School me on double-swing draft regulators

TomM

Why do they need to swing out?  Sounds dangerous.



-Thanks

Steamhead

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.

JStar

...

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

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

Steamhead

Draft hoods

can be equipped with blocked-flue switches. These are required on new equipment.