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Thread: Replacing tank on vfd

  1. #1
    DIY Junior Member greenmonster304's Avatar
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    Default Replacing tank on vfd

    The tank for my vfd started to leak so I want to replace it but I am not sure what pressure to charge the new tank to. I wasnt sure if the vfd tanks get charged differently. Thanks in advance for your help.

  2. #2
    Moderator valveman's Avatar
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    The tank precharge is usually about 30% less than the running pressure.

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    DIY Junior Member JPat's Avatar
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    Hmmm. Every VFD we have installed, the manufacturer recommends 70% air pressure to running pressure...Doing the math for you; if your running pressure is 60psi the pre-charge in the tank should be 42psi.

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    Moderator valveman's Avatar
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    Hi JPat. Doing the math I think 70% of, or 30% less than 60 is still the same 42 PSI. The real question is why did the tank go bad?

  5. #5
    DIY Junior Member JPat's Avatar
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    Meh, tanks go bad all the time. The rubber that most companies are using is recycled... "Do it yourself" tanks have a high failure rate as well. 5yr warranty on all tanks!!!

  6. #6
    Moderator valveman's Avatar
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    Bladder or diaphragm type tanks only go bad for two reasons. Either they rust through, or the bladder breaks. Most of the busted bladders I see on tanks with a VFD, are from the pump not shutting off when it should, causing the pressure to spike and bust the bladder.

    One of the big box stores has a 32 gallon tank with a lifetime warranty. I guess it doesn’t have recycled rubber.

  7. #7
    In the Trades Texas Wellman's Avatar
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    "Lifetime warranty"...when it breaks, the life is over!!

  8. #8
    DIY Junior Member greenmonster304's Avatar
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    The tank rusted out because it was in a pit that was always damp.

  9. #9
    Moderator valveman's Avatar
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    Quote Originally Posted by greenmonster304 View Post
    The tank rusted out because it was in a pit that was always damp.
    Good to know. These are the kind of installations that can benefit from a fiberglass tank.

    Yeah "lifetime warranty". Can you believe that? I think the company might just change names every few years to get out of warranties.

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