Heat Pump "Flushing" Noise

Old 03-22-04, 09:44 PM
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Heat Pump "Flushing" Noise

I have two American Standard heat pumps which have been getting progressively more noisy over the past three years during the cold seasons. When first installed in our new home three years ago, we did not have the loud "flushing" noise we have had this season.

I had the guy who installed the units originally inspect them and he keeps telling me the had to have made the same noise three years ago if they were working properly then as he seemed to think they were working properly now. He even took the cover off the compressors outside and manually cycled the valve which when activated, made a noise similar to someone flushing a vacuum activated toilet at a public restroom. The valve he actuated was the one that defrosts the coils during temperatures in the 20s to 30s.

His explaination was convincing but the fact is...the noise was not there in past seasons like it is now. Not being an expert but mechanically knowledgeable, I asked him to check the refrigerant level for my own satisfaction, which he did, and he said it was right where it should be.

When the specific valve is cycled, the noise radiates throughout the plumbing going from the compressors outside to the units beneathe the home in the crawlspace. Could it be air trapped in the system?

Hope you can explain or help me troubleshoot.

Bob in Kentucky
Old 03-23-04, 03:45 AM
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Our home has been on heat pumps since 1977, and it sounds normal to me.
I've never noticed that they might seem to get louder with age and usage, but maybe they do.
I'm not an HVAC technician. Maybe one here can explain it.
Old 03-23-04, 04:37 AM
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I'm surprised you didn't hear it before. That sound is the reversing valve changing direction of the refrigerant flow to defrost the outdoor coils. American Standard is a very good unit and if maintained will last a long time.
Old 03-23-04, 06:12 AM
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With them all here . Over 30 years with heatpumps and they all make that flushing noise. Air in the lines No way.just freon in a gas form ED
Old 03-24-04, 05:50 PM
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i agree, sounds normal. have the charge checked to be sure it is not low, this may cause noise in the lineset. also be sure the outdoor and indoor coils are clean, high pressures due to dirty coils also contribute to lineset noise.
Old 03-29-04, 05:56 PM
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Being flushed

If I had a heat pump, I'd be concerned if I didn't hear the flushing sound...This is the reversing valve being energized to run in the AC mode BUT without the outdoor fan running. Then it reverses and you'll hear the swooshing sound of the hot gas reversing it direction of travel...and the outdoor fan will start. If the unit vibrates into the house you might get some Neoprene type mounts that fit into unistrut called a vibraclamp. I think residental units now have this type of plastic style pipe mount that might help reduce sound transmission. Maybe when the trees get their foilage again you won't hear it as loud.. There is no concern though... Sounds like you got a smart tech to service your equipment...Good for You!

Old 03-30-04, 05:39 AM
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On a related note.....I used to work on a lot of ice machines. They use a hot gas reversing valve to strip the ice off the collecting plates when the cycle is done. They all make a fairly loud flushing noise as the refrigerant reversed flow through what is usually the evaporator. Heat pumps do the same thing only you don't put the ice that falls off in your drinks.

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