Nitrogen Purge Question

[westislandbrewer]

I am new to HVAC and have heard it is best to do a nitrogen purge for the installation of a used unit. Are there any books or references out there that can help me with the specifics on how to go about this? I have 4-5 text books on HVAC but none show how to do it.As I mentioned I have a used unit that the refrigerant has been recovered from. The unit is a 1.5 ton Fujitsu mini split. I really want to reinstall and have this unit work right so I am willing to do more than the standard vacuuming it out. Thanks for any helpful sugestions.....Phil

[Gunslinger]

Use a small stream of nitrogen while brazing. Then pump the system down into a good vacuum, put in nitrogen, release it into the atmosphere, vacuum again, nitrogen again, pump it down again. I use two times unless the system was in bad shape.

[westislandbrewer]

What psig of nitrogen would you recommend while brazing and then to fill once that is done? I have taken the cover off and eveything looks fine. I will be doing a continuity test on compressor just to be sure it's okay. I plan to hook it up in my basement just to be sure it is actually in working order. I would hate to have a surprise once I install it at a future client's house next summer. Speaking of that once I fill with freon and test unit, how long should I run compressor with liquid line closed to collect all the freon in the compressor-condenser (i.e. to get r22 out of the evaporator)? As I mentioned I am new to dealing with used units, usually I just install new units and this is not an issue. But I came across a reasonable deal on ebay for two used units I couldn't pass up on.

[t527ed]

sounds way to diy to me.

[bama 101]

Approx.2 psig of nitrogen flowing thru the system

do not pressurize the system. just allow the nitrogen to flow thru.

[pm4589]

No disrespect, but are you kidding? Sounds like you have just a clue but no idea!

[westislandbrewer]

Your comment doesn't make any sense!!!! I said I was new to HVAC and am asking questions about something I don't know about. Then I am criticized for not knowing something. Duhhhh........... If I knew I wouldn't ask!!!!!!!!!!!!!!!!!! To those who had HELPFUL suggestions thank you very much. I love this field and find it absolutely fascinating. Some knowledge acquired...lots to learn as I previously mentioned.

[dash]

Strongly suggest that register for the Pro Section,once there you'll get a lot more help from other Pros.

In this section ,many members are concerned thay may be giving advice to DIY's and Unlicensed hacks.

[brandonh]

Just curious about the age of the fujitsu minisplit, every one that I have installed in the past 3 years uses flared connections at the evaporator and condenser, and also small line in the line set is not actually the liquid line as the metering device is in the condenser.

[westislandbrewer]

Hello,

I am not sure about the actual age. Was told it was two years old but suspect it is a bit older. I am not sure I understand your question about the flared connections. Every minisplit I have dealt with has flared connections. However I cut and braze the evaporator connection. I just sleep better at night, I know a good flare won't leak but there's even less of a chance with cutting and brazing.

Phil

[brandonh]

I agree with you about the soldered joint being a better joint than the flared however the flared connections are there for service purposes, because some of the service work requires you to remove the evaporator from the wall.