I found the nitrogen test pretty easy, since I already had a paint-ball air tank.
They are cheap and come with a 800-900 PSI regulator built in.
Hooking one up to your manifold isn't much of a problem..
But, there is a work-around, that's fairly common in these kinds of installations.
After you have done your vacuum testing, and everything looks good,
and you are at the 'release the 410a' step. Stop right there.
Read over your manual, it might even tell you how to do this pressure test.
You release 410a into the line-set for 10 or 15 seconds, and then shut off the valve.
If there is a loose fitting, you won't suffer a big loss of refrigerant.
Now is the time to check all your flare fittings with soapy water.
You might also have a stethoscope handy to 'listen' to the fittings.
I use one from an old BP tester. Just removed the big disc on the end of the hose.
Or, you can just use 3' of flexible tubing, holding one end to your ear and the other near the fittings.
That worked very well for me, when I was on the phone with Sanyo,
I was able to 'pipe' the hissing sound to the phone. Making my case for a leak right above the compressor.
Anyways, when you don't detect any leaks, then you can release the 410a for real.
I did this 401a pressure test with my Sanyo (both times I installed) and it
gave me confidence in the flares.
I guess you could do this test with a manifold attached and just watch the pressure for a couple of days..
Since my line-set was pre-flared and was so simple (4 connections),
I tried to keep it simple and not have to waste any 410a in the hoses.
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