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School me on double-swing draft regulators

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TomM
TomM Posts: 233
in Gas Heating
Why do they need to swing out?  Sounds dangerous.



-Thanks
beautiful Conshohocken PA

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  • Steamhead
    Steamhead Member Posts: 16,835
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    In NFPA 54

    these are required. The reason is they don't want a down-draft to affect the burner flame or blow out a pilot light. I doubt if any new conversion burners use pilot lights these days, and most of those available can build enough static air pressure to offset a downdraft. Nevertheless, the requirement is still in force.



    The blocked-flue switch will stop the burner if combustion products escape from the double-swing barometric. That's why it is required.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • JStar
    JStar Member Posts: 2,752
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    ...

    It is dangerous, and that's why you should install a backdraft safety on the damper to shut down the system.



    The theory is that if the chimney is ever blocked, the appliance will create less CO by venting directly into the living space than if the draft is reduced so much that the appliance begins to "reburn" the exhaust, or cause a severe flame roll out.
  • TomM
    TomM Posts: 233
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    pilot

    ok, i see, its so the pilot light doesn't go out during an episode of positive pressure.  I didn't think of that. 



    So i guess draft hoods are inherently dangerous because in the event they are blocked, they are not equipped with blocked flue switches.  Is everyone using a double swing w/ blocked vent switch these days on all appliances?



    -Tom
    beautiful Conshohocken PA
  • Steamhead
    Steamhead Member Posts: 16,835
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    Draft hoods

    can be equipped with blocked-flue switches. These are required on new equipment. 
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
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