Recommissioning a mini-split?

[MushCreek]

I say 'recommissioning' because all of the freon has leaked out, so I'm starting from scratch. I have a Mitsubishi mini-split. I know the first thing I need to do is find and repair the system leak. I have a nitrogen set-up to pressure-test the system, and have the flaring tool, should the lines need re-flaring. I have gauges, a micron gauge, a vacuum pump, R410a, and a scale to weigh it in. I've installed several of these unites, but they were all pre-charged. Questions-
1) Do I pressure test it with the ports open or closed? If I close them, how do I know if it's the compressor itself that's leaking?
2) When I evacuate the system, again, ports open or closed? It seems like the compressor would have to be included in the evacuation process.
3) Do I charge it with the ports open or closed?

I've looked all over the web, and can't find info on servicing an empty system. All of the videos pertain to new system installs, or adding refrigerant. BTW- many of the videos, even ones by so-called pros, are just wrong, such as adding refrigerant instead of pumping the system down and weighing in a new charge. Many of them skip pressure testing as well. When I installed my current units, I pressurized them to 500 psi with nitrogen for 24 hours before pumping it down with a micron gauge. Thanks for any help.

 

[Wiz02]

Not an hvac guy, but I like this youtube channel for hvac advice. Have you checked out his videos?

https://youtube.com/@acservicetechchannel?si=H7qNXtD0TC55HNfn

 

[toyotadriver]

Everything open.



Nothing in this post should be misunderstood, interpreted, misinterpreted, or construed to be of a political nature.

 

[brewchief]

If it's a multi head unit you can close off individual heads and pressure test them separately. Final test and vacuum everything open, expect it to take longer to pull a good vacuum.
Pulling a vacuum down below say 1000 microns then adding nitrogen to break vacuum will help remove moisture faster, ideally repeat that 3 times with the last time bringing the vacuum well below 500 before recharging the refrigerant by weight.

 

[justinjoyal]

I say 'recommissioning' because all of the freon has leaked out, so I'm starting from scratch. I have a Mitsubishi mini-split. I know the first thing I need to do is find and repair the system leak. I have a nitrogen set-up to pressure-test the system, and have the flaring tool, should the lines need re-flaring. I have gauges, a micron gauge, a vacuum pump, R410a, and a scale to weigh it in. I've installed several of these unites, but they were all pre-charged. Questions-
1) Do I pressure test it with the ports open or closed? If I close them, how do I know if it's the compressor itself that's leaking?
2) When I evacuate the system, again, ports open or closed? It seems like the compressor would have to be included in the evacuation process.
3) Do I charge it with the ports open or closed?

I've looked all over the web, and can't find info on servicing an empty system. All of the videos pertain to new system installs, or adding refrigerant. BTW- many of the videos, even ones by so-called pros, are just wrong, such as adding refrigerant instead of pumping the system down and weighing in a new charge. Many of them skip pressure testing as well. When I installed my current units, I pressurized them to 500 psi with nitrogen for 24 hours before pumping it down with a micron gauge. Thanks for any help.

1) Open

2) Open

3) Open. Add whatever quantity you can with the system off and turn it on in cooling and add the remaining necessary charge.

 

[MushCreek]

Great! That makes sense to have everything open, since I'll be dealing with the entire system. It's just a single head.

 

[fitter30]

First all system open pressure test 500 lbs. Second test if pressure drops valve off condenser. If you find it ,repaired , retested. Passes triple evacuate to 500 microns or lower.