Wood/oil burner duct servo?

[Midniteoyl]

The simple butterfly type or spring loaded backdraft dampers work and are cheap, assuming two air handlers which is what i think you described...

But, if you have rectangular ducting, and the oil burner comes in vertically from the bottom, a simple flapper valve placed over the duct angling in would do the same. A simple piece of sheet metal covering the entrance, hinged in the rear. When the air from the oil burner is moving through it, it will be pushed 'up', when not, it will fall back down due to gravity. You can line the flapper with foam to seal and quiet it... Simple.

If the duct comes in hortizonally, a very light spring could take the place of gravity, though prolly not needed as the pressure would 'hold' it shut.


edit: picture to give idea, though I would make the flapper big enough to touch the other side of the dict at an angle so as to not worry about it 'making a seal' against the other hole.

 

[hr3]

Chopped ,, How did your duct work and damper work out??? I have an add on wood furnace too and love it,, 20 below outside last night and nice and warm this morning inside,,

 

[chopped]

Well i bought two of these.
Johnson Controls M9210 Bac 3 Spring Return Damper Actuator 120V w Switches | eBay
Very Heavy Duty.. Haven't gotten them installed quite yet but I tested them and they work fine. I have a wood furnace and also an oil furnace into the same hot air trunk.And for 30 years have had to manually turn on and off the dampers.These will allow them to work independently .I plan to wire them each into the blower fan circuit so they will open and spring closed with the fan on and off.On the oil it wont cycle to often as it tends to blow pretty steady. but the wood/coal furnace it will usually cycle (blow) many times.So i hope the modual lasts. But for this price I think it will . Only time will tell.
I had a 'woodchuck' furnace new in 1980 and it worked fine but didnt have the fan on the intake.so it was alot of tending to it.
In 1985 I bought a NEW woodfurnace for 200 bucks.:thumbsup::thumbsup:9it was one someone bought in panic in the original energy crisis)(1970's).It is a slight bit undersized for my house but I began using that one 15 years ago. and has worked fine for me. the original i sold ..
Wish i still had it back.
Anyways the damper mods are well worth the money. I saw a few that were smaller, and I liked them but I would have had to get a transformer and the price would come close to what I paid for these.(120 volt)..

 

[chopped]

Thanks everyone for the thoughts. Im enclosing a couple of pictures as I get the damper installed..
:thumbsup: