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Refrigerant leak

Just wanted to know if anyone has found a refrigerant leak with a electronic leak detector with the system charged and running but not have a pressure drop with just nitrogen in the system?
I am curious because I had a small walk in R404A total charge 3 pounds 8 ounces and it is a pump down. It is for a laboratory so they are putting different items in the walk-in but I only saw instruments in there. Service call comes in for not maintaining temperature which is set at 35 degrees it was 58 degrees in the walk in. Unit was low on charge I added approximately 12 ounces of refrigerant. I did a electronic leak search and every time the system would come out of pump down the leak detector would go off it I put the probe close to the indoor coil. I took the detector outside and then came back in and cycled the system again a few more times and the detector would go off every time. When the system pumped down which was about 6-7 psig the detector was not picking up anything. The suction pressure was 62 psig when the system was running near set point. I checked the braze joints and the detector did not pick up anything in either pump down or running mode.
I let the customer know what I found and said I recommend replacing the evaporator coil, customer opted to replace the indoor section not just the coil. A employee who works there said he wanted to do his own test on the evaporator coil when we remove it and he put it in the shop on a bench and pressurized it (I don’t know if he used nitrogen) to 300 psig and called in about 2 weeks later and said that the coil is still holding at 300 psig and I misdiagnosed the leak and ripped them off. I had to go over the leak search with my boss because they are holding payment but I never got to talk to the employee at the lab. I have read about system dependent leaks and I have used dye to find leaks that I could not find with a nitrogen pressure check or a electronic leak detector or a combination of the two but I also never had a customer do their own test like this. I just would like to get some feedback from other techs that have found leaks with a electronic leak detector and not a standing pressure check. Thank you.

Comments

  • icy78icy78 Posts: 315Member
    Leaks can show up in a variety of ways. Vacuum, pressure. At different temps, under vibration, etc.
    I had one recently that leaked only between 20 and 60 psi. I could see the leak at between those pressures but not outside of them. In addition, my H10Pro only detected between those pressures.

    Anyhow, heres a link to help you out. Shoot, I cant link it, so heres a pic of the article.
  • JUGHNEJUGHNE Posts: 6,533Member
    I had a leaker on a 22 year old 2 ton R-22 AC split system.
    Recovered the existing charge, pressured the entire coil, lineset and cond AC up to 300 PSI for hours. No drop.
    I was sure the outside coil that had the 2 rows Al fins rotted away from what I guess was dog urine. But no leak found there.
    So go to evacuation, it would not hold a vacuum. Finally found leaks in the evap coil. Ended up with a complete system change out.

    Never had this happen before......hold high pressure for hours but not hold a vacuum for any length of time. It seemed like the pressure sealed the leak and vacuum sucked it open.

    In your case, the inside coil tested as such on the bench did not include the lineset connections to that coil. Where was the solenoid valve, if any and the TXV? Your replacement may have fixed any of those leaks.
    If the system is working now without loss of charge, they should be happy......you fixed the problem.
  • mattmia2mattmia2 Posts: 861Member
    If it is holding a charge now then that would seem evidence of the leak being in the evaporator somehow.

    did they get the coil cold and see if it involves components shrinking? Could have been the connections as well.

    I can see how resilient seals could seal up at higher pressures but leak at lower pressures or especially under vacuum. See if it holds in the cold under system operating pressures, not a test pressure.
  • Jamie HallJamie Hall Posts: 12,137Member
    May I gently point out something we've all seen or dealt with... and then forgotten? It isn't at all uncommon for connections to leak under a vacuum, and not under pressure -- or vice versa. And when you think about it, it makes sense -- under one the parts are being stressed one way, while under the other the stresses are the opposite.
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • Jolly BodgerJolly Bodger Posts: 209Member
    I had a string of residential split systems on furnaces that would need 2 or 3 pounds every spring. Pumped them down, vacuum, pressure, electronic. Could find no leaks. Replaced Evap coils and system fixed. Took one coil back to the shop and put it under pressure for a week or two. Still could not make it leak.
    The systems would be fine all summer and I think that was a clue. I think the coils would leak in the winter when the furnaces were running and heating up the coils.
  • EBEBRATT-EdEBEBRATT-Ed Posts: 6,557Member
    As @JUGHNE said the best test is to blow it up with nitrogen and let it sit. I like to have it sit all night but you can't always do that.

    Is the system running now and holding the charge with the new coil?? or still leaking even with the new coil?

    If it's working then pressure probably blew something into the coil and plugged the leak or the leak was at the coil connections and was fixed during replacement. Either way you fixed it

    Many chemicals in the atmosphere can make a leak detector go off I like to find leaks with it and use soap to confirm. It can be frustrating. Unusual to pass a pressure test but not hold vacuum
  • JHKJHK Posts: 10Member
    The system has been running and no service calls to my knowledge, I definitely would of heard about if it came back in for low on charge. Thank you for all the replies.
  • JHKJHK Posts: 10Member
    The only test I am aware of that the employee did was at room temperature probably in the 68-72 degree range in the shop. I never spoke to the employee after I was done that day but I do not think he would of thought to do anything but just a standing pressure check in the shop. He is not a service technician or a former service technician but from what I saw he has a lot of down time and he is a know it all type.
  • pecmsgpecmsg Posts: 1,135Member
    Ill agree with standing pressure test being more accurate.

    Going into the box and having a leak detector go off is just a sign. X-Valve, Solenoid valve, refrigeration tubing ALL could be the cause of the leak as well as the evaporator coil it self. Did you drop the drain pan and look for oil or stains?

    I would have advised the customer we would like to pump the unit down, isolate the condensing unit, line set and evaporator to isolate what component is leaking. This puts the responsibility back in there court.
  • icy78icy78 Posts: 315Member
    > @pecmsg said:
    > Ill agree with standing pressure test being more accurate.
    >
    > Going into the box and having a leak detector go off is just a sign. X-Valve, Solenoid valve, refrigeration tubing ALL could be the cause of the leak as well as the evaporator coil it self. Did you drop the drain pan and look for oil or stains?
    >
    > I would have advised the customer we would like to pump the unit down, isolate the condensing unit, line set and evaporator to isolate what component is leaking. This puts the responsibility back in there court.

    Yes.^^^^^

    In small sized air conditioning work, often guys will condemn an evaporator simply by putting the electronic sniffer in the evaporator section and getting a consistant hit. As pecmsg points out, in Refrigeration, there are other items that could/should be carefully checked also.

    @JHK did you read the literature I posted?. (Its not just a BigBlu add🙂)
  • JHKJHK Posts: 10Member
    Yes I did read the literature it was very good, I saved it on my phone.
    The evaporator coil, solenoid and txv are all under the employees pressure check I changed out the whole unit just not the coil because they opted to change the unit not just the coil. I do like the isolated pressure check but according to the information I just read that Icy78 linked there are scenarios where a standing pressure check will not determine where the refrigerant leak is coming from. Thank you for all the replies I do appreciate it.
  • mikeg2015mikeg2015 Posts: 1,126Member
    This kind of BS drive some nuts. The customer running their own “test” and telling you it’s OK and you ripped them off.

    Bottom line, it was low on refrigerant before, therefore it had a leak.

    It does not leak now, therefore the leak was fixed.

    Customer must pay. Why is that complicated? Sorry, but half the corporate purchasing guys I’ve met are jerks that assume every contractor is trying ot rip them off. We have one right now as a customer and is a total PITA. Passive aggressive, monotone, no sense of humor and little empathy.
  • unclejohnunclejohn Posts: 1,453Member
    If they refuse to pay go get your equipment back and they can reinstall the old stuff.
  • motoguy128motoguy128 Posts: 48Member
    When I was a facilities engineer. Most of the contractors required 50% down for equipment t we had to order for this reason. At worst, you lost profit and most of the labor.

    Do the same for residential at my company now. Need a check before Equipment arrives on site.
  • motoguy128motoguy128 Posts: 48Member
    ... plus legally, I think once the equipment it’s on site, the customer has possession and therefore owns it. You need a court order to get it back.
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