Englander Wood Furnace - tying into existing HVAC duct

[6t6cuda]

First time poster, long time reader...

After much research I just bougth a
Englander
Model # 28-3500
3,000 sq. ft. Wood-Burning Add-On Furnace

From Home Depot (site to store) - it should be here in the next week or so.

I am just sketching out the "plumbing", I have an existing wood stove which exhausts into a masonry flu, I think that will be easy to work with, but the question is how to tie into the existing heating duct work.

The existing stove is in the basement at one side of the house the main (heat pump / electric) HVAC is in the center of the house. I have a HVAC "feed" which I could tie in easily from the Englander, but I am worried that it might not feed the entire house.

So the question is am I better "directly" tying into the end of the trunk line near the Englander, or should I run 8" solid metal pipe all the way back to the main feed point of the exiting HVAC system? I assume it would be better to insulate this pipe as the run might be 25 ft total leading to the existing trunk.

So what is better having a "short" 10 ft run and tying into the end of the trunk or running all the way back to the main split of the trunk near the existing HVAC system?

THANKS IN ADVANCE!

 

[Wisneaky]

Tie it in as close as possible. Don't run it back. Also I wouldn't insulate the duct with a wood furnace. They get too hot for that.

Also make sure you are following the manufacture recommended clearance to combustibles for the duct work. It's usually so many inches for so many feet.

 

[rkusek]

the 25ft of 8" round would very restrictive. Doesn't the furnace have two 8" outlets? Most people have like a manual damper or spring loaded or electrically actuated damper to prevent one furnace from back feeding into the other when they are tied into the same duct work. My FIL has a manual one so it's either wood or heat pump. You probably want a setup where the heat pump kicks in when the wood dies out and the house cools a few degrees.

 

[6t6cuda]

I was plannning / have on order a backdraft damper: http://www.homedepot.com/p/Speedi-P...8+in.+Galvanized+Back+Draft+Prevention+Damper

This is suggested per the mfg to prevent the normal HVAC from feeding back into the Englander.

Also, the Englander only has one 8" pipe to tie in; I know most others have two, but this unit is physically smaller and only has one.

Thanks!

 

[Wisneaky]

I was plannning / have on order a backdraft damper: http://www.homedepot.com/p/Speedi-Products-8-in-Galvanized-Back-Draft-Prevention-Damper-AC-BD-08/202907128?keyword=8 in. Galvanized Back Draft Prevention Damper

This is suggested per the mfg to prevent the normal HVAC from feeding back into the Englander.

Also, the Englander only has one 8" pipe to tie in; I know most others have two, but this unit is physically smaller and only has one.

Thanks!

You should also install a back draft damper in your primary furnace plenum.

 

[lexybird]

When I had one I enlarged the single 8" duct hole to a 10" and ran 10" ducting instead . Worked wonders moving more air. They are not made to have return air and without a filter system of some kind I think dust would cause issues