How can I get this stove to draft better?

[human69]

I have experimented with veg oil and alcohol for this stove that's in my van. It's got an issue where it backdrafts as soon as you open the door. It doesn't draft well. Some have said because the pipe is not straight, but I didn't want to go through the roof.

Things I've thought of:

1. Putting a 3 inch air intake through the floor of the van up into the stove. Which is a little tricky as I'd like to be able to use it as a vent in the summer too. So trying to figure how to pipe it all up and make it tight and closeable so it doesn't get a bunch of dirt from the rode would be good. I tried putting one on the back of the stove that goes into the drafty drivers area but it didn't work well being opposite the door. If you got any ideas and what to use please share.
2. Change the 90 degree pipe to a 45 degree pipe. But it won't fit through the wall nicely as is so it might need a 2nd small 45 right before it goes through the wall because there is a flange in there that fits the existing 90 degree.
3. I've heard put an extension on the outlet outside that goes straight up. I made a makeshift one to test that went above the roof and it didn't work well and it's not convenient to be putting it on and off daily.

The 90 degree pipe has a 3 inch exhaust flange right before it goes out the wall so with that you can't put a 45 through it.



That's a pic of the air intake but it didn't help i think cause it's opposite the door but even if i block it it tends to backdraft when i open the door.

I think going straight up through the floor would be better but not sure.

 

[bholler]

You need more height on your chimney

 

[stoveliker]

Stoves don't draft, chimneys do.
The warm air going up creates a low pressure in the stove that then results in air being sucked into the inlet.

So your stove is fine but your chimney doesn't provide what the stove needs.

Solution, see above.

(Also, do you have a CO detector? And are clearances to combustibles met? Doesn't matter if there is a non-combustible sheet before something combustible; the distance to the hidden combustible is what matters. And Is the floor non-combustible far enough in front of the stove?

If you only use this with alcohol burners I'd not be so concerned about this, tho.)

 

[human69]

Stoves don't draft, chimneys do.
The warm air going up creates a low pressure in the stove that then results in air being sucked into the inlet.

So your stove is fine but your chimney doesn't provide what the stove needs.

Solution, see above.

(Also, do you have a CO detector? And are clearances to combustibles met? Doesn't matter if there is a non-combustible sheet before something combustible; the distance to the hidden combustible is what matters. And Is the floor non-combustible far enough in front of the stove?

If you only use this with alcohol burners I'd not be so concerned about this, tho.)

It's not a home it's a van and it's not a wood burner, more like a candle burner atm. So then everyone here is aying it's the bend and it's not long enough which may be right although... I have done some searches for horizontal chimneys and have seen some short ones that terminate horizontally.

 

[4x4prepper]

Try attaching a six inch anything to the pipe sticking out the wall and see if you get the back draft. imo, When you let the hot air out, open the door, the cold air rushes in through the chimney pipe because it is inside of the envelope around the structure. If you have a very hot fire, it probably will not back draft as much.

The older gypsy wagons and home made mobile homes from years past I remember seeing usually had a 12" or longer vertical exit for their wood stoves.

 

[human69]

" the cold air rushes in through the chimney pipe because it is inside of the envelope around the structure.

the cold air rushes in through the chimney pipe because it is inside of the envelope around the structure.

thanks. I am trying to understand what you mean. So you are saying when i open the door to the stove the outside air is coming down the pipe? but the last part i dont quite get.

you dont think a floor intake or 45 degree pipe would matter?

 

[bholler]

It's not a home it's a van and it's not a wood burner, more like a candle burner atm. So then everyone here is aying it's the bend and it's not long enough which may be right although... I have done some searches for horizontal chimneys and have seen some short ones that terminate horizontally.

It doesn't matter if it's a home or not. It doesn't matter what the fuel is. You need enough height and enough heat in that pipe to create adequate vacuum to suck the fumes out. You need more height period. Now is the stove designed properly and the vent sized for that stove properly that's an entirely different question that would require much more information to figure out

 

[stoveliker]

There are horizontal ending chimneys but they have a fan pushing the gases out so that natural draft as determined by the physics of warm air (think hot air balloons ) is not needed. Pellet stoves and natural gas furnace can have that.

 

[begreen]

It's weak or no draft. Adding a few feet of vertical flue pipe to the exterior may help, but smoke and fumes negotiating the two 90º turns with weak draft may not cut it, especially when it's above 45º outside. Going straight-up, vertically through the roof, would perform significantly better.

 

[4x4prepper]

When you install a vent for a P-trap (sewer) or vented range hood there are building codes that require you to make the pipe so many inches high (depending on pipe size) compared to the next available surface within ## of feet. I have seen this on various wood stoves and inside Duravent manuals too,

google "turbulence surrounding structures examples"

https://www.sciencebuddies.org/science-fair-projects/project-ideas/EnvEng_p029/environmental-engineering/detecting-turbulence-around-structures

The side of a structure is not the ideal place to empty a chimney without a blower.

If you install the fresh air vent so it is outside the truck body that would help, I would think the side might be better then the floor. I think the air flow over a truck or van body would create a slight vacuum depending on wind speed, but, that is an engineering question which I can not answer since I am not an engineer nor have I played one on TV :-D

My wood stove pipe makes a 90 degree up turn exiting my wall and only sits maybe 36" above the roof, but, the vertical chimney pipe itself is 8+ feet long. So, it vents well, BUT, because it is not high enough, it actually back drafts the smoke through my range hood vent pipe sometimes because it is not high enough and/or the chimney is not high enough.

If it was me, I would go straight up through the roof and have it at least six inches above the roof, with a cover.

> So you are saying when i open the door to the stove the outside air is coming down the pipe?

That is what a back draft is, which can be deadly on a gas appliance. People used to die of that every year when I lived up north. Not enough fresh air and not a long enough vent pipe. It is why gas powered generators are now coming with detectors and/or sensors. People place generators too close to the house.

 

[stoveliker]

For wood stoves (which this is, even if one burns candles) that is the 3-2-10 rule. In feet, not inches.

 

[begreen]

For wood stoves (which this is, even if one burns candles) that is the 3-2-10 rule. In feet, not inches.

That's residential code. It doesn't apply to boats or caravans.

 

[stoveliker]

Yes, I'm not sure there is any code for boats or caravans.
Yet the safety reasons underlying residential code are good too to take into account here.

 

[gthomas785]

In addition to the height as others have mentioned, temperature also affects draft. How hot are the fires you're building and is there any way you could insulate that pipe to raise the temperature?

 

[Max W]

I would go back to your original idea of 2 45 deg’s along with going vertical on the outside then try kick starting draft with some lighted paper. After that it may be the roof or nothing. In a boat I had a wall mounted stove that drew well despite a three inch pipe and extremely short rise but it went straight up. Using small chunks of hardwood maybe 21/2 , 3 inches heated well and was manageable as long as I didn’t overload.

 

[begreen]

I would go back to your original idea of 2 45 deg’s along with going vertical on the outside then try kick starting draft with some lighted paper. After that it may be the roof or nothing. In a boat I had a wall mounted stove that drew well despite a three inch pipe and extremely short rise but it went straight up. Using small chunks of hardwood maybe 21/2 , 3 inches heated well and was manageable as long as I didn’t overload.

Straight up through the roof is what's required here.

 

[EatenByLimestone]

In addition to the height as others have mentioned, temperature also affects draft. How hot are the fires you're building and is there any way you could insulate that pipe to raise the temperature?

Yes. The “candle” might not be enough heat to warm the flue.

 

[human69]

The side of a structure is not the ideal place to empty a chimney without a blower.

If you install the fresh air vent so it is outside the truck body that would help, I would think the side might be better then the floor. I think the air flow over a truck or van body would create a slight vacuum depending on wind speed, but, that is an engineering question which I can not answer since I am not an engineer nor have I played one on TV :-D

If it was me, I would go straight up through the roof and have it at least six inches above the roof, with a cover.

Interesting you said blower. Because i have been researching waste oil burners and most of them use some sort of blower or fan if that's the kind of fan you mean. But i think they use the fan to fuel the fire not exhaust. Where would you put the fan?

So I can't go through the wall next to the stove for an intake since it is a pocket door so that's why i thought of the floor. I am hoping that doing that would change it up and create a draft. I am going to get another 90 degree elbow to put on the outside so it's pointing up and see if that helps too.

 

[human69]

It's weak or no draft. Adding a few feet of vertical flue pipe to the exterior may help, but smoke and fumes negotiating the two 90º turns with weak draft may not cut it, especially when it's above 45º outside. Going straight-up, vertically through the roof, would perform significantly better.

Yeah I'll try putting another 90 elbow on the outside. Not convinced it will work either as I did try a makeshift one but true test will be proper fitting pipe.

You think a 45 degree would help? Not sure it can exit the wall at that angle though.

 

[human69]

There are horizontal ending chimneys but they have a fan pushing the gases out so that natural draft as determined by the physics of warm air (think hot air balloons ) is not needed. Pellet stoves and natural gas furnace can have that.

Where would you put the fan on that kind of stove to push the exhaust out?

 

[kborndale]

All those 90s are killing your draft, you need less ,90s, not more.

 

[stoveliker]

Where would you put the fan on that kind of stove to push the exhaust out?

I would not, on a wood stove; the exhaust is far too hot for most fans.
One could add a fan on the air input (pushing the stream of air through the stove rather than pulling it), but that is highly dangerous if the exhaust can't accommodate the total amount of air pushed in as then it'll leak out of the stove elsewhere, with CO and smoke.

Stoves work by having a proper chimney set up. The chimney is the engine that runs the stove.
Warm air/exhaust rises. Just as in a hot air balloon. Having that in a chimney it'll go up and by doing so create a low pressure (partial vacuum, but a very minimal one) in the stove. That makes the stove suck in air through the air inlet. It is that air that allows combustion of the fuel.

"Stoves don't draft" is a wrong understanding of a system. A chimney drafts (sucks air) and a stove needs a certain "suction" on its exhaust to get enough air in so it can properly combust the fuel.

Therefore, all (!) comments here are pointing to you needing a proper chimney.
It's like putting a 25 cc moped engine in a hummer and then complaining the hummer is bad because it won't drive. No, you need the proper engine for the car. You need the proper chimney for the stove.
You can try to add a sail on the car, or a donkey in front of it, but this can be awkward, can be dangerous in traffic, and just won't work well.

Don't mess with fans, just get the proper engine = chimney set up that the stove needs.


A proper chimney has enough height as increased height increases its draft.
Any horizontal sections and elbows decrease draft.

 

[EatenByLimestone]

When the fan quits for whatever reason, all the combustion byproducts go straight into the van. Do it right. You’re in laying with fire here.

With the right chimney, there is a slight negative pressure in the burn chamber. This keeps the byproducts from leaking out.

 

[begreen]

Yeah I'll try putting another 90 elbow on the outside. Not convinced it will work either as I did try a makeshift one but true test will be proper fitting pipe.

You think a 45 degree would help? Not sure it can exit the wall at that angle though.

No, the right way to do this is straight up through the roof. There are good boat fittings for this.