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open gravity system

Buzz G.
Buzz G. Member Posts: 61
is quiet and takes no electricity-those are two pluses that are hard to beat. The major question was going from an open to a closed expansion tank, I suppose you are talking about the amtrol type? These come preset about 12 psi and that is enough for a four-story building (boiler in basement) so you want to cut the pressure down to meet the two-story house needs. I would think about 4 psi would ensure water at each rad. I believe it is around 2.3 ft/psi? So if from the expansion tank to the top of the tallest rad is 10 ft, then you need about 4.3 psi to get up there. It sounds like the HO likes gravity.

Comments

  • Mars_3
    Mars_3 Member Posts: 65
    Open gravity system convert to closed gravity system

    I have an open gravity hot water heating system that I am looking at. 1100 sf ranch cast iron radiators, the mech contractor that came before me installed one Runtal towel warmer and one vertical Runtal radiator. I now need to convert this open system to closed but would like to keep it gravity. My questions are as follows; does the system care where I put the expansion tank, what pressure should the system operate at , do I need to try and install a air separator or should I just fill the system from the coin vents and let her rip. Thanks for any help with these questions.
  • Robert O'Connor_12
    Robert O'Connor_12 Member Posts: 728
    To pump or not to pump?

    Why leave it the way it is? The extra cost to add the circulator is small compared to the money you will save on fuel if you add it.


    Robert O'Connor/NJ
  • Dick Charland
    Dick Charland Member Posts: 178


    It doesn't matter where you place the expansion tank, no need for an air scoop, being a small ranch house, one story you can get away with very low pressure setting. Old rule of thumb height from boiler to radiation divided by two probably puts it in the range of 4 psi or so. I wouldn't add a circulator, these systems are efficient and the only time there is a problem so to speak is the spring and fall. The heat input is based on the thermostat call and with a gradual even heat flowing all the time a well designed and balanced system will run low water temperatures and not use much fuel. Odd to see it in a ranch house, how old is the residence? The more conventional method is constant circulation with a pump and have the thermostat fire the burner. If this is working fine why add electrical expense?
  • Mars_3
    Mars_3 Member Posts: 65
    The home owner likes the gravity system.

    The system was instaled in 1916 as near as we can figure. orignaly coal but converted to nat gas at some point, What the home owner likes most about the system is that is is a millivolt gas valve and on the rare ocurence that we lose power hear in Denver like the storm that just passed last weekend he likes to know he has heat. I canott fault him for this thinking as when we lost power for 5 days straight a couple of years ago I was thinking the same thing. Thank you for your help with my questions. This should be a relativly painless converson.
  • Dick Charland
    Dick Charland Member Posts: 178


    Well there's another benefit to that system.
  • Buzz G.
    Buzz G. Member Posts: 61
    PSI

    should be around 12 PSI at the circulating pump as that apparently is cavitation preventing pressure. Sorry I left that out.
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