Some valves are in cool mode without voltage and others are in heat heat without voltage. What's important is that the voltage reliably drop in or drop out when you switch the thermo between heat and cool - with the thermo calling for the outside unit to function.

That was thoughtful though. A defect involving the thermo or the 24 volt wiring could cause the same symptoms as an unreliable solenoid valve.

Marc

[Bill Kibbel]

If you put a jumper on the 2 pins below the word TEST, it should rapidly cycle through the defrost mode. You'll hear a load whoosh at the start of the defrost cycle and a similar whoosh at the end.

Use two alligator clips at each end of a wire.