deep vacs on racks - Page 2
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  1. #14
    Join Date
    Sep 2001
    Location
    East Stroudsburg, PA
    Posts
    13,215
    Personally, I'm with R12 on the service evac. I carry three 7 cfm pumps in my truck, and if a mojor component has to be serviced, like a condenser, or a reclaim coil, etc. All three are going on there, for as long as I can stall the store managers.

    I prefer to have ball valves everywhere, and I do mean everywhere, but on most older systems, you don't have that.

    There is a thread on dirty oil right now, and I mentioned cleaning the separator.

    The oil separator is the one component that everyone in mfg and install ignores. There should not only be lockoff valves on either side of it, but there should, IMO, be a bypass around it for cleaning it. I've installed several now, and they are the only way to go. You just need to make sure that the bypass is CLEARLY MARKED IN A HEAT RESISTANT MANNER that it is a normally closed valve, and should NEVER be left open, except during cleaning procedures. This type of thing speeds up evacuation during service.

    As far as initial startup, I am more inclined to connect ten 7 cfm pumps to various points of the system, rather than one large pump.

    I've seen one large pump left on lose a belt when no one was around, and then you lose your vacuum.

    If you can stay and watch it, I suppose it's ok, but I wouldn't want to babysit a large rack overnight.

    Every rack that I've started has been down to and held 300 microns. I think that is sufficient. I've also never watched a pump run, though. Go home, leave those ten puppies run, come back in the morning and check it. Not many contractors want to invest in a pump that large, anyway.

    3 grand for 10 pumps is a lot easier to swallow than 2 grand for one...

  2. #15
    Join Date
    Sep 2001
    Location
    East Stroudsburg, PA
    Posts
    13,215
    Also, with 10 7 cfm pumps, as opposed to the OP's 1 26 cfm, I'm well over double the air removing capacity.

    The only problem is the waste of vacuum oil in my method, and the time to change oil and make multiple connections.

    I can't think of anyone nearby here that uses a single large pump for rack startups, though.

    It's not a bad plan, though.

  3. #16
    Join Date
    Sep 2001
    Location
    East Stroudsburg, PA
    Posts
    13,215
    Of course, I jsut reread the original post, where he's saying 4-5 days to evacuate a rack. I would be strung up from the nearest crane if I ever told a job super 4-5 days to evacuate.

    My process takes about 2.5 days, total, with the pumps running overnight. In MILD WEATHER. If it's real cold out, then it might take 3 days.

  4. #17
    Originally posted by condenseddave
    Personally, I'm with R12 on the service evac. I carry three 7 cfm pumps in my truck, and if a mojor component has to be serviced, like a condenser, or a reclaim coil, etc. All three are going on there, for as long as I can stall the store managers.
    Dogone Dave, maybe paying attention to your words over the years is paying off.
    Maybe I'm catching on here ..... ya think?


    By the way, that comment about 300 microns ... was that only on a start up of a brand stinking new system?



    What would you pull a circuit down to if you just replaced the coil in a service meat case?
    (leaking ball valves and all)


  5. #18
    Join Date
    Sep 2001
    Location
    East Stroudsburg, PA
    Posts
    13,215
    Originally posted by R12rules
    By the way, that comment about 300 microns ... was that only on a start up of a brand stinking new system?
    Yes. I shoot for 1000 on service, and take more if I can squeeze the time out of the nervous managers....

    Originally posted by R12rules
    What would you pull a circuit down to if you just replaced the coil in a service meat case?
    (leaking ball valves and all)
    The leaking ball valves would get replaced. If they leak, they're useless.

    Then there would be a full pulldown to 1000 or less.

  6. #19
    Join Date
    Dec 2004
    Posts
    46
    Gasngo- I too used only the one belt drive pump at the rack with jumps all over the place. It's difficult to pull from other parts of the system, especially on the sales floor unless special access fittings are installed with ball valves, and most times that's not feasible. Can't pull at the cases through shraders. Often there is access at the heat reclaim coil however. It does take several days to triple evacuate a rack, changing the oil several times. After the first pull, I break with dry nitrogen. I also direct wire the pump to a breaker to avoid the unplugged situation and I have used the solenoid method also. I make up a manifold with ball valves and access fittings and will have 2 or 3 hard piped (thru ball valves again)lines from suction and discharge manifolds and more if there are split suctions. I haven't seen the 150 micros in specs, it's usually 500 to 300 and has to hold in the furthest point in the system I'm sure each chain has different specs

  7. #20
    Join Date
    Jan 2004
    Location
    Earth
    Posts
    4,879
    I always used single pumps 20 CFM or better. Three point evacuation, Suction Discharge, and Liquid. Hard piped and sweat all connections. No less than three days with nitro-breaks every morning. Pump off micron rise readings are the key, to how well your vacuum is doing.

    My spin on Vac-u-seal is, does it turn into pressure-seal when you’re done. If you have a leak fix it now, then you won’t have to later.
    A Diamond is just a piece of coal, that made good under pressure!

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