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SnooMc · 10-02-2019, 02:43 PM

So, we're here in SD, where the days and nights are currently trending chilly (it's supposed to be 29 tonight). The heat pump is keeping us warm so far. However, although we understand how a heat pump works, there is a sound that we are curious about.

During less cold times, the cycle is: compressor comes on for a minute or two with maybe some clicking/gurgling sounds, then the fan comes on until temp is reached, then the compressor and fan turn off.

During colder times, as at night, the system runs almost continuously and the cycle is: compressor is on with the clicking/gurgling sounds, then the fan runs until temp reached (presumably), then the fan turns off but the compressor keeps running with clicking/gurgling - then !!!!WHOOSH!!!! after which, the fan comes on normally, repeat all night. It's this WHOOSH that we're curious about. It scares the cat.

**DKB_SATX** · 10-02-2019, 02:50 PM

This sounds like something that's normal for any air-sourced heat pump, even residential ones. If the heat pump thinks the external coils are starting to freeze up, it'll let hot working fluid flow through them for a bit to defrost the coils. It makes a whooshing sound.

GMFL · 10-02-2019, 03:09 PM

Yep, perfectly normal.

SnooMc · 10-02-2019, 03:26 PM

Okay, thanks. I'm guessing I've never heard it before because house heat pumps are removed from the living areas a little farther

uraljohn · 10-02-2019, 04:37 PM

Heat pumps are only good down to around 35 degrees. Anything under that temp you probably should use your gas furnace. If the heat pump is running continuously it is unable to supply the demand placed on it. That will cause "Freeze up" and you will get your sound as it struggles to provide.

Our home has a heat pump with a high efficiency gas furnace backup. The installer set it up so that below 40 degrees the gas furnace steps in to help the heat pump down to as low as 35 degrees. Below 35 degrees it is gas furnace only. Hope this helps you some. Happy travels.

uncle_bob · 10-02-2019, 05:40 PM

Hi

Our heat pumps make that same noise in Montana, Wyoming, North Dakota, and Colorado. So it's not specific to South Dakota

Indeed it is a very typical part of the operating cycle of the heat pump.

Surprisingly enough we have had good luck with ours right down to near freezing. No long run times. No nonsense stall outs. No error messages. Since they run on campground shore power and the backup needs propane, I'll run them as long as they don't seem to be in trouble.

Bob

James o · 10-02-2019, 05:57 PM

That noise is reversing valve changing direction of refrigerant .Some systems are
In cooling mode without power to reversing valve.
So when unit starts it powers valve open to reverse charge
For heat.

SnooMc · 10-02-2019, 07:32 PM

It's supplying plenty of heat, so far. We might use the furnace tonight though. I can't imagine it's reversing the flow every time...it's in Heat Pump mode, and it whooshes only when running through the night, never when coming on intermittently. It's almost like it's clearing its throat before busting out some more tunes....

James o · 10-02-2019, 07:48 PM

Hi
Then it is reversing to thaw out coil if it starts to freeze
Which it will in low temps.

Jim AC contractor

SnooMc · 10-02-2019, 08:29 PM

Ah, my husband wondered if that was it!

**jcanavera** · 10-02-2019, 08:45 PM

What is happening is the heat pump (at least on mine) when you have extended run times will shut the fan down and reverse the flow of the refrigerant that’s the noise you hear. Keep in mind when in heat pump mode, the outside coils can get cold and condense moisture on them. If that moisture freezes you get ice and and no air flow. That translates to no heat. That reversal of the refrigerant with no fan, heats up that outer coil to defrost any ice. When my trailer was new I was camping in a cold rain. Lots of run time and not enough defrost time. Outside coils froze up. We were out of the trailer and upon arrival I had a cold trailer. Here’s a picture.

I’m not sure if the newer ac units have sensors or still use run time like mine does. I know my dealer didn’t tell me how the heat pump operated and the first time it went into defrost mode I thought the fan motor had failed.

Jack

uncle_bob · 10-03-2019, 09:17 AM

Hi

Based on what I've observed, there seems to be a sensor in ours that fires up the "defrost cycle". It does not appear to be related to run time.

Bob

ChuckZ · 10-03-2019, 09:45 AM

I've gotten the Whoosh also but mine has been accompanied by a discharge of water into the cabin below the unit. My drains are fine for the AC. It has only happened with the HP. Thoughts?

**jcanavera** · 10-03-2019, 02:07 PM

Quote:

Originally Posted by ChuckZ

I've gotten the Whoosh also but mine has been accompanied by a discharge of water into the cabin below the unit. My drains are fine for the AC. It has only happened with the HP. Thoughts?

Seems strange since summer is when the water condenses on the inside coil. When in heat pump mode that coil gets hot/warm so moisture shouldn’t condense there. Wonder if that outside coil and the water it condenses is finding a path inside?

Jack

SnooMc · 10-03-2019, 10:42 PM

We made it through last night without issue, just running the heat pumps, no issues. Tomorrow, however, I'm checking everything for leaks.

uncle_bob · 10-04-2019, 06:58 AM

Quote:

Originally Posted by ChuckZ

I've gotten the Whoosh also but mine has been accompanied by a discharge of water into the cabin below the unit. My drains are fine for the AC. It has only happened with the HP. Thoughts?

Hi

If a chunk of ice actually falls off the unit, it can block a drain. Fall is also the time you are more likely to get leaves falling off trees blocking things.

Bob

ChuckZ · 10-04-2019, 07:09 AM

Quote:

Originally Posted by jcanavera

Seems strange since summer is when the water condenses on the inside coil. When in heat pump mode that coil gets hot/warm so moisture shouldn’t condense there. Wonder if that outside coil and the water it condenses is finding a path inside?

Jack

Thanks for the info.

Actually, it was last February when we experienced the "dump". I haven't run the HP since then. We won't be using the HP again until next February and we'll see then.

**jcanavera** · 10-04-2019, 08:34 AM

Quote:

Originally Posted by ChuckZ

Thanks for the info.

Actually, it was last February when we experienced the "dump". I haven't run the HP since then. We won't be using the HP again until next February and we'll see then.

Yeah, Bob did give you a good piece of advice in that the area in the outer part of the box has to drain also and unlike the inner coil box, it can get debris in it. That drain for that area is somewhat protected but if it gets clogged then that frozen condensate from heat pump operation could have it's drain clogged. You may have to go up and pull the shroud.

Note while I can't comment on your model air conditioner/heat pump, mine had foam baffles in it that directed air flow, and pulling the shroud has to be done carefully to not tear those baffles. I didn't know that until I had to replace my shroud which had cracked due to UV exposure. The new shroud came with a fresh set of foam baffles to replace those which tore when I pulled the shroud open.

Jack