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  1. #1
    Join Date
    Apr 2004
    Location
    NJ
    Posts
    155

    Confused Discharge check valve chattering

    Greetings all. I have been asked for advice concerning an intermittent discharge check valve chatter on a subway car air conditioner. It is a Carrier Open Drive 10 ton R- 22 unit with a typical Henry discharge check valve. The compressor was overcharged with oil (the oil entirely fills the sight glass while the compressor is running). I am told that refrigerant charge was weighed in according to manufacturer specs. Coils are new (therefore clean). Compressor is re-built. I thought that being the compressor is rebuilt, a reed valve may have been slight bent, causing a momentary pressure fluctuation that would cause the check valve chatter, but the pressure gauge does not indicate any fluctuation (no "flutter").

    They are re-conditioning their hvac-units and have completed about 100. This problem occured on about a dozen of them.

    Is it possible the severe overcharge of oil is causing adhesion of the checkvalve to its cage?

    Appreciate any help you guys can offer.

  2. #2
    Join Date
    Apr 2004
    Location
    Rossville, GA
    Posts
    104
    What kind of check valve (3 basic types) do you have? I take it the you have a split system ac system being that it is an open drive. If so, is the compressor below the evaporator? Oil overcharging is worst than low oil level. You may have found your problem with spring loaded check valve chattering due to oil over charging an/or oil loggin. Condensing temperature is also critical for this type of accessory to work properly. Good luck

  3. #3
    A compressor overcharged with oil will cause noise and vibration and if it is overcharged to fill the bullseye you will have a lot of vibration and noise.

  4. #4
    Join Date
    Apr 2004
    Location
    NJ
    Posts
    155
    Thanks Gas. It is a split with the compressor under the car body and the evap in the interior (passenger compartment) "attic". Also, it is a spring loaded check. Condensing temp was low, but I covered the coil and ran it until pressure was close to 300psig to see if noise would abate but it didn't. I'm actually the HVAC Instructor/EPA Certification Officer for this Transit System, and they asked for my input.

  5. #5
    Join Date
    Apr 2004
    Location
    NJ
    Posts
    155
    I agree Pro. But I actually held the check and felt it chattering.

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