# Vibration in refrigerant supply line



## gregzoll (Dec 25, 2006)

If you did not feel the liquid movement or hear the hum, then yes there would be a problem with your system. My guess is that you have a heat pump, not a standard air conditioner.


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## Doc Holliday (Mar 12, 2011)

It sounds like a thermostatic expansion valve doing it's job.


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## slickwilliam (Nov 18, 2010)

Thanks for your replies. It is not a heat-pump (hence the furnace replacement) and I would expect an expansion valve to operate more smoothly.

Well, we'll just keep an eye on it and see what happens. It's working right now, so there's no urgency. (That'll likely change when it finally breaks entirely in August... :laughing: )

Again, thanks...


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## Doc Holliday (Mar 12, 2011)

An expansion valve when closed makes for a higher pressure. When it opens the pressure releases on the refrigerant in the high side line. It is always opening and closing, you can see it on refrigerant gauges. 

Anyway, that's just one possible suspect. I've come across the lines vibrating when the condenser was blocked resulting in extremely high head pressure.

It also could be that you have a kink in the lineset somewhere. All I can do is speculate from here.


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## Marty S. (Oct 31, 2009)

Also could be low on charge due to a leak as you suspected. Once it's low enough to lose subcooled liquid in the line no longer stays in a liquid state the whole way to the metering device. Sounds and feels like air bubbles in the line since the refrigerant is changing from liquid to a vapor.


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## slickwilliam (Nov 18, 2010)

Thanks, Doc. I would expect an expansion valve to be much more of a gradual change and temps/pressures gradually built-up or changed in the system. These are pretty sharp pulses, happening once or twice a second. 

Marty, I think you may be correct. It does indeed feel like flow turbulence in the line, much like a garden hose that has some air bubbles in it when first turned on. And the low refrigerant seems like a reasonable guess as the furnace install crew pretty-well manhandled the coil/plenum assembly when they replaced the furnace beneath it. It wouldn't surprise me to find a hairline crack in one on the lines' solder joints. Or the line itself for that matter. I think I'll have them come out and check refrigerant levels...

Again, thanks all for your replies, and have a great evening...

Bill


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