Ok guys, I will start by saying forgive me if this seems like a diy question. I have been out of the hvac field for 6 years and back in it for about 8 months. Im just trying to get back up to speed.
I was hooking up an older rheem unit today (homeowner had some landscaping done over winter so they had it in a basment for awhile) and i put a new dryer on it and re brazed the line set. I pumped 368 lbs of nitrogen in it to check my welds and let it sit for about 4 1/2 hours while i went to check on another customer. when i got back it was still on 368 lbs of pressure, so i pumped it down to 430 microns, when i turned the pump off the microns never restabilzed and within 20 mins was back up to 1500 microns. Normally i would say there was a leak somwhere in the system. so i pumped it back up with nitrogen and checked all the welds and all around the system for leaks, never even got a small bubble. re-pumped it back down to 450 microns, and within 20 mins again it was back to 1500 and climbing. Anyone have any ideas of whats going on? All help is greatly appreciated.