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Can't get minisplit outdoor unit to stay at 500 microns
So....I installed a Fujitsu several weeks ago. At the end of a long cold day I had evacuated the lineset/indoor unit down into double digit microns and it held rock steady. This was after the N2 pressure leak test. Then I released the factory charge. That night something got in my head that I had allowed air into the system somewhere in between the evacuation and the release.
No biggie, to play it safe and do it right I'll just recover the 2.5lb charge and install virgin 410.
After the recovery, I pulled two vacuums with an N2 purge in between. I can easily reach 500 microns on the line set in < 2mins with the service valves closed. Once I open the valves, I can get to 500 again in about 10-15 mins and go down to 400 but...my gauge marches micron by micron up to 800 after 5 mins. If I repeatedly bring it back down to 400, that micron march slows to about <0.1 micron a second which is ~ 5-6 microns/minute.
I've repeated that process many times to get to that point.
What is it that is incrementally adding these microns?
Do I need to flush the system with a anti-micronial solution?