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I am finishing up a 6 zone mini split DIY installation and before closing up some of the walls I would like to do some leak checks. My set up is that from the condenser it splits into 2 branch boxes and from there on to 3 evaporators each. I would like to check before I call out the HVAC to charge with the few ounces of r410a I need. I don’t want to hold them up with doing the triple check and was hoping to test it myself. I am willing buy the parts but finding hydrogen in a small amount. Any idea to help me get the pressure leak test done.

  • I should have mentioned you can rent small nitrogen bottles but you must have a regulator , bottle pressure will blow even a 410 system , I want to say burst is 800 psi but that may be my hoses I am thinking of. I think fresh nitrogen bottle pressure is just over 2000 (Co2 will also work again bottle pressure ~2000+psi but most recommend nitrogen but most non reactive gasses will work) I mentioned Co2 as some people have this for beer or sodas. And or welding. – Ed Beal Jul 28 '20 at 22:55
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This is really for licensed people, the system needs to be evacuated prior to charging.
If you have the correct adapters you could pressurize the system to 120 psi with nitrogen (don’t use air it is dirty and wet) let the system sit for 15 minutes to see if you loose pressure this is a gross leak test and can identify larger leaks.

The hvac guys will need to pull a vacuum on the system to remove the air (non compressible in hvac terms) and any moisture , they will usually do a leak back check no change in pressure then charge the system and checks for leaks with a detector.

We use nitrogen for leak checking because it is clean and dry. Using air from your home compressor can contaminate the line set with moisture and possibly compressor oil. Other than this if you have a vacuum pump you could pull a vacuum on the system , EPA recommends a base pressure below 500 microns of vacuum I like keeping a new system at high vac for several hours or even overnight to fully remove any moisture. Anything beyond this would require a licensed technician in most countries. In the US fines up to $25,000.00 For unlicensed person charging a system, the compressor has the charge opening that valve and allowing Freon to fill the line set is charging the system.

So to stay safe don’t go any further than a pressure / vacuum leak test on your line set.

  • Right - that is why I am having the HVAC guys come out for the vacuum pull and charge. No intentions on doing the charge. To be honest, my biggest fear is them coming out and finding a leaky system. Also, want to make sure the each of the six line sets do not have a leak before I put up the drywall patch work and have to tear it down again. – ecco88 Jul 28 '20 at 22:06
  • Did you re do any factory flairs? I find most of the ones even some high end models come with really crappy flair jobs. I would wait if at all possible I have had systems pass 120 psi nitrogen no bubbles at any of the connections but fail a vacuum leak check or charged system test the evaporator was the problem once the other A compressor. If you have the wall sealed up you might not be able to find the leak and if at the evaporator and your lines are inside the walls you will need to re open them. Were You critical of the flairs redoing any bad ones ? the risk of having to open the walls ~1% – Ed Beal Jul 28 '20 at 22:39
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    Line sets did not come from the factory - and I didn’t get the pre flaired because I thought I would just cut and do my own cuts anyway. – ecco88 Jul 29 '20 at 3:30

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