Vacuuming entire split - outdoor unit

[greg_mustang]

Hi All,
The refrigerant of a mini split will be pulled into a recovery bottle in order to do a brazing repair inside the outside unit. Once done, I will have to vacuum the entire unit and put back the refrigerant.
So my question is regarding vacuuming the entire unit. Any risk oil will be sucked out by the pump? I am thinking I need to have the pump and all hoses and guages at a level above the outdoor unit, and I should be fine.
Any issues doing this? How much longer to pull a decent vacuum on the condensor, compressor, etc. vs. linesets and evap ?

Thanks.
Greg

 

[Terry D]

The vacuum pump will not pull the oil out. Doesn't matter where you place the pump. I would pressurize the system with nitrogen after you make the repair and before you evacuate and check your repair for leaking. Put 300 psi into it, use a spray leak detector. Best way to vac a system down is with a micron gauge, I remove the schrader core and use a 3/8 hose, you don't have to, but it eliminates any restrictions. Vac it down to 200 microns, This will go pretty fast on a mini split, close the valves on your gauges or a vacuum rated core removal tool. I don't like using a gauge set, just the micron gauge. Leave it set for 20 minutes, As long as it doesn't raise above 500 microns, you are good to go. And by doing this, you are not checking for leaks, you are insuring that you have removed all non condensables from the system. Pressurizing with nitrogen is for leak checking. If you don't have access to all the tools, I would let the pump run for at least 45 minutes.

Are you planning on putting the refrigerant that you removed, back in the system. If the system was leaking, and this is why you did the repair. There is a good chance you had air in there also. I would advise not to do that. The proper way is to weight in a fresh charge. The name plate on the unit will tell you how much, but you will also need a refrigerant scale. If you have extended the line set from the factory length, you will have to add additional refrigerant for that. The owners manual or online will have that information.

Not everyone does this, but it is also a good idea to purge nitrogen through the system while brazing.

This is a good video on it

 

[greg_mustang]

Thanks for all the info.
My question really was specific to vacuuming the condensor side of the mini-split, never had to do that, only linesets with evap. OK, as I understand it, there is nothing special/different to vacuuming the condensor side as compared to the evap side.

Greg