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Stack damper below draft hood

We see this on commercial water heaters, why not on boilers.  This could be very useful in Modular boilers to cut losses.
The Steam Whisperer (Formerly Boilerpro)

Chicago's Steam Heating Expert





Noisy Radiators are a Cry for Help

Comments

  • Steamhead
    Steamhead Member Posts: 15,256
    The idea

    is to keep the chimney draft from pulling air out of the boiler room via the draft hood, when the boiler is off. This decreases infiltration into the building. I think this also helps keep the chimney from cooling down too much. 
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    Towson, MD, USA
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  • Tim McElwain
    Tim McElwain Member Posts: 4,504
    The closer the damper is

    to the high heat the more likely for motor and electronic failure of the damper. I actually prefer the damper right at the chimney opening,  less heat and better overall control.
  • Losses

    What I am considering is boilers in a commercial boiler room setting where outdoor air is provided and the room is seperated from the heated spaces. In this case the heat that spills from the drafthoods when the damper closes is mostly wasted because it is used for combustion air.  Having the damper below the drafthood would allow the heat to be locked in the casting and not dumped into the room.  I am thinking of this when using modular steamers that are step fired in order to cut the huge standby losses of the extra modules during light loads.  If someone would come up with larger power vent steamer (like the Independence) it would addres this issue even better.
    The Steam Whisperer (Formerly Boilerpro)

    Chicago's Steam Heating Expert





    Noisy Radiators are a Cry for Help
  • Jason_13
    Jason_13 Member Posts: 299
    Draft hood

    The problem with this thought is the height of the draft hood is a certified dimension and cannot be altered. As stated earlier the heat will affect the motor.
  • Tim McElwain
    Tim McElwain Member Posts: 4,504
    The trade off

    as to keeping some temperature in the boiler for transfer to the medium being heated versus the warm air dumping into the boiler room to keep combustion air warmer is what I would question. In very cold times the heating of the incoming air for combustion could be a plus.



    The other issue is that code may not allow you to do this with gas as the diverter (draft hood) is designed to allow products to dump into the room in the case of any failure of the vent damper and firing still allowed to take place it would not have anyplace to dump.
  • Trade off and codes

    With steam modules, the off boilers are constantly being heated by the on boilers, so the loss is constant and very high.  Boiler room temperatures skyrocket when the dampers are above the drafthood... I've measured upwards 110 F and higher.

    As to code, commercial domestic water heaters are already built this way, the damper is below the drafathood, not above.  I really wonder if is a problem, code wise.
    The Steam Whisperer (Formerly Boilerpro)

    Chicago's Steam Heating Expert





    Noisy Radiators are a Cry for Help
  • Height

    I agree the drafthood height would need to stay the same.  The length of the riser pipe would need to be shortened to accomodate the height of the damper assembly or the damper would need to be installed directly in the vent pipe.
    The Steam Whisperer (Formerly Boilerpro)

    Chicago's Steam Heating Expert





    Noisy Radiators are a Cry for Help
  • Height

    I agree the drafthood height would need to stay the same.  The length of the riser pipe would need to be shortened to accomodate the height of the damper assembly or the damper would need to be installed directly in the vent pipe.
    The Steam Whisperer (Formerly Boilerpro)

    Chicago's Steam Heating Expert





    Noisy Radiators are a Cry for Help
  • Tim McElwain
    Tim McElwain Member Posts: 4,504
    Dave, you probably can get

    away with this type hook up on a commercial application as you fall under a different standard. I am not sure however so I would check with local codes and also talk to the manufacturer and see what they say.
This discussion has been closed.