Overwhelming!!! Want an add-on wood furnace...

wallyblackburn

New Member
Aug 14, 2019
3
Central OH
I literally laid awake last night mulling over options for alternative/backup heating. Given that I'm sleep-deprived and this is my first post, please be gentle if I ask something stupid. I have read many, many posts on the forums here, but I am simply overwhelmed. Would really appreciate any wisdom...

I have a 1400 sq. ft. ranch that was built in 1959, but gutted and remodeled about 5 years ago. Good windows, good insulation. On 6 acres of woods out in country a bit. But, I am fortunate to have natural gas heat! With NG hot water, stove, furnace AND radiant in my 34x46 shop, my bill has never hit $300 on even coldest month. So, I really don't *need* wood heat. I would just like for emergency backup and occasional supplementing.

I have a masonry chimney with 3 clay-lined flues. It appears to be concrete block all the way to top with decorative stone where exposed. One flue is for fireplace on main floor, one is for a fireplace in the basement (yes, in the basement) that has never been fired. And one is for the original oil furnace and is no longer used (HE furnace now vents via PVC).

Based on location, I would like to use the old oil-furnace flue to vent a 50-SHW40. The inside dimensions of that flue are 6.5" x 10.5" and it is 18'8" from top of clay liner to where it would have to go 90 degrees and about 5' to attach to furnace. I have seen, read, everything from stub a pipe into the flue and be done with it to an insulated liner all the way. I do have what seems like a reputable chimney outfit coming on 8/29 to do video inspection - figured I'd get advice and estimates from them. But, I'm guessing they will want more than I'm willing to spend - we'll see.

Do I need an insulated liner? I don't think I could get anything bigger than 5" - if that.

Just a 6" stainless flex liner? It would be tight - but seems I could get it through that flue - or am I dreaming?

Any insight greatly appreciated!

Thanks,
Wally
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
19,149
central pa
I literally laid awake last night mulling over options for alternative/backup heating. Given that I'm sleep-deprived and this is my first post, please be gentle if I ask something stupid. I have read many, many posts on the forums here, but I am simply overwhelmed. Would really appreciate any wisdom...

I have a 1400 sq. ft. ranch that was built in 1959, but gutted and remodeled about 5 years ago. Good windows, good insulation. On 6 acres of woods out in country a bit. But, I am fortunate to have natural gas heat! With NG hot water, stove, furnace AND radiant in my 34x46 shop, my bill has never hit $300 on even coldest month. So, I really don't *need* wood heat. I would just like for emergency backup and occasional supplementing.

I have a masonry chimney with 3 clay-lined flues. It appears to be concrete block all the way to top with decorative stone where exposed. One flue is for fireplace on main floor, one is for a fireplace in the basement (yes, in the basement) that has never been fired. And one is for the original oil furnace and is no longer used (HE furnace now vents via PVC).

Based on location, I would like to use the old oil-furnace flue to vent a 50-SHW40. The inside dimensions of that flue are 6.5" x 10.5" and it is 18'8" from top of clay liner to where it would have to go 90 degrees and about 5' to attach to furnace. I have seen, read, everything from stub a pipe into the flue and be done with it to an insulated liner all the way. I do have what seems like a reputable chimney outfit coming on 8/29 to do video inspection - figured I'd get advice and estimates from them. But, I'm guessing they will want more than I'm willing to spend - we'll see.

Do I need an insulated liner? I don't think I could get anything bigger than 5" - if that.

Just a 6" stainless flex liner? It would be tight - but seems I could get it through that flue - or am I dreaming?

Any insight greatly appreciated!

Thanks,
Wally
To fit an insulated liner in there you would need to either go with an oval liner or remove the clay liners. And yes you want an insulated liner. In most cases it is required by code and even if it isn't required the benefits in performance are worth it.
 

blades

Minister of Fire
Nov 23, 2008
3,335
WI, Leroy
Englander Stove - wood furnace
 

brenndatomu

Minister of Fire
Aug 21, 2013
4,259
NE Ohio
What is a 50-SHW40?
Its basically the famous NC30 wood stove made into a wood furnace by adding a jacket and large blower to it...They seem to work fine if you don't mind the manual control of the fire (no thermostat hookup)
 

blades

Minister of Fire
Nov 23, 2008
3,335
WI, Leroy
no thermostat because it is not a draft induced unit ( combustion air blower)
 
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Mrpelletburner

Minister of Fire
Jan 20, 2011
561
N.H.
I am no expert... but as long as you have the correct clearances, you should not need an insulated SS liner. I have a non insulated SS 6” liner, outside wall stack, ~32’ tall with no draft issues.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
19,149
central pa
I am no expert... but as long as you have the correct clearances, you should not need an insulated SS liner. I have a non insulated SS 6” liner, outside wall stack, ~32’ tall with no draft issues.
Yes but very few chimneys have required clearances. And as far as performance uninsulated does work. But insulated works much better.
 
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brenndatomu

Minister of Fire
Aug 21, 2013
4,259
NE Ohio
Yes but very few chimneys have required clearances. And as far as performance uninsulated does work. But insulated works much better.
This ^ ^ ^.
Plus you can get away with things with a 32' chimney that won't work at all with a shorter chimney...
 
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brenndatomu

Minister of Fire
Aug 21, 2013
4,259
NE Ohio
no thermostat because it is not a draft induced unit ( combustion air blower)
All of the PSG/SBI wood furnaces are natural draft, and have Tstat hookup...
 

Highbeam

Minister of Fire
Dec 28, 2006
16,366
Mt. Rainier Foothills, WA
All of the PSG/SBI wood furnaces are natural draft, and have Tstat hookup...
Right, I think no thermostat because the draft control is all manual. No overheat protection either!

The furnace manual may allow for hookup to your clay lined chimney. If so, it should also specify the maximum allowable size.

Insulated liners are best but not always required.
 

wallyblackburn

New Member
Aug 14, 2019
3
Central OH
Thanks for all the replies, folks. At this point, I'm going to wait for the inspection on 8/29 and get advice from the chimney sweep.

Here is what I *think* understand based on what I've learned here and elsewhere:

- Insulated liner would be safest and most efficient (duh)
- A non-insulated liner COULD work and meet code if the clay liner is in good condition AND the chimney has proper clearances (slim chance)

Don't know how much this means, but the chimney was inspected by the building inspector during the remodel. They required some sort of fire-resistant foam insulation to be put in a few places.

Now, to veer off into the weeds just a bit: The manual for the stove *does* say that it can be vented into a masonry chimney. If the clay liner is in good condition - and given that this will see only occasional use - could this be adequate for my emergency backup needs? I think I'm understanding that the big risk is a chimney fire that leads to a structure fire. With occasional use and regular inspection and sweeping, is it doable?

Thanks,
Wally
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
19,149
central pa
Thanks for all the replies, folks. At this point, I'm going to wait for the inspection on 8/29 and get advice from the chimney sweep.

Here is what I *think* understand based on what I've learned here and elsewhere:

- Insulated liner would be safest and most efficient (duh)
- A non-insulated liner COULD work and meet code if the clay liner is in good condition AND the chimney has proper clearances (slim chance)

Don't know how much this means, but the chimney was inspected by the building inspector during the remodel. They required some sort of fire-resistant foam insulation to be put in a few places.

Now, to veer off into the weeds just a bit: The manual for the stove *does* say that it can be vented into a masonry chimney. If the clay liner is in good condition - and given that this will see only occasional use - could this be adequate for my emergency backup needs? I think I'm understanding that the big risk is a chimney fire that leads to a structure fire. With occasional use and regular inspection and sweeping, is it doable?

Thanks,
Wally
Ok the condition of the clay liner doesn't effect the insulation requirements. That comes down to clearances. Do you have combustible materials touching the outside of the masonry chimney structure? That includes the firestop foam. That is not fire resistant it just stops airflow slowing the spread of fire.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
19,149
central pa
And yes if you have required clearances and the clay liners and their mortar joints are in good shape you can run it that way.

Is this an interior or exterior chimney?
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
19,149
central pa
It is an interior chimney.
In that case you need 2" clearance to combustibles from the outside of the masonry structure to anything flammable. Without that you need an insulated liner.