Wood stove design theory and sizing?

[mckray]

Hi,

I have a legacy FireView Wood Heater that has some design issues I'm trying to fix. Regardless of how hot I get the chimney and vent the room, smoke pours out.

I helped smoke from coming out of the side door by partially sealing the side door. See photo (bottom left screw problem was fixed after taking the photo). The plate's attached by four screws so it can be removed for cleaning and fresh screws installed. It's reinforced from warping with 1:" channel steel on the back. Holes are oversized to allow expansion. I've been running it for three weeks with no smoke or other issues.

Now, I'm trying to solve the smoke problem from the front side.

The design at the front door left large gaps around the foldable shield that allowed lots of air through. As a result, smoke comes out from the front when loading from the side. I helped the problem partially by adding some gasketing around the foldable shield behind the window, but I wanted better performance so I removed the shield and wanted to see what would happen if I sealed everything but the top vent to allow for a clean air stream across the window.

Now, the sides are sealed with blocking plates, but even when the top door is closed, smoke leaves when the side door is open more than a few inches. I have a few more places I could seal: around the window edges and the top door, both somewhat difficult to seal, but I wanted to see if I could make the front a door as well. I've tried to run the stove without the window in place, and smoke pours out readily when the stove is warm. I haven't attempted to remove a hot window or run it without the window until the stove gets hot. Because smoke poured out with the glass off, I assume I would not be able to keep a front door the same size as the window.

One mod I already had planned for summer is to convert it from a rear exit to a top exit. I was thinking it would be a good idea to upsize to an 8-inch stovepipe to allow for more flow.

My questions are:

• How can I calculate the added gas volume from pyrolization?
• How do I calculate areas for entry and exit on a wood stove?

I have experience in aerospace engineering mechanics, but I don't have experience with combustion calculation, especially not with solid fuels.

Thank you!

 

[bholler]

Hi,

I have a legacy FireView Wood Heater that has some design issues I'm trying to fix. Regardless of how hot I get the chimney and vent the room, smoke pours out.

View attachment 291290View attachment 291291

I helped smoke from coming out of the side door by partially sealing the side door. See photo (bottom left screw problem was fixed after taking the photo). The plate's attached by four screws so it can be removed for cleaning and fresh screws installed. It's reinforced from warping with 1:" channel steel on the back. Holes are oversized to allow expansion. I've been running it for three weeks with no smoke or other issues.

View attachment 291288View attachment 291289

Now, I'm trying to solve the smoke problem from the front side.

The design at the front door left large gaps around the foldable shield that allowed lots of air through. As a result, smoke comes out from the front when loading from the side. I helped the problem partially by adding some gasketing around the foldable shield behind the window, but I wanted better performance so I removed the shield and wanted to see what would happen if I sealed everything but the top vent to allow for a clean air stream across the window.

Now, the sides are sealed with blocking plates, but even when the top door is closed, smoke leaves when the side door is open more than a few inches. I have a few more places I could seal: around the window edges and the top door, both somewhat difficult to seal, but I wanted to see if I could make the front a door as well. I've tried to run the stove without the window in place, and smoke pours out readily when the stove is warm. I haven't attempted to remove a hot window or run it without the window until the stove gets hot. Because smoke poured out with the glass off, I assume I would not be able to keep a front door the same size as the window.

One mod I already had planned for summer is to convert it from a rear exit to a top exit. I was thinking it would be a good idea to upsize to an 8-inch stovepipe to allow for more flow.

My questions are:

• How can I calculate the added gas volume from pyrolization?
• How do I calculate areas for entry and exit on a wood stove?

I have experience in aerospace engineering mechanics, but I don't have experience with combustion calculation, especially not with solid fuels.

Thank you!

Isn't there glass sealing the front?

These are pretty primetive heaters but they did generally work fairly well. What size type and height chimney do you have? Chances are it is a chimney issue more than a stove issue.

 

[mckray]

Isn't there glass sealing the front?

These are pretty primetive heaters but they did generally work fairly well. What size type and height chimney do you have? Chances are it is a chimney issue more than a stove issue.

I haven't measured my chimney, but it's exterior, 7" square clay liner with 3 ft or so height above a two-story house. I'd estimate 28 ft or so. The stovepipe runs about 20" horizontally and I have 3 90deg bends to get to the chimney, I'm assuming the 90s are a big part of it which is why I want to convert the stove to a top exit. It does have some leakage to an adjacent liner that was left over from a boiler at the bottom clean out. Would that affect the draft enough to cause this?

The glass seal was this fiberglass seal tape that I can't seem to find. The tape isn't there anymore, but the leakage is minimal. Other than that, the 1/8th sheet steel door on top has warped over time, and even if it wasn't warped, the hinges hold it off the stove by about 1/16"

 

[bholler]

I haven't measured my chimney, but it's exterior, 7" square clay liner with 3 ft or so height above a two-story house. I'd estimate 28 ft or so. The stovepipe runs about 20" horizontally and I have 3 90deg bends to get to the chimney, I'm assuming the 90s are a big part of it which is why I want to convert the stove to a top exit. It does have some leakage to an adjacent liner that was left over from a boiler at the bottom clean out. Would that affect the draft enough to cause this?

The glass seal was this fiberglass seal tape that I can't seem to find. The tape isn't there anymore, but the leakage is minimal. Other than that, the 1/8th sheet steel door on top has warped over time, and even if it wasn't warped, the hinges hold it off the stove by about 1/16"

Yes leaking out of the flue will cause problems both with performance and safety. As far as the stove goes it really sounds like this one is past it's useful life

 

[mckray]

Yes leaking out of the flue will cause problems both with performance and safety. As far as the stove goes it really sounds like this one is past it's useful life

You're probably right - but it has so much character and steel is so easy to fix! (if only I could find it in the budget to get a welder)

I guess I didn't really think twice when I noticed there was a huge opportunity for air to exchange between the two flues. Is there an easy way to seal or isolate the bottom of the stove's? What's the right way to do that?

 

[bholler]

You're probably right - but it has so much character and steel is so easy to fix! (if only I could find it in the budget to get a welder)

I guess I didn't really think twice when I noticed there was a huge opportunity for air to exchange between the two flues. Is there an easy way to seal or isolate the bottom of the stove's? What's the right way to do that?

The right way is to install a new liner.

 

[mckray]

The right way is to install a new liner.

Guess I'd better get a local pro on it - thanks for the help!

 

[RockyMtnGriz]

There were a lot of those in the mountains of CA when I was growing up - too long ago. It was a common modification to weld the front of those stoves shut. In addition to the smoke leakage you're experiencing, the fire viewing bit usually didn't work that well, and with the original leaky front, there wasn't much slowing things down in the event of a hot chimney fire. In fact, there wasn't much slowing those stoves down period, until they ran out of wood. Welded up, they became more controllable smoke dragons.

It was also common for the end opposite the door to have damage from overheating, as they could really crank out the heat, and the end is not bricked.

I'd definitely have one as an occasional use, shop / garage stove.

 

[stoveliker]

You can also help the draft (sucking in air, so countering smoke coming out) by replacing 90s with two 45s and minimize the horizontal run (or slanting it upward more).

 

[begreen]

The draft is weak. Resolve that issue and the smoke rollout should stop.
From the thread the 2 takeaways are:

Cold, exterior chimney without an insulated 6" liner​

Lower floor (basement) install in a possible negative pressure zone.​

 

[mckray]

There were a lot of those in the mountains of CA when I was growing up - too long ago. It was a common modification to weld the front of those stoves shut. In addition to the smoke leakage you're experiencing, the fire viewing bit usually didn't work that well, and with the original leaky front, there wasn't much slowing things down in the event of a hot chimney fire. In fact, there wasn't much slowing those stoves down period, until they ran out of wood. Welded up, they became more controllable smoke dragons.

It was also common for the end opposite the door to have damage from overheating, as they could really crank out the heat, and the end is not bricked.

I'd definitely have one as an occasional use, shop / garage stove.

I've had that experience as well. Until I partially sealed the front, she would just go.

And I can see the far end getting damaged. There's a tight jet of air pointed right at it from under the side door. I'm not sure if it's stock, but there's an internal heat shield attached that is pretty warped. I'm guessing it's been doing its job.

You can also help the draft (sucking in air, so countering smoke coming out) by replacing 90s with two 45s and minimize the horizontal run (or slanting it upward more).

I've been thinking about this, but after the discussion in this thread, I think the savings would be marginal compared to a proper liner installation.

The draft is weak. Resolve that issue and the smoke rollout should stop.
From the thread the 2 takeaways are:

Cold, exterior chimney without an insulated 6" liner​

Lower floor (basement) install in a possible negative pressure zone.​

I've opened the basement windows and it doesn't resolve the issue, but installing an insulated liner is definitely on my list.

It has 7" out the back of the stove. Should I continue that or go 6"? It's about a 26% reduction in area by my math but I've also read that a slightly smaller diameter can help keep the temp (and thus velocity) of the flow up.

 

[RockyMtnGriz]

From what I can remember from my youth, that stove will probably do better with a 7 or even an 8 inch flue. They put a lot of heat up the chimney, so I don't think you're going to have a concern with the chimney not drawing well enough, and the larger flue should draw more air in when you open the door or front, to counter the smoking.

Not to rain on the parade, but the problem I see in going to the larger flue, is it's probably not going to work as well as a smaller one if you get tired of this stove. There are a lot of these sitting outside and in sheds for a reason. People got tired of a stove that had no chance of burning overnight, that they didn't feel comfortable with leaving burning unattended, and ate a lot of wood. They replaced them with a modern stove, most of which want a 6" flue. You might give some thought to what stove you would want to replace this with someday and let that help guide your decision. I think one of the few modern stoves wanting an 8" flue is a Blaze King King, and I could be wrong about that. If I thought that might be my stove someday, I'd sure go with an 8" now.

 

[begreen]

This is a spinoff of the Orley design. The Orley had a smoke shield, not unlike the one that you put in but out of stouter stock. Does Oregon still have the old stove replacement program in effect? If so, I would lose the old Fireview to it when the new liner goes in and install a 6" insulated liner for a modern stove.

 

[mckray]

From what I can remember from my youth, that stove will probably do better with a 7 or even an 8 inch flue. They put a lot of heat up the chimney, so I don't think you're going to have a concern with the chimney not drawing well enough, and the larger flue should draw more air in when you open the door or front, to counter the smoking.

Not to rain on the parade, but the problem I see in going to the larger flue, is it's probably not going to work as well as a smaller one if you get tired of this stove. There are a lot of these sitting outside and in sheds for a reason. People got tired of a stove that had no chance of burning overnight, that they didn't feel comfortable with leaving burning unattended, and ate a lot of wood. They replaced them with a modern stove, most of which want a 6" flue. You might give some thought to what stove you would want to replace this with someday and let that help guide your decision. I think one of the few modern stoves wanting an 8" flue is a Blaze King King, and I could be wrong about that. If I thought that might be my stove someday, I'd sure go with an 8" now.

Good to know - I'm definitely planning on moving this to a shop and replacing with something nicer. I've had my eye on a Pacific Energy Summit. I like the Blaze Kings (esp. the efficiency) but I have some reservations about going catalytic. I don't know what the common opinion is on those here, but it just seems like it's another thing to go wrong. Plus, the secondary burn tech is just.. more interesting I guess. I'm taking some design cues from Pacific Energy to tinker with and mod this Fire View eventually.

This is a spinoff of the Orley design. The Orley had a smoke shield, not unlike the one that you put in but out of stouter stock. Does Oregon still have the old stove replacement program in effect? If so, I would lose the old Fireview to it when the new liner goes in and install a 6" insulated liner for a modern stove.

Wow, that's the proper build! It looks like they had something figured out. The Fire View is built with thinner material all around.

I'm in Mass but I'll check to see about programs like that, they've got a lot of good eco programs so there's bound to be something.

 

[RockyMtnGriz]

Begreen - that's an interesting photo. I don't think I've ever seen an Orley, or if I did, I didn't see the door and thought it was a Fire View. I can see why they needed a smoke flap on that stove. The door area is about twice that of the Fire View, and they smoke badly enough. They don't only smoke from the door, but from the unsealed front viewing area when the door is open (and sometimes at other times, too).

Superb point about the stove subsidies, especially for flue work. Kinda sad that the Fire View in good condition becomes the "throw down" stove at that point, though. They didn't smoke that much because you couldn't slow them down. Maybe he should get something truly crappy to put in its place first, if he has to hand over the old one.

I think the OP is in Boston, so that is another reason that I think he's going to want to go to a modern stove at some point. I had a Fire View in a house for a bit, and while it was fun at the time, the fact that it was in a climate where the lows were seldom below 20, and the days were seldom below freezing, I'm sure made it a lot more fun. It would be tough to tolerate one in a cold climate. It was -26 here this morning, and a good thing to have the stove still putting out heat when I got up!