Repressurizing Heating System

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by chefwong, Nov 7, 2012.

  1. chefwong

    chefwong New Member

    Messages:
    710
    Location:
    District of Columbia
    Hot Water Heating System.
    I've set the stat to 90 degrees - water got hot, pump has been running for about a 1 hr so far.
    When I bleed the lower basement radiators, I am getting water.
    No water on the 1st and 2nd level when I attempt to bleed air.

    Lower basement baseboard are not warm yet.
    When I feel the outgoing / return pipes off the unit and the pump...it's all nice and toasty.

    Any advice.
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,266
    Location:
    New England
    Open the fill valve then open one of the upper floor's bleeder valve until you get water out. Repeat at the other bleeders upstairs. Once you've got all the air out, you should get circulation. It doesn't take much air to block flow when it needs to go up. Once almost all of the air is out, the air extraction system should pull the rest out as it circulates around as microbubbles.

    The pump in most systems doesn't have a lot of head - it takes the full system being full of water with some of it pushing back down to help it flow all the way around. then, since it is a closed system, the low powered pump can keep it flowing.
  3. chefwong

    chefwong New Member

    Messages:
    710
    Location:
    District of Columbia
    Are you saying open all the bleeders and leave them open till water comes out...

    I went around leaving some bleeders open for about 15 minutes....and no dice.
    It's circulating on the *main pipe* as I can feel it hot on the *loop and then the return to the pump*.

    It's just not circulating on the baseboards.
    Even the lowest /closest runs *basement*, water is good coming out the bleeder but they are not getting warm yet.
    I suspect the basement is not getting warm cause the entire *system* is not fully pressureized ?
  4. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,267
    Location:
    Maine
    Not enough water pressure. Your fill valve is probably bad.
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,266
    Location:
    New England
    If you can't get water out of the bleeders, you're not introducing water into the system for some reason. If you have an autofill valve, it may be gunked up, or you have an in-line valve shutting it off (not a bad idea, as once the system is full, it should not be needed to keep it topped off and can mask a slow leak). If things are working right, you should hear air escaping when you open it, and eventually, get water out. You will not get good circulation until you get (nearly) all of the air out. The air extraction devices can only deal with a little air for the most part, not huge amounts.
  6. chefwong

    chefwong New Member

    Messages:
    710
    Location:
    District of Columbia
    Thank you all.

    I did not even check to bleed air prior to restarting today

    I gave a little nudge to the fill valve and some water appeared to flow *heard it flowing*.
    I then cranked up the tstat so it would engage and just went around bleeding air. Amazingly, water was bleeding out almost immediate and I just simply went around bleeding air on all the baseboards.

    The pump was running for another 2+ hrs yesterday before I shut the system down...I did not reattempt to bleed air before I went to sleep.


    BTW, how often or not is one supposed to *empty the water* out of the overflow tank that's on the return side.
    I probably do that that every other year.....
    Last edited: Nov 8, 2012
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,266
    Location:
    New England
    There are a couple of types of expansion tanks. The preferred one is a bladder tank, and on it, you never drain it until it fails. The older styles tend to absorb all of the air and stop functioning, assumig you have an air extraction device. On those, since the air is in contact with the water, a little bit gets disolved as the water goes by, gets extracted, and eventually, stops functioning. Also, since air has oxygen in it, you are constantly adding that to the water which means things can rust. Pure water with no disolved air will not generate rust. When you add water to a system, you're also adding air, and until that gets used up (by rusting things) or extracted (the better choice!) rust continues to accumulate...IOW, you do not want to be adding water to the system or draining things out (which may mean you have to add some water as well). If you're not using a bladder tank, you might want to consider replacing what you have with one properly sized for your system.
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