Oven temperature vs Chimney Height

[mikku]

Re: Oven temperature vs Chimney Height

F350..E is the vans

No biggie they are all junk.

Been gone too long from American soil! Don't remember anymore- even though I always bought Fords until my last adventure with a Chevy that I ended up returning under a lemon law provision! That was a real piece of doggie poop from day1!

[stonecutter]

Re: Oven temperature vs Chimney Height

I'm going to be damned to hell for that one! Visualize Gomer Pyle saying that!
E-350 dually--but with performance improvements--right?

A really big "I'm sorry"!

F350..E is the vans

No biggie they are all junk.

[mikku]

Re: Oven temperature vs Chimney Height

No, I really do get what you are saying...and in a convoluted way I am agreeing with you. I just believe a well insulated door can do it all.

But, in less words.... a nice insulated door, in tandem with a damper to stop excess air flow, would make a great set up to maximize heat retention.

How's about a good compromise? Make the "overnight door" wide enough that it covers all exposed area where my present stainless door sits, plus thick enough to cover where the smoke would exit the landing area into the chimney! total would be about 8" thickness... but it would be used totally for retaining heat! Pretty doesn't even count cuz it is for the non-use time to conserve for the in-use time! Both birds with one stone!

Or if I follow your line of reasoning- a well insulated door that covers all exposed area of the oven--disregarding the stack would solve this situation--one is about 6" thinner.

Back from getting my ears lowered--roads are getting snow covered and slippery here, second decent snowfall this year--last week's snow has not melted on the roads entirely so driving is a little dicey in spots.

[mikku]

Re: Oven temperature vs Chimney Height

I've got a Blue Oval, not a Bow-tie.

I'm going to be damned to hell for that one! Visualize Gomer Pyle saying that!
E-350 dually--but with performance improvements--right?

A really big "I'm sorry"!

[stonecutter]

Re: Oven temperature vs Chimney Height

Stonecutter, you are missing my point.
If the cab is warm in a static position, but cold in a moving position it has all to do with the movement of air.

Both conditions have heat loss occurring, however the movement makes the loss more dramatic.

I agree about improving the door--Point taken, my door however is insulated with ceramic fiber BUT there are still points where conduction can occur. However, when my oven is hot and the door is in place, I can put my hand onto the stainless steel handle and open and close the door without burning myself... it is warm but not burning hot! So loss is occurring, also the perimeter of the door has woodstove gasket material that forms a seal. There is no lock like a stove might have, but it can be forced tight with a wedge under the tapered handle.

Right now, I am in the process of constructing an enclosure that will add from 6 to 15" of loose fill perlite/vermiculite around the oven. Now with the oven supported by beams, I can insulate beneath the oven with up to 8" of additional insulation (anything is OK), finally where the structural slab is exposed, I am adding Styrofoam insulation. Choice of conventional insulation materials are in areas that will never be damaged by oven temperatures.
When all is complete, the entire thing will be like a large thermos bottle--only area not super-insulated will be the door.

No, I really do get what you are saying...and in a convoluted way I am agreeing with you. I just believe a well insulated door can do it all.

But, in less words.... a nice insulated door, in tandem with a damper to stop excess air flow, would make a great set up to maximize heat retention.

[stonecutter]

Re: Oven temperature vs Chimney Height

I'm sure that Stonecutters big Chevy doesn't have any leaks in its' cab! It is too well maintained for that! But the big engine with performance improvements might be the reason for it being cooler when he zooms along the highway--but for the next few days, the ice is going to slow forward motion down a lot. Really hope this crazy weather worldwide changes for the better OR we somehow can reverse all the bad things we have done for the earth to heal itself.

I've got a Blue Oval, not a Bow-tie.

[mikku]

Re: Oven temperature vs Chimney Height

Yes, I agree. I think that's a correct analogy to what's going on, so stopping the airflow is the answer. Being winter and the entering air being very cold may also explain part of the greater heat loss.

You should also fix the air leaks in the cab of your truck.

I'm sure that Stonecutters big Chevy doesn't have any leaks in its' cab! It is too well maintained for that! But the big engine with performance improvements might be the reason for it being cooler when he zooms along the highway--but for the next few days, the ice is going to slow forward motion down a lot. Really hope this crazy weather worldwide changes for the better OR we somehow can reverse all the bad things we have done for the earth to heal itself.

[mikku]

Re: Oven temperature vs Chimney Height

Consider this....

The heat is going to be lost somewhere, unless it is contained. In your illustration, the most likely place will be through uninsulated surfaces, like the windows and windshield. When you are driving, air flow is increased over the most conductive surface, which would be your windshield ( like your door panel ) so, your heat loss is greater because it is being removed from the conductive surface faster. The problem isn't the forward motion, it's the uninsulated surface bleeding the heat out. I don't endorse covering your windshield to stay warmer.

The greater vacuum created by your flue isn't the problem, it's your door. I do think a damper may marginally improve the heat loss, simply by restricting the air flowing over the door, but at least to me, why bother when a good door will do the job. Heat that isn't flowing up the flue will be absorbed into the vent masonry, and or lost through the outer opening. You may see improvement with a damper, but not as much as with a very good door.

Stonecutter, you are missing my point.
If the cab is warm in a static position, but cold in a moving position it has all to do with the movement of air.

Both conditions have heat loss occurring, however the movement makes the loss more dramatic.

I agree about improving the door--Point taken, my door however is insulated with ceramic fiber BUT there are still points where conduction can occur. However, when my oven is hot and the door is in place, I can put my hand onto the stainless steel handle and open and close the door without burning myself... it is warm but not burning hot! So loss is occurring, also the perimeter of the door has woodstove gasket material that forms a seal. There is no lock like a stove might have, but it can be forced tight with a wedge under the tapered handle.

Right now, I am in the process of constructing an enclosure that will add from 6 to 15" of loose fill perlite/vermiculite around the oven. Now with the oven supported by beams, I can insulate beneath the oven with up to 8" of additional insulation (anything is OK), finally where the structural slab is exposed, I am adding Styrofoam insulation. Choice of conventional insulation materials are in areas that will never be damaged by oven temperatures.
When all is complete, the entire thing will be like a large thermos bottle--only area not super-insulated will be the door.

[david s]

Re: Oven temperature vs Chimney Height

If your inner door is uninsulated then the cold draft coming in the entry hitting the very conductive stainless inner door will accelerate the heat loss from it and hence the oven.

[stonecutter]

Re: Oven temperature vs Chimney Height

Another way to look at this is: For example:

You are sitting in your truck with the heater on low on a very cold day but the truck feels quite warm and comfortable.

Now you put your truck in gear and go onto an express highway at 70 mph with the heater set the same...

Immediately you feel chilly because the speed you are driving is cooling your cab more rapidly.

Also, the wind passing over your cab makes all the little air leaks more significant.

??That is the way I think of my chimney stack in this situation?? No?

Consider this....

The heat is going to be lost somewhere, unless it is contained. In your illustration, the most likely place will be through uninsulated surfaces, like the windows and windshield. When you are driving, air flow is increased over the most conductive surface, which would be your windshield ( like your door panel ) so, your heat loss is greater because it is being removed from the conductive surface faster. The problem isn't the forward motion, it's the uninsulated surface bleeding the heat out. I don't endorse covering your windshield to stay warmer.

The greater vacuum created by your flue isn't the problem, it's your door. I do think a damper may marginally improve the heat loss, simply by restricting the air flowing over the door, but at least to me, why bother when a good door will do the job. Heat that isn't flowing up the flue will be absorbed into the vent masonry, and or lost through the outer opening. You may see improvement with a damper, but not as much as with a very good door.

[david s]

Re: Oven temperature vs Chimney Height

Another way to look at this is: For example:

You are sitting in your truck with the heater on low on a very cold day but the truck feels quite warm and comfortable.

Now you put your truck in gear and go onto an express highway at 70 mph with the heater set the same...

Immediately you feel chilly because the speed you are driving is cooling your cab more rapidly.

Also, the wind passing over your cab makes all the little air leaks more significant.

??That is the way I think of my chimney stack in this situation?? No?

Yes, I agree. I think that's a correct analogy to what's going on, so stopping the airflow is the answer. Being winter and the entering air being very cold may also explain part of the greater heat loss.

You should also fix the air leaks in the cab of your truck.

[mikku]

Re: Oven temperature vs Chimney Height

Another way to look at this is: For example:

You are sitting in your truck with the heater on low on a very cold day but the truck feels quite warm and comfortable.

Now you put your truck in gear and go onto an express highway at 70 mph with the heater set the same...

Immediately you feel chilly because the speed you are driving is cooling your cab more rapidly.

Also, the wind passing over your cab makes all the little air leaks more significant.

??That is the way I think of my chimney stack in this situation?? No?

[mikku]

Re: Oven temperature vs Chimney Height

Stonecutter, Thank you for your input--as always.

I started this little thread because I noticed a significant difference in "morning after" temperature after extending the chimney. There are several things that I am doing now to better insulate the entire oven now that it is perched on its' final resting place. Those things should improve the heat retention of the oven. But the door has remained the same during this period.

I want to solve the initial problem before getting into redesign of the oven door. My oven door design can be greatly improved with the addition of an insulation layer--like a wood panel that would prevent the conductive heat loss through the stainless skin.

Another option would be an entirely different door to be used when the oven is left unattended. But that is "another rat to be skinned" at another time.

[stonecutter]

Re: Oven temperature vs Chimney Height

A damper wouldn't hurt, but dont you think the real culprit of heat loss is the door design? If heat is leaching through or passing through the door, and then prevented from traveling up the flue by some sort of damper, it is still going to be lost to the oven by being absorbed by the outer masonry or blown out the vent opening.

A damper may slow that heat loss down by reducing air flow across your door, but if the stored heat gets out of the chamber, it is still not really beneficial to the oven....and all a damper will do is prevent the heat from going up into the flue.

[mikku]

Re: Oven temperature vs Chimney Height

This is true, but it all depends upon the seal you can achieve with the outer door. My chimney creates a very strong draft now that it extended above the roofline of the WFO and wood storage structure AND it is not yet and the proper height according to good practices--this would mean another 6 feet of stack!