Indoor wood furnace duct help

[vipertec]

I am installing a new gas furnace in basement with duct work. Also have a Harmon sf3500 wood furnace I want to use. My question is can I tie the wood furnace into the duct work that is fiber board not metal?I was planning to use metal over to the fiber duct

 

[moresnow]

@brenndatomu

Opinion request

 

[vipertec]

I tried to contact Harmon and I can never actually get anyone on phone to give me any info,only email and they don’t give me any answers

@brenndatomu

Opinion request

@brenndatomu

Opinion request

Not sure what that means?

 

[moresnow]

I tried to contact Harmon and I can never actually get anyone on phone to give me any info,only email and they don’t give me any answers


Not sure what that means?

I am requesting that members advice for you. He has some background with these systems.

 

[brenndatomu]

My question is can I tie the wood furnace into the duct work that is fiber board not metal?I was planning to use metal over to the fiber duct

No, wood and or coal furnaces are required to have all metal duct...and it needs to meet required clearance to combustibles (CTC) too...not sure if you have that info for your Harmon furnace or not. If not, many require 6" at the plenum and for the first 10', then somewhere's between 1 and 2" for the remainder of the system...obviously by the time you get to the registers that will not be possible.
Wait a minute, is this a pellet furnace?
If so, the requirements I listed may be wrong...

 

[brenndatomu]

Doesn't look like the owners manual is much help either...
http://downloads.hearthnhome.com/installmanuals/sf1500a_2500a_2600a_3500a.pdf

 

[vipertec]

No, wood and or coal furnaces are required to have all metal duct...and it needs to meet required clearance to combustibles (CTC) too...not sure if you have that info for your Harmon furnace or not. If not, many require 6" at the plenum and for the first 10', then somewhere's between 1 and 2" for the remainder of the system...obviously by the time you get to the registers that will not be possible.
Wait a minute, is this a pellet furnace?
If so, the requirements I listed may be wrong...

No,it’s wood.

 

[brenndatomu]

OK, then the requirements I listed will be exactly (or very close) to what they would spec out...metal duct for sure.

 

[Ikeholt]

I hired a pro to do the ductwork on my wood furnace 26 years ago. He used the insulated, non metallic type. Temp of the hot air is the same as a gas furnace, so I'm not sure why it would matter. But maybe today's code is different.

 

[vipertec]

OK, then the requirements I listed will be exactly (or very close) to what they would spec out...metal duct for sure.

Can the take offs be insulated flex or do they have to be metal also. Thanks for the info in advance.how much higher are the temps from wood furnace over propane furnace?

 

[brenndatomu]

Needs to be all metal.
The normal operating temp of the ducts would (or could) be similar to a gas or oil furnace...that's not the issue...the issue is when the power fails (or other system failure) the fire does not go out as with a fossil fuel burner...things can get VERY hot.
I just talked with a fellow that had a power failure at the worst possible time...right at the hottest point of the burn (hour or two in) and even though the intake damper closed, the pilot air allowed the the fire to continue on and things got so hot that the plenum connector area (above the furnace) that is painted with high temp paint and has some warning/safety stickers (metallic "high temp" type decals) blistered up/discolored!

I hired a pro to do the ductwork on my wood furnace 26 years ago. He used the insulated, non metallic type. Temp of the hot air is the same as a gas furnace, so I'm not sure why it would matter. But maybe today's code is different.

Typical...most HVAC people don't have a clue (and don't give a crap) about wood or coal heat...and don't care to learn.
Code is for all metal...has been for a long time...would have been considered "best practice" before any code requirements too.

If this was a pellet furnace, then I believe you would be OK with some nonmetallic duct due to the fact that there are safety switches that can stop the fire, basically when the power goes out, the fire goes out.