We had a heat pump installed a couple of years ago, which saved us quite a bit on gas bills. Last fall we noticed that when the compressor kicked in for auxiliary heat, it made quite a bit of racket. Called the installer and they came out to check it out. He adjusted a setting on the electronic thermostat and went away. Now, some months later, it’s making a LOT of noise, and it seems like it’s constantly calling for ‘auxiliary heat’, and our gas bill has shot up. Exterior temperatures in the morning are generally in the 40s. I’m going to call them back again tomorrow to investigate this, but I’d like to hear any thoughts on this from qualified Dopers.
Turn the heat pump off until the tech gets there.
Simply turn the stat to emergency heat. You may be damaging the unit to let it run.
Is the noise coming from the inside or outside?
Inside or outside of what? The compressor sits outside, of course. When a service guy was here in the late fall, I asked him about the noise. He said it’s normal when the compressor is in defrost. But it shouldn’t do this when it turns on, IMO. I’m calling them tomorrow and it’s still under warranty.
Well if the noise is coming from outside…
First of all, I guess, is the compressor doesn’t kick in for auxiliary heat. Auxiliary heat is a series of electric heat strips (like a big toaster) in your air handler. They are silent, whether they are working correctly or not, and the devices that control them (called “sequencers”) are silent as well, and that too is whether they are working or not.
It’s hard for me to interpret “Buh-WANGGGG”, but I can give you a laundry list of possible causes:
1) The unit is overcharged.
Your compressor is a vapor pump, and if the unit is overcharged it may run liquid refrigerant through the compressor. That noise is typically a jarring vibration; an extra-strength shuddering. It will, in time, destroy the compressor.
2) The unit is undercharged.
A unit that is undercharged will ice up on the outside—a lot. But its also icing up on the inside too. I’ve seen unit with so much on the inside that the fan blades on the HP outside were hitting the ice build up. Common? No. But not entirely uncommon either.
3) Bad defrost control
A unit that isn’t defrosting can cause the conditions above; both that of running liquid refrigerant through the unit, and severe ice build up on the inside of the unit.
4) A fan blade that’s out of balance, or the motor is going bad.
Any fan needs a set of blades that are balanced. if the fan is out of balance it will make noise. Here too, however, it is usually manifested in shaking and vibration, not a “Buh-WANGGGG.”
5) Some obstruction in the area of the fan and/fan blades.
Is the unit level? Any body run into it with the Cub Cadet? Look inside when it’s running. Does it shake or vibrate?
Keep in mind that there are only 2 components outside that will make noise, the compressor and the fan/motor. IME, it is the compressor that is the likely culprit.
The root cause can be electrical or mechanical. Most often------from what you’re describing---- its mechanical.
In any event, I can’t imagine what a technician could do to the thermostat to affect any change in the last visit. (and, fwiw, I’m a technician)
We don’t have much information to make a more informed internet diagnosis (which would be very difficult in the best circumstance) but I’d be leaning towards the refrigerant charge, or some obstruction in the fan blade area.
Thats my SWAG and I’m sticking to it.
No, it should not make that noise when in defrost. When the unit goes into----and goes out of-----defrost there is a discernible “Whoosh!” noise. That’s natural and OK.
Buh-WANGGGG is not OK.
Have him verify that the crankcase heater is working correctly. Liquid refrigerant will migrate to the coldest place when the unit is off. A crankcase heater prevents it from migrating to the compressor when the unit is off.
It is a Very Bad Thing to have liquid in the compressor when it starts up. If the noise happens only when the unit starts up, that suggests that the compressor is seeing liquid.
Thanks. I’d just like some ammunition when the guy shows up. I went to AC & refrigeration training in the Navy, but that was 30 years ago.
The noise sounds like the compressor is under considerable load, sort of a buzzing, vibrating noise that come on loud, then sort of fades, then comes back loud again before stopping. It’s very loud and I’m sure is driving the neighbors nutso.
Boy o’ boy that sounds like an overcharged unit.
Compressors are very stout machines and will take a lot of abuse before they die. But die they will. And they last long enough that the repair will be after your warranty runs out. I’m not joking.
A heat pump is best charged under summer conditions. It can be done in winter but the only professional way to do that now is to:
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Recover the refrigerant
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Pull the unit into a <500 micron vacuum
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Weigh the charge in.
Turn the unit off for now. If its overcharged it can scramble at any time.
A final thought…
The path of least resistance is to take out enough refrigerant to stop running liquid through it. (keep in mind, this is assuming that that’s the real problem)
But that’s not the correct way. The correct way—given that its winter----is to weigh in the charge.
Many techs/companies are going to be loathe to do that now because it is time consuming and they’re not getting paid. But if they didn’t set the charge correctly the first time, they wont want to now.
If it’s the charge they probably wont be entirely forthcoming and/or speak in jargon or obfuscate. If you determine its the charge, insist the charge be removed, a vacuum pulled and a new charge weighed in.
Tech came, did a lot of tests, checked amperage, suction/discharge, adjusted some of the settings. Basically, the thing makes noise on defrost cycle, but the changed settings should help with frequency of occurrences. He says if the noise becomes excessive again, he’ll bring the Carrier rep out to have a look/listen.
I found your problem. 
Seriously, I can’t think of any reason it should make noise in the defrost cycle. Raindog may correct me but defrost is basically the cooling cycle without the outdoor fan. Except overcharge, but I’d expect that to be obvious even in the heating cycle.
You’re spot on.
Defrost is a necessary evil, but an evil nonetheless.
Defrost is putting your system into air conditioning in the middle of winter.
Two things are done to expedite/ mitigate this fact:
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The outdoor fan is turned off to speed up the ice melting process.
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The indoor supplemental heat is energized to neutralize/ mitigate the fact you’re air conditioning the place.
In any event, it shouldn’t be making any more noise than the dead of summer. thats what has me a little confused about what the tech said. Defrost is not inherently noisy…with the exception of when it goes into, and *leaves defrost *mode.
There is semi-loud “whooshing” noise from the reversing valve. other then that, it should not be noisy.
It’s apparently normal for Carrier. I asked him about vibration isolators and he said that there are rubber grommets/washers under the compressor. They may be inadequate to dampen the vibration, IMO. Anyway, it’s quieter now and hopefully will stay that way.
By the way, the noise started last summer, as I recall.