Reversing valve sound insulation Photograph

[sillikat]

I asked a question previously about insulating the reversing valve to reduce noise during defrost. I didn't receive any negative replies so I decided to try this. ( I have a Carrier 38YDB048 with Infinity Control)

This noise has been severe during the shift back to heating when the compressor is running in high speed, and the noise was a loud roaring sound like a heard of elephants. (the compressor is located about 3' from the kitchen window, and can be heard during "shift" at the other end of the house, about 50' away)

I placed 4" thick foam rubber on top the valve, and down both sides the outlet tubes, and then across in front of the tubes inside the Heat Pump housing.
There has been a dramatic reduction in noise , so I attached a photo to show the before and after of what I did. It has been running with this additon for about 10 days.

And, I ask again if anyone sees any harm in doing this ???

Most grateful for any thoughts . . Tom

[Mr Bill]

A'h one the enjoyment's of owning a Heat Pump. :D

[dngtig]

The only problem I could think of is the chance of the rvr solonoid coil getting to warm when energized in cooling. But I don't know if that would happen or not. Other wise it looks good. Did you get paid to make this modification or was it to please the homeowner.

[mark beiser]

Don't the Infinity heat pumps have a "quiet shift" option where it will turn the outdoor fan back on for a few seconds before shifting the reversing valve at the end of the defrost cycle?
Trane's defrost control does that and it makes a the shift MUCH quieter.

[sillikat]

This heat pump was purchased from and installed by a professional for my home, and has been driving me "BATTY" with this loud roaring sound when it switches back to heating from defrost only when the compressor is running in high speed. It is a normal acceptable "swooshing" sound when the compressor is at low speed. When it "roars", I can hear it 50' away on the other end of the house.

I purposely left the coil open on the bottom because of the possibility of overheating it.

I've covered the foam with Reflectix insulation to reduce rain water from soaking the foam. The foam is an open cell type of foam, and if this continues to work, I'll look to see if I can find a closed cell foam. (should be better to prevent water absorption)

Thanks for responding, I appreciate it . . Tom

[Gunnery Sergeant Hartman]

This heat pump was purchased from and installed by a professional for my home, and has been driving me "BATTY" with this loud roaring sound when it switches back to heating from defrost only when the compressor is running in high speed. It is a normal acceptable "swooshing" sound when the compressor is at low speed. When it "roars", I can hear it 50' away on the other end of the house.

I purposely left the coil open on the bottom because of the possibility of overheating it.

I've covered the foam with Reflectix insulation to reduce rain water from soaking the foam. The foam is an open cell type of foam, and if this continues to work, I'll look to see if I can find a closed cell foam. (should be better to prevent water absorption)

Thanks for responding, I appreciate it . . Tom

I certainly hope you don't have any problems during the warranty period.

I know if you did and I was servicing that unit, there would be a voided warranty on that piece of equipment.

[RoBoTeq]

You may have reduced the noise, but it is not because of the insulation you have wrapped around the reversing valve. More then likely, while you were installing the insulation, you moved the piping enough to reduce whatever was causing the transfer of sound through the tubing.

I have jambed rocks between the tubing to reduce harmonic and internal sound vibrations. Some manufacturers have heavy rubber kits to dampen the sound, but in all, we are simply transferring the sound producing vibrations into a place where it is not offensive.

If the sound is reduced enough not to bother you, I'd leave it the way it is.

There should be no reason to be concerned about warranty or function. There is nothing that insulation is going to do to harm your system.

[star882]

It might be more work, but have you thought about somehow making the compressor slow down before switching? (Maybe Carrier will come out with a firmware upgrade or new revision of control board?) Of course, you might get more noises when the electronics switch the compressor to slow.

[jrbenny]

I certainly hope you don't have any problems during the warranty period.

I know if you did and I was servicing that unit, there would be a voided warranty on that piece of equipment.
Why? What has he done that would cause problems? Do you insulate your suction lines?

[Gunnery Sergeant Hartman]

Why? What has he done that would cause problems? Do you insulate your suction lines?

Just the fact thatthe HO was tinkering with his equipment while its under warranty.
He should've called the installing company to have them work on the noise.

[RoBoTeq]

Just the fact thatthe HO was tinkering with his equipment while its under warranty.
He should've called the installing company to have them work on the noise.

It is his equipment after all. He didn't really alter the existing equipment in any functional manner. I have had several HOs come up with solutions to annoying sound issues by tinkering with their equipment. After all, the HO is living with the issue 24/7 whereas the issue is not always as prevelant when the professional is at the job.

[mark beiser]

It might be more work, but have you thought about somehow making the compressor slow down before switching? (Maybe Carrier will come out with a firmware upgrade or new revision of control board?) Of course, you might get more noises when the electronics switch the compressor to slow.

Trane defrost controls bring the outdoor fan back on to reduce the head pressure before shifting out of defrost, which makes the shift much quieter. The Trane control also stops the compressor briefly before shifting into defrost.

I think Carrier has a defrost option they call "quiet shift" that does the same thing. I'm not sure if it is an option on the existing control or if it requires that the defrost control be changed.

Adding a control to slow the compressor down would require adding a whole other level of electronics to the system. Something like that wouldn't be a bad idea on an inverter driven compressor though, since it already has all the electronics there for it.

[plain spoken]

Carrier's quiet shift option is not avaiable on this unit and would not help with this issue anyway. The quiet shift does not affect the sound of the reversing valve shifting. It was designed to reduce the sound of the scroll compressor at defrost initation and termination. This unit does not have a scroll compressor so quiet shift was not incorporated into the board.

I agree the switch over noise on these units can be rather loud in high stage. That is why all heat pumps should be installed in an area that the normal noise of operation will not be a nuisance to the homeowner. If this insulation works for you then go for it. It should not hurt a thing and will not affect your warranty.

[mark beiser]

What does Carrier's quiet shift option do?
Anything that reduces the discharge pressure before shifting would make it quieter.

[plain spoken]

As stated, it is to reduce the Copeland scroll noise that is caused by slugging during switch over. It cuts the comprssor off for 30 seconds at beginning and end of defrost to allow the pressures to equilize thus reducing the compressor noise. However reversing valve action is not delayed and its noise is not affected by the quiet shift option.

[jrbenny]

Mark --

Trane does the same thing on their scrolls. Well, they did when I left Trane in 2003.

[mark beiser]

Mark --

Trane does the same thing on their scrolls. Well, they did when I left Trane in 2003.

Trane's defrost control does it regardless of if it is a scroll or not. Turning the compressor off before shifting into defrost, and turning the outdoor fan on before shifting out of defrost does significantly reduce the actual noise of the shift because it lowers the discharge pressure.
Lower discharge pressure = less WOOOSHHHH

If the Carrier option only turns the compressor off, but doesn't delay the shift, I can understand how that doesn't reduce the shifting noise much.

[sillikat]

Thanks for all the feedback, it's much appreciated.

I failed to mention that I have complained to my service company several times about this loud elephant type roar that this makes during defrost shift, and they have responded at least four times. Each time they said it was normal.
But, I don't believe it's normal. The "swooshing" yes, but not this roar. Just a few weeks ago the service tech was here to do the yearly check-up, and he was able to force the reversing valve to make this roar. He too said he thought there was a new board available with a "quiet shift" option from Carrier. His supervisor called, and said he was going to see if it was available. That was the last I heard anything.

The very 1st line in the Installation Manual says to locate this compressor far enough away from the house, so that it doesn't annoy the HO with the noises it makes. I have found that many other persons write that it should also be positioned so it doesn't annoy the neighbors. (It seems that the manufacturer knew this thing was noisy) Wish I had known.

Anyway, I did some searching and found that there is an Acoustic insulation available with instructions on how to construct a sound barrier fence. The fence is like a two side hollowed out slatted redwood fence with the acoustic material as it's core. This information was obtained from the Acoustic Sciences Corp website: http://www.acousticsciences.com/soundfence/heatpump.htm
There are pictures on that page showing some typical installations.

Thanks again . . Tom

[jrbenny]

The very first line of every heat pump installation manual has that kind of language. Every air conditioner installation manual has that kind of language. Many contractors, architects and builders like to ignore that little bit of advice.

[jrbenny]

Trane's defrost control does it regardless of if it is a scroll or not. Turning the compressor off before shifting into defrost, and turning the outdoor fan on before shifting out of defrost does significantly reduce the actual noise of the shift because it lowers the discharge pressure.
Lower discharge pressure = less WOOOSHHHH

If the Carrier option only turns the compressor off, but doesn't delay the shift, I can understand how that doesn't reduce the shifting noise much. The fan delay is there, but for some reason they don't want us to activate the compressor shift feature on the Bristol TS.

[thorton]

Well gentlemen, I have a Carrier 38YZA heat pump with the quiet shift option. It is outside my bedroom window, so noise is a concern. I have tried it both ways (quiet shift & no quiet shift) and can say with assurance that the quiet shift does work. It doesn't quiet the swoosh much, but does quiet the scroll compressor down. However, I'm not using the quiet shift anymore as I don't like all the extra start and stops of the compressor. Too much wear and tear. I personally don't think the quiet shift is a big deal unless the heat pump is close to a sleeping area. There wasn't much of an option to placement of my heat pump because I didn't want it in the front of my house and I had a wide garage between furnace room and the next outside wall.

Thorton
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