Reverse damper

Getwidit

New Member
Aug 28, 2019
26
Stuyvesant ny
I had a brain fart a backdraft damper for my furnace plenum. So I can run my wood stove with out it back drafting through the furnace.. but then my furnace can kick on it need be with out my manually changing a damper.
 

brenndatomu

Minister of Fire
Aug 21, 2013
4,148
NE Ohio
Ahh, OK...well, it really depends on your system...you might be able to get away with using a couple "swinging door" type dampers, those can be homemade, or a local tin shop could do it reasonably too I'm sure...not much to it.
Or, what I did was to install an auto damper...spring loaded to be open when the power fails so that the Kuuma can still cool itself by gravity heating...fortunately my house was originally coal heat so the ducts all have some rise on the runs to allow for gravity heating. Actually, I have a swinging door gravity damper door on my FO furnace to keep the Kuuma from backdrafting into the FO, then the auto damper is on the return air drop leg of the Kuuma to keep the FO from "short circuiting" when it runs...like I said, the damper is open all the time unless the FO heat, or central air is running.
If you go the auto damper route, don't cheap out...here is what you want.
https://www.retrozone.com/Catalog/Rectangle Dampers /3085.htm
The 3085 SD damper, with Belimo actuator...it will cost you $50-$75 or so more than other brands/models that you can get, but you will not have to ever fool with it again...Belimo is the best. Have the lowest amp draw, and are field reversible too...as I said before mine is set to be open on power failure, but your system might need closed on power fail...you can just turn the Belimo around and good to go...can't do that on other brands. If you have questions, call these guys and talk to Jerry, he really knows his stuff!
 
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Getwidit

New Member
Aug 28, 2019
26
Stuyvesant ny
I just need to keep my wood stove from pushing backwards through my ducts.

What do u mean by ur kuuma is short circuits ur fo furnace. (FO just means ur normal furnace)?
 

brenndatomu

Minister of Fire
Aug 21, 2013
4,148
NE Ohio
I just need to keep my wood stove from pushing backwards through my ducts.
Right...that's what I'm talking about.
What do u mean by ur kuuma is short circuits ur fo furnace. (FO just means ur normal furnace)?
If I didn't have the damper on the return air drop leg of the Kuuma, my fuel oil (FO) furnace would blow backwards through the return leg and "short circuit" back to itself...instead of pushing the air through the supply ducts to the house...one detail I forgot to mention that may be confusing is that the Kuuma is set up as "the main furnace" as far as how the ducts are run...the FO is almost an add on. The FO supply plenum is tied into the supply plenum of the Kuuma...they each have their own separate connection to the main return air duct
 
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Getwidit

New Member
Aug 28, 2019
26
Stuyvesant ny
Okay I understand better now I dont see myself needing that auto damper then.. that's what you use it on correct ur kuuma side. I don't envision myself needing anything electronic related on this project. Just simply a gravity system.
 

brenndatomu

Minister of Fire
Aug 21, 2013
4,148
NE Ohio
Yes, on the Kuuma side...Lamppa MFG recommends a gravity damper system, but with what I was working with, it just wasn't gonna work out...plus I wanted the Kuuma to be able to gravity heat on power loss...no way of making that happen with only gravity dampers in my system...I had very limited options due to space/etc. It was a minor miracle that things worked out the way they did...there were countless places where things cleared, but just barely! And CTC specs were met too...whew! I need to post an install thread with pics I guess...
 
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brenndatomu

Minister of Fire
Aug 21, 2013
4,148
NE Ohio
Here is what Lamppa recommends...there are lots of variations of this out there from different company's
This is basically what I have done, only the wood and the oil furnaces would be switched in this illustration...that and I have an auto damper on the return side instead of a gravity flapper...
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