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Nitrogen leak checking

it can save a group of mind boggling at times.:)


  • My girlfreind hates this website because she knows if I'm on it, she's not going to see me for a while. You guys are the best.
    I leaked check a system the other day at 250 psi and it held for 15 minutes. Perfomed evacuation, recharged and called it good. Two hours later, the unit was out again on low pressure. Is it better to check a system for a leak at a higher pressure or a lower pressure and how musch time do I allow before I s/b confident a leak doesn't exist(assume residential w/ 50 ft lineset). Why didn't my guage move?
  • jim lockard
    jim lockard Member Posts: 1,059

    Darin- What was the reading on your vacuum gauge? with a 3 minute rise? If you can pull a 300 to 500 mic. vacuum with a 150 mic rise you should be tight. If you have a nail or a screw in the line set, it may hold vacuum or pressure but not both. How about your schrade valves caps on tight?Best Wishes J.Lockard
  • Techman
    Techman Member Posts: 2,144
    Hi Darin

    What were your pressurers/temps at start-up?Evap blower motor seizing up?Stay and watch system run for an hour?
    Higher pressure is better for leak testing,and as Jim said ,check the schrader inserts!Let us know what happens!
  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380
    Just for the record

    Make certain to check the test pressures on the nameplates of the system co mponents. You should never leak test at a pressure that exceeds the LOWEST test pressure. FOr example, your condensing unit may be pressure tested at the factory up to 300 psig and your air handler (R-22, non heat pump) is likely pressure tested to 150 psig. So, when you are pressurizing the assembled unit, your test pressure should not exceddd the lowest pressure, or 150 psig.
  • jim lockard
    jim lockard Member Posts: 1,059

    Would it not be great if someone made a 6" test gauge (or maybe they do)that we could hook up 150 psi of nitrogen to and watch for 15 min. rather then depending on a 21/2 or 3" gauge set. (then you could really see your leak Darin) Best Wishes J.Lockard
  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380
    Indeed it Would Jim

    I would love to see it.
  • Jim Bergmann_2
    Jim Bergmann_2 Member Posts: 79
    High Resolution Gauge

    Another advantage of digital gauges like the Testo 523, .1 psi resolution, 750 psi working pressure on both sides. A standard high side gauge has to drop 5 psi to move one increment. A digital manifold .1 psi, 50 times the resolution of a standard manifold for pressure testing. Also they use a leak test mode and the perfect gas law to determine if the pressure is changing due to a leak or a temperature change.
  • TomStayer
    TomStayer Member Posts: 38
    Leaking AC


    Have you ruled out damaged schrader valve stems? You will not see this leak because your gauges are on the valves.

  • Darin(in Michigan)
    Darin(in Michigan) Member Posts: 90
    Nitrogen and leak checking

    Thanks for the input guys. No, he shraders were fine. The leak was under some insulation near the evaporator. It was a pretty big leak(I should have caught it the first time). Its funny how the system was fine for years and then "pow"- a leak on a brazed joint. I guess thats why I blamed the leak on leaking service valve packing the first time. I actually got lucky. The entire lineset(both liquid and suction)were insulated and a good portion is in a stud cavity and above drop ceiling tiles). To err is human to forgive is not company policy.:)
  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380

    Glad to hear the system is up and running again.

    Keep up the good work.
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