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48K Mitsubishi H2i pressure test results

agooch | Posted in General Questions on

I’ve done probably a half dozen single zone mini split installs.  I always pressurize the (only) low side service port to 200psi and then move to evac after an hour assuming no loss.

This one is for my own home and has been a job.  It uses a branch box for 5 zones.  Going by the book for a change, and it says pressurize both 1/4” service ports to 600psi overnight.  After an hour last night, steady at 600 so went to bed.  This AM I show I’ve lost 200 psi on high side, but low side is still perfect.

I don’t understand, shouldn’t they equalize?  I’ve never even pressurized the high side in the past.  Appreciate any and all input, 12f in Kansas today and we have a new baby who’s reacting poorly to our wood stove.  Thank you!

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  1. walta100 | | #1

    Sure sounds like a leak.

    I would fill it back up and spray every joint with soap water 409 cleaner works good.

    The fact that it is not equalizing could help you find the leak. Depending on what valves were closed.

    The connection for your gage is the most likely leak if it was not valved off.

    1. agooch | | #2

      I had to make a trip for bubbles that won’t freeze at 12f, haha. Got everything soaped up now and no bubbles yet... never have I ever WANTED to see bubbles before.

      1. agooch | | #3

        Welp, winner winner chicken dinner. It was the gauge leaking. So much for fancy yellow jacket hoses!

  2. walta100 | | #4

    You found one leak that is not to say you have no more leaks. Put it back to 600 close the valve to the gage and test again. Then read the gage tomorrow.


    1. agooch | | #5

      That’s exactly what I did. Core removal tools don’t fit on these service ports (no room) so I just added 45’s with ball valves and shut off right after ports.

      Even my low temp bubbles were freezing last night so it’s hard to say for sure... but anything with an o-ring is proving hard to get a perfect seal in this weather.

  3. walta100 | | #6

    Be aware you can get replacement rubber seals to fit Yellow Jacket hoses if they are worn or damaged.


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