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  1. #1
    Join Date
    Dec 2011
    Location
    San Antonio, TX
    Posts
    381

    Double / triple sweep?

    Does anyone actually do this? I don't see the reason for it and have been told by some its a waste of time. I've never even seen it done but I've heard people talk about it.

    Pull a vacuum and hold your microns. What are yalls thoughts on this?

  2. #2
    Join Date
    Sep 2009
    Location
    Hampton, GA
    Posts
    517
    Its in my school book. But also your right...not many people probably do it. Loll , too much back and forth with nitro and releasing it and pulling another vacuum. It also says to just pull a deep vacuum to 500 microns and then watch if vacuum holds or see if microns go up; indicating there is maybe still moisture in the system.

  3. #3
    Join Date
    Mar 2007
    Posts
    3,103
    It's a waste of time and material, IMO.
    "There is no greater inequality than the equal treatment of unequals."

    -Thomas Jefferson

  4. #4
    It sure is a waste.

  5. #5
    Join Date
    Jun 2003
    Location
    Tampa Bay, FL.
    Posts
    119
    In small,capillary refer systems; I find that it does help when I'm having trouble getting to 500 mics. May not be as useful in residential work but has definitely helped me.

  6. #6
    Join Date
    Oct 2002
    Posts
    1,248
    Always do this on freezer equipment. Very dry Nitrogen picks up moisture more easily than straight vacuum and moisture is removed.

    Like rinsing out that milk jug before it hits the trash.

  7. #7
    I know right?

  8. #8
    Join Date
    Sep 2012
    Location
    NW Louisiana
    Posts
    159
    Quote Originally Posted by dsprice View Post
    Does anyone actually do this? I don't see the reason for it and have been told by some its a waste of time. I've never even seen it done but I've heard people talk about it.

    Pull a vacuum and hold your microns. What are yalls thoughts on this?
    I know for a fact in my area N2 purge is not done. I have had employees tell me they do not. Most don't even use a micron gauge. Its more common than you think. Same thing goes for recovery machines.

    Personally on my two HP's I installed on my new house this is how I did it. I pressure tested the line set with tracer gas, then leak checked. Each unit had 1 leak. Vented N2 and repaired. Pressure tested again with tracer, no leaks. Purged twice more with N2 then pulled vacuum down to 300 microns. The reason I was so OCD with the N2 was I roughed in my lines about 4-5 months before I installed the units. I did have them capped, but wanted to make sure they were DRY! So Basically I shot N2 through 4 times per system. One unit had about 80 ft of line set.

    CT

  9. #9
    Join Date
    Jun 2009
    Location
    Upstate SC
    Posts
    1,439
    Systems that have moisture shows the greatest reward when doing a triple evacuation. It uses a lot of nitrogen but nitrogen is CHEAP and if a triple evac and sweep saves me 45 minutes pulling a vacuum then I'm game.

    Sent from my ERIS using Tapatalk 2

  10. #10
    Join Date
    May 2009
    Posts
    264
    If you can pull a vacuum down to 150 microns and hold for 10 minutes....it's good.

    I would definitely recommend appion vacuum rated valve core removal tools....they allow the vacuum to be pulled in 15 minutes on residential systems. And a CPS micron gauge.

  11. #11
    Join Date
    Jul 2009
    Location
    Columbia, MD
    Posts
    3,788
    You only need to do a triple evac when your having trouble pulling down.

    If you have a very wet system, a slow low pressure purge is the best. if you shoot 400psi thru, it does no good.

    Remember, nice, SLOW, N2 purge. then re-evacuate.

    If you use a good evacuation setup it is in-fact pretty easy and fast.

  12. #12
    Join Date
    Oct 2002
    Posts
    1,248
    just remove cores before pulling vacuum. After pulling vacuum, add Freon untill about 2 psi, remove hoses and install cores.

  13. #13
    Join Date
    Jul 2010
    Location
    nebraska
    Posts
    1,629
    We always break a vacuum at least once with dry nitro after 1000 micron then pull it down again to below 500. Was taught that a very fast vac can make the moisture freeze and the dry nitro was to get it into vapor form. Might have been an old wifes tale but see no need to test the theory for $1 worth of nitro and an extra minute of time.

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