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Thread: txv question?

  1. #1
    Join Date
    Sep 2010
    Location
    miami,fl.
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    623

    txv question?

    i replaced a txv on a trane a/H ordered factory valve and installed. i pressurize system to 300 psig through my high side it kept droppping so i figured hmm i have a leak, isolate liquid and suction lines they both hold ok its in my evap coil.
    so i put a gage port on the liquid line entering txv pressurize to 300psig and it drops im going crazy for this leak so i put a gage port on my suction sideof the evap coil, then i realize its pissing through the valve slow. i heat the bulb a little and pops open cool. but here is where it gets me. if i pressurize through the txv inlet side it will hold 300psig and only go up to 175 max on the out bound side, so i pressurize in reverse through suction now its the opposite. evap side holds 300 and txv inlet will max out at 175psig its something about the pressure differential across the valve that makes it close up it my only thought never seen one act that way???????? any body encounter that or know of it?

  2. #2
    Join Date
    Jun 2009
    Location
    NYC
    Posts
    457
    When I pressure test a system, I equalize both sides through my manifold gauges to prevent stuff like this from tricking me into thinking there is a leak. It's the same for pulling a vacuum.

  3. #3
    Join Date
    Oct 2011
    Location
    Chicagoland Area
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    4,615
    There are some old R12 valves that won't go above 50psi when pressurized.
    Officially, Down for the count

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  4. #4
    Join Date
    Sep 2010
    Location
    miami,fl.
    Posts
    623
    Quote Originally Posted by keviekev70 View Post
    When I pressure test a system, I equalize both sides through my manifold gauges to prevent stuff like this from tricking me into thinking there is a leak. It's the same for pulling a vacuum.
    i stopped pressurizing through my low side gage because to much pressure will cause it to warp out the bourdon tube inside the low side gage (analog style) i do have a set for 410 but i prefer the lower pressure gage gives smaller increments for setting pressure controls and stuff. i guess i could have left on the lo side gage until it got up around its max then removed ill start doing it that way. i must say i wasted an extra 2 hrs messing around looking for a leak.

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