Basement wood stove replacement

[ccanfield]

Hi All, First time posting, long time lurker! We purchased a house in July that has a Harman Mark 2 installed in the finished basement. The house is a ranch-style home with approximately 2,000 square feet, including the basement. 7-foot ceilings downstairs, 8-foot upstairs. The house was remodeled about 8 years ago with good insulation and windows.
The previous owner was using the Harman as a wood burner, and had fabricated an air exchange system surrounding the stove and pushing air through the HVAC vents upstairs. We've been using the stove as primary heat, still burning wood ( I know it's a coal stove), and have been using wood much faster than we should be this time of year. The stove will get us through this winter, but I would like to replace it with a dedicated wood burner, remove the HVAC and probably utilize passive flow. Chimney thimble exits through the basement wall with an exterior chimney on the south side of the house.
My question is, with just a staircase and passive air exchange would something like a Osburn 2,000 be big enough to keep the temps in the house comfortable enough? We're content right now around 70-72 degrees but would be fine if it got warmer in the house. I'm open to catalytic stoves as well, but because we use the downstairs as a living room/rec area, we like the aesthetic appeal of a secondary burn with actual flames. We are in central PA, with access to good seasoned wood. This year I'm burning a mix of oak, beach and maple that was cut standing dead, and seasoned two years. I had to move three cord when we moved from our old house!

 

[begreen]

One option would be a wood furnace. Some of these have a decent secondary burn system inside.

For a woodstove, can we assume that the basement walls are insulated? Is the basement ceiling insulated or not?

If you can, post a sketch of the layout per floor that includes the stairwell and wood stove locations. Pictures of the current setup could also be helpful.

 

[ccanfield]

Yep basement walls are insulated with the exception of behind the stove. Ceiling is not insulated, and we currently get really nice radiant heat through the floor. I've added a basic layout of the house and pictures of the setup. Basement is almost completely open except for a bathroom and small storage closet that I omitted where the water softener is. We always keep the stairwell door open for our cats to get downstairs and for the dog to clean up the cat food.

 

[stoveliker]

I am heating a 1700 sqft + 825 sqft basement with a basement stove with a slightly larger firebox (2.9 cu ft vs 2.4 for the Osburn). Insulated basement (and rim joists!), R13 in the walls upstairs, excellent quality windows, and R57 in the attic.

But the Osburn likely has a larger heat output (than my cat stove) - meaning I think you'll be fine with that size stove in that size house, but you'll have to reload a bit more often than I do. (Last night it was howling and 17 F, and I got 11 hours out of my load of red oak).

Regarding passive heat transport, that works best if you have a circuit of air, i.e. stairs heat going up and elsewhere colder air coming down.

In my experience (but others may have a different experience), doing this passively is hard.
I did it actively - but not by pushing warm air up, but by sucking cold air from the floor of my living room and depositing it on the floor of the basement. I.e. my fan pushes air into the basement.

See here a description:

Post in thread 'Moving heat from basement'

May 1, 2023

I heat from the basement, and if I include my basement squre footage, I have 2500 sqft.
825 in the basement and 1700 above that. Late 70s. Brand new triple pane windows, fantastic sealing and insulation (R57) in the attic. Mediocre wall insulation.

My basement walls are insulated, but the floor is unfortunately not.

Heating my home above the basement is easy. Only when it gets to be 5 F do I have to push the stove (as in 8 hr reloads), still keeping my main floor around 70 F.

However, I second the comment above that heating from a basement benefits from consistency, i.e. you heat...

• stoveliker

• 

Note the discussion about penetration and fire damper.

 

[ccanfield]

Thank you for your input Stoveliker. I don't mind loading a little more often, and would be fine upsizing to a larger stove. With the current setup I have to reload every three hours or so, and the stove is stone cold by morning, temp usually down to about 63 in the house, from 71 or 72ish when we go to bed. It would be nice to have at least a bed of coals to get restarted quicker in the morning.

 

[stoveliker]

I think an 8 hour schedule should be possible - though of course that's at a lower heat output than a 6 hour schedule etc.
In the end, the question is how many BTUs do you need per hour to be where you want to be.

Your current firebox is how many cubic ft? You're using that volume of wood in 3 hrs. But at an efficiency that is likely far lower than the Osburn would be (coal stoves or hybrid coal/wood stoves are notoriously inefficient for wood burning).
If I take the firebox volume from here:

Mark II | Legacy Stoves

legacystoves.com

I get less than 1.3 cubic foot. If that is correct, and your burn rate would be the same with the Osburn, you'd get 3 hrs times 2.4/1.3 is 5.5 hrs out of the Osburn.
BUt your efficiency is likely higher with the Osburn. If I am generous and say that's 25% better, you'd end up with 6.9 hrs *at that heat output*. (Longer at a lower heat output. But then upstairs may get colder again...)
25% may be a stretch though. Not sure.

So, I would say that the Osburn is not (at all) too large.
You could easily go to a 3 cu ft stove imo.

There's of course assumptions in this, and that's that the stoves allows for a same controllability (and thus range of heat outputs accessible) . You can possibly get longer burns (I think so) with the Osburn, but that would then be at a lower heat output.

ANyway, I think the Osburn is sooner too small than too large.
Moreover, you can always make a small fire in a larger stove, but you can't (safely) push a small stove to give larger outputs.

 

[ccanfield]

Those dimensions match up. To be honest I never ran the numbers to calculate output, but it would be worth doing, especially during this cold snap. Calling for a low of 3 here tonight! I would be happy with a larger firebox, maybe I'll look at the 3,000 line, and hope to catch one on sale this spring. Brother in law installed a 3500 in his house three years ago and loves it. I would prefer it warmer in the house honestly, but my lovely bride gets cooked out at 75 degrees and needs to open a window at bedtime.

 

[stoveliker]

I do close the door to our bedroom at night.

 

[begreen]

At 2.4 cu ft, the Osburn 2000 should do the job reasonably well. It's the fancier version of the Drolet Escape 1800 that several folks here have. Burn time will vary with the load size, draft, wood species, etc. but it should be in the 4-8 hr range depending on how hard the stove is pushed. Based on the layout the heating bias will be in the living room area. I'm not sure how the old setup is ducted but it might be adapted, off the stove at ceiling level , to help distribute the heat.

 

[ccanfield]

I was considering reusing the ducting and squirrel cage blower in an adjacent wall to the stove (to be built) to aid in circulation. I looked at the Drolets online, read some threads on here and was a little concerned about not being able to replace the air tubes. From what I read Drolet has them welded in? I understand they are both made by SBI and maybe I was looking at dated information.

 

[ccanfield]

Ducts run to the bedrooms and bathroom upstairs, and to the toe kick in the kitchen

 

[stoveliker]

I would be careful having a fan suck out air from near the stove.

If something goes wrong, you're spreading CO all over the place. If you go this route nonetheless, add a CO detector at the register where you suck in the warm air. (I have CO monitor at the place the warm air passes by when going up the stairs.)

I prefer to push air to the stove, as that helps avoid draft reversal etc. (not sure if you have a door to the basement that closes; then having a fan sucking away air could lead to underpressure in the basement - that is already potentially sensitive to low pressures).

It can all work and be safe, but these are some boundary conditions that are worth thinking about before making the choice to proceed.

 

[ccanfield]

Thanks, I also was concerned with the idea of moving CO. The current setup has a plenum surrounding the entire stove with a low volume squirrel cage fan blowing hot air through the ducts. It’s on a switch and I don’t turn it on until the stove is up to temp to avoid draft issues; learned that lesson the hard way! I haven’t measured the cfm on the output, but it’s low. It will flutter paper on the vent but will not blow it completely off. We have CO detectors near the existing stove, at the base of the stairs and 3 upstairs as well. I would rather err on the side of caution though and will likely try moving the cold air down as you mentioned previously rather than hot air up. I think if I upsize, there honestly would be sufficient radiant heat. I appreciate all the thoughts and suggestions!

 

[begreen]

I was considering reusing the ducting and squirrel cage blower in an adjacent wall to the stove (to be built) to aid in circulation. I looked at the Drolets online, read some threads on here and was a little concerned about not being able to replace the air tubes. From what I read Drolet has them welded in? I understand they are both made by SBI and maybe I was looking at dated information.

That was the baffle, years ago. They haven't had that design for over a decade.
FYI Drolet will be releasing their big Austral III with a similar plenum wrap in January

Wood Stove | Austral III With Heatflow S5 Forced Air System

Austral III wood stove with forced air system Heatflow S5 - Certified at 0.95 g/h - 90 000 BTU/h - Heats up to 2,100 ft² - 20 '' logs - Made in Canada Can.

www.drolet.ca

 

[ccanfield]

Thank you begreen for the information. This is great to know! I don’t need the Cadillac if it does the same job and can be maintained as effectively.