expansion tank on loop field

Discussion in 'Geothermal Loops' started by Calladrilling, Mar 14, 2012.

  1. Calladrilling

    Calladrilling Member Industry Professional Forum Leader

    I got a drawing for a system we are to be installing soon. It is a larger sized residential closed loop (7.5 ton). The HVAC contractors drawings are showing a expansion tank on the supply line before the pump. I know its purpose but is it really needed for residential? When I flush/purge loop field and heater, I can add pressure to field through flush cart.
  2. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    Submit a RFI (request for information)

    Follow that with a (request for change order)

    Amend your scope of work and schedule of values

    Nothing is really necessary except "death and taxes"
  3. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    We have employed pressure tanks in some large resi applications where multi HP circulators are employed.
    While not completely necessary, different things may make it useful i.e. PSC pumps vs variable, mixed materials and threaded joints such as plactic to metal etc.
    The pressure tank can be useful to avoid flexing that might cause leaks in threaded joints or torque that can cause material fatigue.
    Might also be a great place for a QT.
    Careful when flushing.
  4. zacmobile

    zacmobile Guest

    expansion tanks

    I have been including expansion tanks on every one of our loops for the past 6 years, imo every closed pressurized system needs one. I have seen so many older systems with pressure fluctuation problems that at first glance seemed like a leak in the loop but was just due to there being no room for fluid expansion/contraction from temperature changes. It is not a major expense at all and it can save a lot of headaches so why not?
  5. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    Most of the residential systems install manuals from manufactureres identify that this expansion and contraction is the function of the "hose kit". In the absence of a hose kit a expansion tank may be prudent.

    We never employ them in residential installs. There are installers in my area that install a expansion tank, water make up, and air snifters in residential systems. It is not wrong, but is expensive.

  6. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    I agree with Zacmobile

    Take a look at the Caleffi site and read Idronics #9.

  7. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    Why not using a non pressurized flow center and call it a day?
  8. zacmobile

    zacmobile Guest

    I've been a little disillusioned with non-pressurized as of late, you have to use a whole whack of brass tees & valves for flushing when you get the same benefits by simply installing an expansion tank. I have tried air separators before but if you have a good flush cart with air screens & do a good job of purging on commissioning it is pretty redundant.

    @waterpirate: I would venture to say that having a water make up on a closed loop antifreezed system is wrong, if a major leak ever developed you run the risk of dilution to the danger point. Same as a solar system, if make up is a requirement a glycol feeder would be the name of the game.
  9. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    I have to say I am not smitten with the nonpressurized flow center leaving so much of the valving to us. Nor am I thrilled with the price. With what we can get a pressurized flow center for, the difference going to a QT is easily $400.
    That has always been a no brainer for me.
    The problem is Doc is such a fan of the things and I respect Doc's opinions so I've had to try to wrap my head around the benefit(s) again.
  10. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    I'm stuck in the middle

    Started with non-pressurized. Switched to pressurized. And now we're making the transition back to non-pressurized.

    And they are a headache. Just try to have nice looking plumbing...

    Anyway, there are a few reasons we're going back based on experience:
    - I can order just the "shell" and put in whatever pumps I want
    - Less call backs (for whatever the reasons may be, it just is)
    - Easier servicing when we do get a callback

    So, basically, I'm flexible:) Not convinced either way.
  11. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    Doc, I sorta hoped you'd jum in after my last post.....
  12. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    Traveling in Europe right now.

    Non-pressurized are called call back eliminators.

    Water contains dissolved gases, for example Oxygen. Keep it under pressure and they stay dissolved. However, in the A/C mode the warmed pipe expands, resulting in a drop in pressure. The gases participate out and form micro bubbles, requiring sometimes re-purging. The canister of the flowcenter purges them out automatically.

    We have Phoenix Energy Supply make custom PE fitting for the purge ports. Standard on all our installs. See cut sheet attached.

    Attached Files:

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