Damper question.

[Iaff113]

I am in the process of building and outdoor forced air furnace out of a Hotblast 1557m. My question is. Where should I put a damper in? I will have about 10 feet of triple wall chimney pipe. I can't seem to find any thing online about an add in piece. Or does anyone have any other ideas to prevent an over fire if the blowers fail

 

[brenndatomu]

You probably don't need a damper on a 10' chimney, not much draw there.
What does blower failure have to do with the damper anyways?

 

[Iaff113]

I have read a lot on possible over fire. If you have a blower failure or power outage because their is no movement of air around the fire box. So I was trying to think of a way to dampen it down if that happens.

 

[brenndatomu]

You need a limit switch wired in for the intake damper or combustion blower...supply plenum too hot, limit cuts the power to the intake, fire dies down.
Pretty typical setup on any forced air furnace. Look in the manual for the furnace, they should show a limit switch in the diagram. Most have a Honeywell that controls the blower on n off and also cuts power to the intake on overheat

 

[Iaff113]

Well that's the other issue that seems to have a ton of issues. Or atleast that's what I have read. I have completely blocked off the regular intake. I can easily return it to normal if I have to. So I guess if a power outage happens. I'll just shut off the ash door damper and monitor it just to see how hot it gets.

 

[NSMaple1]

I have completely blocked off the regular intake.

Why?

 

[Iaff113]

I put a plate on the adjuster because everything I read said it was hard to control the burn from the adjustment. They were all saying that the best way was to adjust the intake draft from the ash pan draft knob

 

[brenndatomu]

everything I read said it was hard to control the burn from the adjustment.

True dat

 

[Iaff113]

So should I not worry about trying to order a damper untill I have Afew burns in it

 

[NSMaple1]

I just caught the outdoor furnace part. That is going to burn a LOT of wood, likely with not a lot of the heat output making it to the house. Plus you might not have the natural convection upflow you would have with a typical install to deal with shedding heat in a power outage. Although we don't know exactly the layout your planning...

 

[Iaff113]

Yeah wood isn't an issue so I'm not worried about that. I knew going into it that it is a wood eater, heat loss through the duct won't be that bad because it will be a small run and will be insulated, it will have 16 feet of triple wall chimney so I don't know about the heat shedding