fresh air damper

bklynfrank

I have an 18"x18" duct bringing in fresh air for my steam boiler. I'm thinking of limiting the cold air when the unit is off with a motorized damper. Any suggestions on model or make that has a sensor that will break when it is closed?

Thanks

Abracadabra

I use these.

https://www.grainger.com/category/motorized-dampers/dampers-and-accessories/shutters-dampers-and-louvers/ventilation-equipment-and-supplies/hvac-and-refrigeration/ecatalog/N-ynv?ssf=3&bc=y

SWEI

There should be two openings, one high and one low. Can you post a photo showing the duct termination, boiler, and surrounding area?

bklynfrank

I have only one opening.

SWEI

A single opening up high can provide a certain amount of air for combustion, but it will not allow CO2 (which is always heavier than air) and CO (which becomes heavier than air in cold weather) to escape from the room.

Personally, I will not install a natural draft boiler below ground level without (at a minimum) a double-acting barometric damper and spill switch. Mechanically assisted combustion air would be better, and (if properly designed and installed) will actually reduce net infiltration to the building.