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(pix) Is this correct? Exhaust on Steam Boiler passing air 24x7 in winter?

davevarga Member Posts: 44
Big Heat Loss through steam boiler vent?

I have a 1920 built house with steam heat (one pipe).

It just occured to me that during the winter, even when the boiler is off, relatively warm basement air is racing up the chimney  through the boiler exhaust vent 24x7, even when the boiler is not cycled on. Is this right? If so, this is a big loss of heat in the basement.  Is there anything I can do about shutting off this exhaust vent until when the boiler cycles on?  Also I notice on the bottom of the rectangular box (in the picture), it is open, is that normal?

See pictures on this link:

<a href="http://www.netdevi.com/hse/steamboiler.htm">[url=http://www.netdevi.com/hse/steamboiler.htm]http://www.netdevi.com/hse/steamboiler.htm</a>

Thank you...!



  • Steamhead
    Steamhead Member Posts: 16,237
    Yes, it's a huge waste

    your chimney was designed to pull air thru a bed of coal in the original boiler. This strong draft is much more than a gas or oil-fired boiler needs.

    If the boiler has a dual-seated gas valve, an electric stack damper may be installed above the draft hood (box) and properly wired into the control system. If it does not, the gas valve will have to be replaced also. There has been some controversy regarding how much these dampers actually save, but in your case it's pretty much a no-brainer.

    This is NOT a do-it-yourself job. Do not attempt to do this yourself. The installation MUST be made by a qualified professional who knows how to make it work safely.

    You can find one on the Find a Professional page of this site.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • Tim McElwain
    Tim McElwain Member Posts: 4,593
    That big box on the back of the boiler is the draft hood and it has

    to be there in order for the system to vent properly. You could however have a vent damper installed which will close off when the system is satisfied reducing your standby losses up the chimney. Do you have a standing pilot on this boiler?
  • boiler flue damper?

    i would also be concerned about whether you have enough height in the steam main above the waterline [needs 24 in.]. does the system heat properly?  any water-hammer in the hartford loop?--nbc
  • davevarga
    davevarga Member Posts: 44
    exhaust on the Steam boiler

    I think it heats the house fine, there is no hammer. I've been here five years, if there is a loss of efficiency because the steam main vertical is less than 24", I do not know definately about that.
  • davevarga
    davevarga Member Posts: 44
    Exhaust on Steam Boiler

    Yes it is a standing pilot light, it is always on.
  • davevarga
    davevarga Member Posts: 44
    Exhaust on Steam Boiler


    When you say it is a no brainer, you mean not that it is easy to do because you say a professional must do it, but that it would save standby losses for sure?

    I'll find out about the gas valve. Thank you very much.
  • davevarga
    davevarga Member Posts: 44
    huge waste

    Got it, huge waste... thx!
  • Tim McElwain
    Tim McElwain Member Posts: 4,593
    The reason

    I asked about the standing pilot is to make sure if you have a vent damper installed to remove the knockout in the blade so the products of combustion from the pilot can vent when the damper is closed.

    You will also need to make sure that a blocked vent switch (spill switch) is installed.

    Now what is the make and number on the gas valve? This is so I can determine if you will also need to change the gas valve as it must be a dual seated (redundant) valve.
  • davevarga
    davevarga Member Posts: 44
    Gas Valve on my boiler


    Sorry for the delay, just saw your post...

    The furnace is a weil mclain EG series, not sure the size, I think it was installed in the 90's.

    Here is a link to the pictures, I added the gas valve pictures at the bottom of the pages along with some identifying numbers, I doubt if they are model numbers of the boiler and the valve.


  • Tim McElwain
    Tim McElwain Member Posts: 4,593
    The gas valve is a

    single seated valve which means that if you go with a vent damper it will have to be replaced. From the pictures it looks like your boiler could use some service and a good cleaning. At the same time have a combustion analysis done. I would also clean up the wiring to get wires out of the combustion zone.

    I would have a professional heating contractor come and take a look at your boiler and advise you. Ask them if they do combustion testing and boiler tune ups, if they say no then do not have them come.
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