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p.i.t.a refrigerant leak

Never had a leak like this. When I install a new system, I pressurize the lineset with 200# of pressure with nitrogen before evacuating. I did that with this job and it seemed fine. To make a long story short, I had to go back several times over the last couple of months to re-fill because there was a leak. This is a townhouse so lineset couldnt be replaced because it was ran in the walls. Today I cut the liquid and suction lines at the evaporator coil and brazed the ends shut, then pressurized each line seperately with 300 psi. Obviously I pumped down what refrigerant was in the system first. Sure enough the suction line dropped about 30 psi in an hr. Liquid line held. Why didn't this show up in the original test I did? The vacuum even held under 1000 microns for over a minute.


  • meplumber
    meplumber Member Posts: 678
    Siding Nail?

    I once had this happen. Although it was a long time ago. Long story short, the siding guys used one coil of longer nails when they put the cedar shingles on. The leak didn't show up at first. Only after the building had expanded and contracted a few times and the nail worked its way loose and opened up the hole.

    Not sure if this is your problem, but maybe it gives you an idea.

    Please note that back in those days, we were less likely to pressure test to as high a pressure as we all do now. Back then we would just throw 100# of nitrogen on it, go to lunch and if it held, it was good.

    Now we know better, huh?

    Good Luck
  • tim smith
    tim smith Member Posts: 2,498
    Re: check for leaks

    I assume this is r410? correct.  1st off, your test pressure should have been around 450 - 500 psi. 2nd off, vacuum should have been pulled down to 300 or lower and then should not rise above 400 in 10 minutes. This varies some by each mfr or trade publication but I think a good avg basis. Each tech probably has a varying opinion but I do not think above is over doing it.   
  • drhvac
    drhvac Member Posts: 190
    500 psi?

    No you go by what the manufacturer tells you the test pressure is. This one said 300 psi. The leak was found in the suction line somewhere buried in the ceiling of the tenants below. This was done by cutting the suction and liquid lines and brazing shut at the evaporator coil. Then if you want you could pump the pressure up to 500psi because the evaporator coil is not seeing it. The suction pressure dropped 25 psi within a half hr. Upon my next visit it was empty while the liquid line remained at 300 psi.. The coil was isolated as well and held pressure. Now we are waiting to hear from the condo board on whether or not they will approve us running a new lineset up the side of the building.
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