The nitrogen pressure test on a new system revealed a small leak at the large cap on the suction service valve ( possibly the result of too much heat heat when brazing?? ). After 3-4 wraps of teflon tape around the threads and tightening it down with a moderate amount of torque, the system is now solid at the 150 psi pressure test. It then pulled 50 microns while evacuating, raising to 500 microns after pump shutdown and holding steady at that level for 45 minutes. So, by these measures the system is leak free.
Short of changing out the service valve, the current plan is to open the liquid service valve first, allowing the condenser pre-charge to break the vacuum and somewhat pressurize the system. The "sealed " suction valve cap would then be removed to open the valve, then resealed using the best method possible. It is unclear whether internal valve conitions will get better or worse after opening the valve. Any input on this would be greatly appreciated. In particular, is there a best way to create a good seal at the cap? ( For what it's worth, the valve is made by Sporlan). Thanks