:confused:

How were they able to vacuum the system down if there was a leak? On 9/26 they apparently pulled to 450 microns.

That is an excellent question.

The original vacuum test only tests the line sets and inside units, not the outside unit because the isolation valves are closed. So maybe that's why they were thinking there might be a leak inside the outdoor unit. The current nitrogen pressure tests don't seem to indicate leaks currently.

I watched them pull it down and "hold" it. Yes, pulled to 450 microns. The vacuum hold test was not perfect rising about 1-2 microns/minute. Maybe the pump was able to pull faster than the leak and get to 450. ??

Update. It appears after 1 week of holding ~550psi of nitrogen there is not a leak after fixing the flare fitting. They dumped the nitrogen, vacuumed and filled with ~9 pounds of R410a. Turned it on and tested cooling and heating full performance and things seems to work.
So after 2 months of emailing/etc. several tech. visits to find what seems to be a badly formed flare joint, the system is now working as it should. Fingers crossed.
Right now I'm not positively impressed with the quality of the people that install these things. The company I choose is considered near the top in my area.

Thanks for the update and glad things eventually worked out!