Noise at evap coil

[Metoob]

Hi, I was cleaning a residential ac unit last week, and I noticed something weird.
Whenever the compressor started, there would be a loud whooshing noise at the evap coil, sorta like opening a valve on a tank, except muffled. The noise lasts about 2-3 seconds each time.
This is a 2.5 ton 410 unit without a txv, about 2 years old.
Speaking to the homeowner It has done it since new. The unit cools well, and I didn’t hook up the gauges to it.
Any idea what might be causing this?

[Ammar.almahdi]

Is this a heat pump or straight ac?


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[Metoob]

AC


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[Ammar.almahdi]

So did it work fine after u cleaned it? Sure that noise wasnt a big hole in the evap ?


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[Metoob]

Unit cools good. I only cleaned the condenser coil, the evap was clean.


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[heatingman]

Thats the sound of gas blowing through the metering device. At start up, its mainly gas in the liquid line.


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[Nosalesman]

That's normal, gas being pumped through your liquid line as heatingman said. You're never going to start a unit and not heat the refer moving. A constant loud swish might indicate an issue though.

[knave]

You can hear it on expansion valves also. Listen for the liquid seal to hit, the “dry” TXVs really whistle.

[Metoob]

You can hear it on expansion valves also. Listen for the liquid seal to hit, the “dry” TXVs really whistle.

I guess I’ve never heard it that loud before, I was just wondering if it’s normal. I suppose it is. Thanks!


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[Ac_man]

Check the refrigerant pressures, sometimes it’s other things like low refrigerant which can indicate a possible leak,non condensables or not topped off since it’s fairly new.

[eddiek]

Thats the sound of gas blowing through the metering device. At start up, its mainly gas in the liquid line.


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^^^^ THIS ^^^^ Probably a non bleed