Fire Box Sizes

[wkpoor]

Sometime back I was asking about new stoves and was mentioning how I thought all the new EPA stoves were very small to me. Then many of you chimed in how this and that stove were big enough to cremate a St Bernard and so on. Well I just measured the old Nashua (and by the way mine is a mid size model) and I come up with 5.4 cuft. and I rounded all measurements down. Thats over 1 cuft larger than the King. So my intuition was right. These new stoves are small and they look it. So even though they are real efficient and clean burning just how is a much smaller box going to radiate as much heat as a larger one assuming they burn at similar surface temps?I've got real doubts now that the Magnolia test stove at 150lbs less weight and much smaller fire box can possibly do what the old Nashua is doing. I will say though maybe part of my creosote problem is just the enormous amount of wood I'm burning in the old beast.

 

[begreen]

The Nashua was a respectable heating machine. What are the dimensions of the firebox in your stove?

PS: If you are going to compare the Nashua to a new stove, pick out a rough equivalent instead of a cheap, new stove. The Nashua was build like a tank. But there are solid, stout new stoves. For comparison, our 3 cu ft stove weighs in at 585# and is a modern design.

 

[wkpoor]

FB size is 29wx20hx16d. Only reason I mentioned the Mag was because I have one out in the garage I mean to bring in to try a newer stove. I just decided tonight to actually measure the FB to see what size it is. It basically confirms my thoughts about new stove sizes.

 

[oldspark]

Now that I have the air flow in my house fixed I think the Summit will heat the house easily for the most part and I did not believe that before, they extract more heat from the wood and stay hot forever with just coals from good wood so the fire box can be smaller. For brute force it's hard to beat the Nashua but for the first time since I bought it I am impressed with the Summit.

 

[heatxchanger]

wkpoor,

What size chimney pipe (inside diameter) does your old Nashua require?

 

[wkpoor]

wkpoor,

What size chimney pipe (inside diameter) does your old Nashua require?

Its an 8" outlet from the stove that I have reduced to 6". Only reason it seems to work I'm guessing is the 35' chimney pipe+6' of stove pipe that creates really good draft.

 

[Renovation]

for the first time since I bought it I am impressed with the Summit.

Yay! Rockin' good news, Sparky!

 

[Renovation]

Its an 8" outlet from the stove that I have reduced to 6". Only reason it seems to work I'm guessing is the 35' chimney pipe+6' of stove pipe that creates really good draft.

Don't encourage me.

 

[SolarAndWood]

I come up with 5.4 cuft. and I rounded all measurements down. Thats over 1 cuft larger than the King.

I'd say better than 1.5 cu ft bigger, real world is 3.75 for the King. I would love to see them make a 5.4 cu ft stove. Although, at that point you would need a full large wheel barrow to load it. Now, its just one of the big round feed totes.

 

[wkpoor]

I need to measure my neighbors stove today. His is an 80's smoker too but I'm guessing his firebox to be well over 10cubes and probably closer to 12. It has an 8" flue and man can that thing roar the heat out. He heats a 28x60 shop with it and it gets uncomfortably hot in there to the point of leaving the entrance door open sometimes.

 

[laynes69]

Our old woodfurnace was almost double the size of our new EPA furnace. I will say that the old threw out more heat but for a short period of time. Also the burns were much shorter. With the new unit burning up the smoke that was wasted in the old, it throws out more BTU's over a longer period of time. Therefore we use less wood to stay at a comfortable level. We buttoned up the house quite a but and have more to go, but we used less propane with the new woodfurnace and dropped at least 2 cords from the old. At first I was skeptical, but after I realized the difference of a "EPA" unit the difference was amazing.

 

[oldspark]

Our old woodfurnace was almost double the size of our new EPA furnace. I will say that the old threw out more heat but for a short period of time. Also the burns were much shorter. With the new unit burning up the smoke that was wasted in the old, it throws out more BTU's over a longer period of time. Therefore we use less wood to stay at a comfortable level. We buttoned up the house quite a but and have more to go, but we used less propane with the new woodfurnace and dropped at least 2 cords from the old. At first I was skeptical, but after I realized the difference of a "EPA" unit the difference was amazing.

That pretty much says it all.

 

[BrotherBart]

My old stove was 4.3cf and the replacement 3.5. I used to pack every bit of that 4.3 that I could and now only load to the top of the firebrick in the replacement. So I am only using 3.0cf of the newer stove for the wood charge. And it heats better and longer than the old stove.

But I encourage anybody that thinks that their old stove is doing fine to just keep the danged thing. :smirk: There is a learning curve with the newer stoves and you will just drive yourself nuts for a while thinking the old one was better. And there are hundreds of posts here to prove it.

 

[wkpoor]

You guys are right about the up and downs of the old stoves. In order for me to maintain 500+ stove top I need to add wood every hour. Its easy to get the temp up there but the consumption is so fast it won't stay long. I agree less heat but for longer time would be more beneficial. Only thing that saves me is I'm heating up alot of concrete around the stove and the floor too that gives back for many hours.

 

[oldspark]

.

But I encourage anybody that thinks that their old stove is doing fine to just keep the danged thing. :smirk: There is a learning curve with the newer stoves and you will just drive yourself nuts for a while thinking the old one was better. And there are hundreds of posts here to prove it.

That's a head scratcher, mixed feelings about that, nice to burn cleaner and cut less wood, I agree some what but some of the most important points are easy to understand but I found out the hard way some times the questions are misunderstood, I do know one thing with out this forum the learning curve would be much longer.

 

[jharkin]

Ive gotta ask, how big of a house are you guys heating with 5 cu ft stoves??

 

[dkf5]

Hi wkpoor, We have the Magnolia. We just bought it about 6 weeks ago. We've been burning 24/7. Love the decision on buying this stove, as we had a budget to work with. It heats our house 1st and 2nd floors and we have had some pretty cold weather as of late and will soon be back into it again. We have coals in the morning and when we get home from work. The only complaint that I have is the ash tray is very small. On our old Shennandoah we had a good sized tray. As for everything else we are very pleased.

 

[Battenkiller]

If you are going to compare the Nashua to a new stove, pick out a rough equivalent instead of a cheap, new stove. For comparison, our 3 cu ft stove weighs in at 585# and is a modern design.

Weight is nice once you get it up to temp, but weight ain't pumping out the heat, just storing it. If you compare radiant designs, the stove with the greatest surface area will put out the greatest amount of heat at the same overall average surface temperature. This will be true no matter what the material.

 

[wkpoor]

Weight is nice once you get it up to temp, but weight ain’t pumping out the heat, just storing it. If you compare radiant designs, the stove with the greatest surface area will put out the greatest amount of heat at the same overall average temperature. This will be true no matter what the material.

Well that kinda one point I've been thinking about. The sheer size of the old stove makes for alot of radiant area. But I see the point about smaller more efficient stoves putting out more even heat for a longer time.
I'm heating 2800sqft on 3 floors. Its 18 degrees out now with a pretty stiff wind. Basement is 80 and top2 floors are 70. Plenty of heat downstairs, just need to get some up. Got plans for that soon.

 

[precaud]

Only thing that saves me is I'm heating up alot of concrete around the stove and the floor too that gives back for many hours.

If this concrete is directly coupled to the ground then you would be better off insulating it and NOT trying to store heat in it. Remember, heat transfer always moves toward to greatest temperature difference. The earth is a heat sink with an insatiable appetite. I bet you'd be surprised how much more useable heat you get if you stop dumping it into uninsulated masses.

 

[wkpoor]

Only thing that saves me is I'm heating up alot of concrete around the stove and the floor too that gives back for many hours.

If this concrete is directly coupled to the ground then you would be better off insulating it and NOT trying to store heat in it. Remember, heat transfer always moves toward to greatest temperature difference. The earth is a heat sink with an insatiable appetite. I bet you'd be surprised how much more useable heat you get if you stop dumping it into uninsulated masses.

The block walls of the basement have 2" foam attached on the dirt side. The floor of coarse is just poured over the ground. The walls close to the stove get so hot you can"t hardly touch them and the floor will burn your bare feet close to the stove.

 

[precaud]

Good deal on the walls. Nevertheless, you'd be better not dumping heat into the floor.

 

[oldspark]

The concrete floor is not too bad if there is insulation around the edges and it keeps the ground from freezing.

 

[Battenkiller]

The earth is a heat sink with an insatiable appetite.

Sounds good, but not totally accurate. For one thing, you are neglecting the thermal conductivity of concrete. Well-cured concrete has a fairly low thermal conductivity (around 0.8 W·m−1·K−1), so it actually has fair insulating properties. Also, there will come a point where the temperature of the ground and the material directly above it will be at the same temperature (around 55ºF) and no further heat transfer will occur. I can't say how deep that point will occur under a basement floor, but I will say that the floor in front of my stove has reached temps close to 200ºF as measured by my IR gun. No barefoot loading at that point. lol

If I let the stove go completely out, the floor will still be quite warm but the stove will be cold. It takes several weeks for it to reach it's heat "saturation point" (determined by the mean heat output of the stove), but once it does there is a lot of heat stored in that slab and the earth immediately below it. My basement walls, however, are well insulated, because the frost line around here extends down 3 1/2'. Ground temps that low promote much more rapid heat transfer than that lost through the slab.

Besides, it's easy to insulate basement walls, but quite impractical to insulate a slab after it is poured.

 

[precaud]

Batten, are you suggesting that, with a surface temp of 200F, and some point beneath the surface where the substrate = ground temp, that the heat does not continue to dissipate into the ground? That makes no sense to me.

When I redid my hearth, I insulated (R8) behind the brick to minimize loss into the outside wall. It does indeed retain heat quite well.

It sounds like your stove doesn't have a bottom heat shield.