Heat pump locked up, call tech or not?

Not necessarely, got make/model/serial number??

Maybe it went into a defrost cycle?? Got outside temps and humidity??

It may or may not be a problem. Nobody can tell for sure without the laying on of hands.

My crystal ball is kind of cloudy, you need to call your local tech. The "average" tech probably won't be able to figure it out, but a *competent*, licensed, insured, professionally trained one will.

Trane residential 3 ton heat pump. 33 F and light rain. Also a screeching noise a few minutes earlier when I was "walking" the dog, causing me to go look and notice it was humming but not spinning. I've never seen it defrost.

That's my fear, most companies have one sharp guy and several wannabes, you never know which one will show up. But an intermittent problem can puzzle even the pros. Repair is a lot easier than diagnosis.

Trane residential 3 ton heat pump. 33 F and light rain. Also a screeching noise a few minutes earlier when I was "walking" the dog, causing me to go look and notice it was humming but not spinning. I've never seen it defrost.

That's my fear, most companies have one sharp guy and several wannabes, you never know which one will show up. But an intermittent problem can puzzle even the pros. Repair is a lot easier than diagnosis.

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Screeching noise?? continuous screeching?? or more like a "sneeze"?? Filter(s) clean?? all the vents wide open??

You didn't say how old the system is...

Ah, right. New system, previous owner put it in as a selling point but never used it, we've been in the house a year.

There've been no problems with the outdoor unit, and I've been surprised by how cold it can get without bringing on the strip heaters. Heat pumps have made a lot of progress since I last had one (I've been overseas several years, no AC needed.)

The house temperature (on the thermostat) was down to 64 this morning, but it came back to 70 and has maintained that.

The attic airhandler on the other hand has burned out two fan motors in a year, both under warranty. I haven't touched the vents but can't swear this motor is pushing the same amount of air as the last one. You're thinking low air flow across the coil?

The screeching noise happened when I was ensuring the dog was properly toileted and couldn't interrupt to go look. I'd guess maybe 1-2 minutes, somewhat like an alternator belt slipping on a car but metallic sounding. I didn't identify it as the compressor right away because I've not heard one make a noise like that.

Ah, right. New system, previous owner put it in as a selling point but never used it, we've been in the house a year.

There've been no problems with the outdoor unit, and I've been surprised by how cold it can get without bringing on the strip heaters. Heat pumps have made a lot of progress since I last had one (I've been overseas several years, no AC needed.)

The house temperature (on the thermostat) was down to 64 this morning, but it came back to 70 and has maintained that.

The attic airhandler on the other hand has burned out two fan motors in a year, both under warranty. I haven't touched the vents but can't swear this motor is pushing the same amount of air as the last one. You're thinking low air flow across the coil?

The screeching noise happened when I was ensuring the dog was properly toileted and couldn't interrupt to go look. I'd guess maybe 1-2 minutes, somewhat like an alternator belt slipping on a car but metallic sounding. I didn't identify it as the compressor right away because I've not heard one make a noise like that.

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Could be any of a couple of different things... Best thing is to get your local tech out to take a look at it.

Well, no, not necessarily. If it's in a condition where the problem is not likely to be correctly diagnosed, then bringing the local tech out to look at it is probably the worst thing.

That's why I asked. Problems that cause a compressor to lock up but then hours later work fine might be easy to diagnose or impossible. I'm leaning toward impossible right now, can anyone suggest an easily diagnosable cause?

Low on freon, for one.

Hah! You got me, I didn't see that coming. In theory, it should be possible to easily diagnose low freon by measuring superheat or subcooling, right?

I've never seen that done. The techs where I work (I'm not in that section but I see them sometimes) will weigh a charge if they're being careful.

The compressor relies on the flow of cooled gas through it for internal cooling. Without that, it can overheat over time and go off on internal thermal safety.

Yes.

That's one way.

Put some tattle tale devices on it. You area service company should have them available.

Most three year old girls aren't allowed out after 7 Pm.

It's always low freon, or replace thermostat. I've weighed in charge, that's fairly routine work. Also by superheat. Not done the subcooling one, yet.

And that you know, Stormy, by stalking them?

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"Not done the subcooling one, yet."

Hahahaha! HAHAHAHA! BWAHAhahahahahahaahah!

CHECK YOUR START COMPONANTS

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Actually, I have a new theory. I think it is possible that it was defrosting and I caught it at the end or beginning of a cycle and misinterpreted it as failure to start. I didn't see any frost on it, but if the defrost cycle is sensing temperature or on a timer maybe that could do it.

It has worked fine since then - maybe it healed on its own!

IT'S A MIRACLE !!!!!

PRAISE WILLIS ! PRAISE WILLIS !

Actually we all held hands while standing in a pentagram and removed the evil curse on it. Please submit $2,500 plus tips for our endeavors.