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  1. #1
    Join Date
    May 2010
    Location
    Canada
    Posts
    900

    Very easy question on expansion tanks

    This is still site unseen for me so bear with me......

    When charging an expansion tank (non-diaphragm) I always thought all you have to do is drain it completely and refill it so there is a cushion of air? A tech at my work says he has to pressurize it with a bike pump. I have never heard of doing this but wanted to check here before I put a stop to this. I told him that for a diaphragm tank but he said you can do it with a non-diaphragm as well???

    Its on a closed loop water tower if that matters at all.

    The tank has no rating plate or anything on it.

  2. #2
    Join Date
    Feb 2010
    Location
    Ontario Canada
    Posts
    1,341
    Drain completely and re-fill.....This is the way I have always done it with a non-diaphragm tank.
    Never give up; Never surrender!

  3. #3
    Join Date
    May 2010
    Location
    Canada
    Posts
    900
    Quote Originally Posted by trouble time View Post
    Drain completely and re-fill.....This is the way I have always done it with a non-diaphragm tank.
    Thats what I thought.

    How do I determine what the air pressure should be in the tank?

  4. #4
    Lets remember that volume varies indirectly with pressure. If your pressure goes up, your volume goes down. If you have a non diaphragm tank and you pressurize it to say 14.7 PSI, and your pump is only at 13 PSI, then the tank might as well not be there and you run the possibility of going through pump seals and having constant pressure issues. Is this an evaporative loop for water source heat pumps?. If you drain it and refill it to about 2/3 filling the sight glass with the pump off, you should be golden! FYI, reason for needing to pressurize your bladder tank is because imagine down hill bicycling with flat tires... no bueno! You need some cushion for the pushen man! Good luck buddy

  5. #5
    Join Date
    May 2010
    Location
    Canada
    Posts
    900
    Quote Originally Posted by louiscausley View Post
    Lets remember that volume varies indirectly with pressure. If your pressure goes up, your volume goes down. If you have a non diaphragm tank and you pressurize it to say 14.7 PSI, and your pump is only at 13 PSI, then the tank might as well not be there and you run the possibility of going through pump seals and having constant pressure issues. Is this an evaporative loop for water source heat pumps?. If you drain it and refill it to about 2/3 filling the sight glass with the pump off, you should be golden! FYI, reason for needing to pressurize your bladder tank is because imagine down hill bicycling with flat tires... no bueno! You need some cushion for the pushen man! Good luck buddy
    Yeah it's an evaporative loop for heat pumps. The sightglass method is the only one I have ever used on a non-bladder tank. Thanks for the help!

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