Testing of Mini Splits

Pressure test to above the low-side design pressure. If you test to the pressure of the high side you will blow the low side of the unit.

Dehydration test requires closing the system off the the vacuum pump and seeing if it holds. Its not really a leak test but if you keep it at 500 or 250 microns with the vacuum pump on, you'll get an artificially low reading as the pump is sucking through all the leaks in the fittings. Furthermore, you must isolate the system from the vacuum pump because the whole point of the test is to boil the water into steam, this is a process that takes time, so if you close off the system and the vacuum doesn't hold, it means there is still enough water boiling off.

The test I supervised required 5 minutes of holding below 500 microns, break the vacuum with nitrogen to 50 psig, then hold vacuum at 250 microns for 5 minutes.

Do not let air in the system between the tests and after the test and before the the refrigerant charges. The mechanical contractor must have the fittings set up correctly.