Exhaust Heat

Re: Exhaust Heat

PostBy: franco b On: Tue Jan 15, 2013 6:43 pm

joeq wrote:Which brings me back to my original question. FB, you state the baros stop excessive draft, however is there a benefit to slowing the draft down in an attempt to retain more heat in the house? Or by installing a baro, my intake damper will be more effective in controlling the stove out-put, and don't even worry about choking down the draft? (like I can with the MPD)

A baro will respond quicker than the thermostat but if the thermostat air damper is sealing well, which yours might not be, then I don't think you will see a difference.

Part of the reason your stove is so efficient is that it uses a comparatively shallow bed of coal but burns it hotter. This does a much better job of burning carbon monoxide than a stove with a deep bed of coal with the air restricted. The deeper bed of coal with a larger grate area however,will burn much longer. There just isn't as much burning coal in your stove so it needs more frequent tending to supply your needs. Your stove should be able to burn about 40 pounds of coal in 24 hours with 8 hour tending intervals. If you are trying to burn more than that you will lose some efficiency and tending intervals will shrink.

One possible solution would be to sell your stove and replace it with the larger 713 Gotha. I don't think it would cost you anything aside from the hassle of moving a very heavy stove.
franco b
 
Hand Fed Coal Stove: V ermont Castings 2310, Franco Belge 262
Baseburners & Antiques: Glenwood Modern Oak 114
Coal Size/Type: nut and pea

Re: Exhaust Heat

PostBy: Lightning On: Tue Jan 15, 2013 7:24 pm

Hmmm.. A baro and MPD kinda have the same objective. They both reduce the ability of the chimney to draw the flue gases out of the stove. That said, they perform this function by using a different technique. A manual pipe damper slows the flue gases by restricting the opening that they must escape thru.. That part is easy... A baro reduces the flow of flue gases by reducing the negative draft pressure in the flue pipe. This is possible by a weighted door that opens after a desired negative flue pressure has been exceeded..

The list of pros and cons with a MPD vrs a Baro is quite extensive and very controversial.. :lol: To name a few, a manual damper can't take spikes from wind quite as well as a baro can since a baro "auto regulates" draft just by its design. Same thing happens when it warms up and cools down outside. Ditto this as the chimney warms and cools. A MPD can't maintain an equal draft pressure at one setting - it needs to be manually changed when temperure changes outside. A baro takes some of the maintenance out of the 12 hour burn by automatically regulating the draft for you.

A baro also steals air in the stove room and sends it up the chimney. This air must be replaced, and that happens thru air infiltration from outside. Meaning, that air is being replaced by air thats coming in every creek and crevasse possible.. Under doors, leaky window sills, cracks in the mortar of the foundation, even a mouse hole :lol:

I feel there is some misconception about closing manual dampers and setting up baros as a way to "hold" heat in the stove because we think of heat thats rising under its own power of convection. Its a given that heat rises but there is a little more going on here. The heated exhaust can't rise UNLESS there is something (in this case more heated exhaust) to replace it. Same concept as mentioned above :idea: Its all about physics... An airtight combustion chamber (good seals and gaskets on the doors) can only send out what comes in.. In other words, think of air in volume.. If a gallon of air goes in under the grates to feed the fire, then only a gallon of air + coal exhaust and some heat is going to go up the chimney. It doesn't matter if that gallon of air is under a .01" WC or a .03" WC..

Lets say a gallon of air passes thru the combustion air opening in 5 seconds at .01" WC... Now, lets increase the negative draft pressure to a .03" WC and at the same time, we will reduce the combustion air setting so that the same amount (one gallon of air) passes thru it in the same amount of time (5 seconds). (IF this isn't reduced, more air will come thru the same size opening) What happened in 5 seconds in both these circumstances? A gallon of air entered the combustion air feed and a gallon of air + coal exhaust and some heat went up the chimney at two different pressures..

I wanted to edit in a clarification -
What all this means is, the determining factor on heat going up the chimney is dictated by the amount of primary and over the fire air that is going into the combustion chamber. The size of the hole its exiting (MPD) or the pressure that its exiting at (Baro) don't have any real bearing on holding heat in the stove OTHER THAN they both control how much air is going in by holding down the overall negative pressure in the firebox.... 8-)

So there ya have it, I hope you enjoyed my take on MPDs Baros and controlling heat lost up the chimney :funny:
Last edited by Lightning on Wed Jan 16, 2013 10:55 am, edited 4 times in total.
Lightning
 
Hand Fed Coal Furnace: Clayton 1537G
Coal Size/Type: Nut Size / White Ash

Re: Exhaust Heat

PostBy: joeq On: Tue Jan 15, 2013 8:50 pm

Thanx for that very in-depth explanation of the baro, lightning. And everyone else I appreciate your input. From all the opinions, whatever I take out of it will probably be so distorted, no-one will ever respond to another one of my threads.
So far, this is what I (might?) understand. A bigger stove will yield longer burn times with less maintenance. And a baro-damper will keep my drafts more constant. I'm assuming my question concerning heat going up the chimney is a non-issue, and "plugging"the pipe isn't doing me squat. As is setting a baro to a lesser setting in an attempt to "capture" heat. The manufacturer "highly" recommends a baro, and so does an individual I work with who stated his Surdiac stove ran flawlessly with one installed. Altho it does still elude me how my stove deficiencies will be resolved by a more consistent draft. Because the baro isn't too expensive or difficult to install, I guess I'll give one a try next season, just to say I've done everything recommended. Now if we would just get back to winter around here, I could fire up that thing again, and do some more tinkering. The daytime highs are suppose to drop below freezing in a day or 2. Maybe then it'll warrant it. Thanx a ton for your input people. :)
joeq
 
Hand Fed Coal Stove: Surdiac Gotha 513
Stove/Furnace Make: Oil fired
Stove/Furnace Model: Thermopride

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Re: Exhaust Heat

PostBy: Lightning On: Tue Jan 15, 2013 9:10 pm

joeq wrote:The manufacturer "highly" recommends a baro, and so does an individual I work with who stated his Surdiac stove ran flawlessly with one installed.


joeq wrote:And a baro-damper will keep my drafts more constant.


I have a baro on my furnace. Before I installed it, my furnace would not run steady. I would set the combustion air feed and it would steadily grow hotter as the chimney warmed up and drew harder it would continue to grow hotter.. A spiraling upward of heat until the chimney finally maxed out its ability to pull and my house was 80 degrees... So I would turn the combustion air feed down. Then it was a spiraling downward toward coolness as the chimney cooled it drew less which in turn would make the furnace continue to produce less heat and so on... There was no middle ground and I was sore from countless trips into the basement to adjust the combustion air.

Then the baro, and like magic - a steady regulated consistent outpouring of BTU's for 12 hours at a time - and I was much happier making less trips to the basement. This is the effect a baro has 8-)
Lightning
 
Hand Fed Coal Furnace: Clayton 1537G
Coal Size/Type: Nut Size / White Ash

Re: Exhaust Heat

PostBy: dcrane On: Tue Jan 15, 2013 10:20 pm

Lightning that was so well written i gotta give you props man :punk: Its one thing to have the knowledge of something but its a whole other animal to be able to convey that knowledge to others.

SO... after your well explained "take" on the subject, what do we do? :cry: (cough cough...lightning avoids that question like the plague) LOL

I think if you have poor-moderate draft you get a manual damper (in hopes you might actually need to control the poor draft someday, which you probably wont), i think if you have good-great draft you get the baro (thats my "take" in a nutshell) :P Every time i install a Barometric damper on a poorly drafting chimney EVERYTHING just sucks! sorry for being so blunt :cry:
dcrane
 
Hand Fed Coal Stove: Crane 404

Re: Exhaust Heat

PostBy: joeq On: Tue Jan 15, 2013 11:36 pm

Every time i install a Barometric damper on a poorly drafting chimney EVERYTHING just sucks! sorry for being so blunt :cry:[/quote]

:o Oh boy...more conflict. If I ever procured Barbra Eden in a bottle, and she offered me 1 wish, it wouldn't be a winning lottery ticket, or even Hugh Hefners currant girlfriend, but reliable 12 hr burn times, (with no fussing), from my newly installed Surdiac. Is that too much to ask for?
(Mr. Crane. I hope your head bobbing guy doesn't slip a disc. Looks pretty violent).
joeq
 
Hand Fed Coal Stove: Surdiac Gotha 513
Stove/Furnace Make: Oil fired
Stove/Furnace Model: Thermopride

Re: Exhaust Heat

PostBy: franco b On: Tue Jan 15, 2013 11:57 pm

joeq wrote: reliable 12 hr burn times, (with no fussing), from my newly installed Surdiac. Is that too much to ask for?

Your stove can do that now but only with low heat output. To raise the heat output with longer burning time the stove has to be altered. It needs a deeper bed in the fire box to hold more coal. That means raising the hopper at least an inch and to prevent coal from spilling out the front it also has to be raised by introducing a heavy piece of steel or by a cast refractory of furnace cement along the front edge of the fire box.

An alternative would be to take out the hopper and use the stove as a batch loader along with increased height along the front of the fire box. You might also have to do something on the sides if burning coal impinges there. You have to make the fire box deeper which is very easy to try.
franco b
 
Hand Fed Coal Stove: V ermont Castings 2310, Franco Belge 262
Baseburners & Antiques: Glenwood Modern Oak 114
Coal Size/Type: nut and pea

Re: Exhaust Heat

PostBy: Lightning On: Wed Jan 16, 2013 8:31 am

Yeah Franco is right I'm thinkin.. If you can't get a 12 hour burn because you are exhausting the coal load early, then its likely you need a bigger stove that will hold more coal OR modify the one you have to hold more coal.. In either case you need more coal :lol:

dcrane wrote:Lightning that was so well written i gotta give you props man Its one thing to have the knowledge of something but its a whole other animal to be able to convey that knowledge to others.

SO... after your well explained "take" on the subject, what do we do? (cough cough...lightning avoids that question like the plague) LOL


Thanks partner :D
I think its possible his stove is just too small for the area he is trying to heat.

dcrane wrote:I think if you have poor-moderate draft you get a manual damper (in hopes you might actually need to control the poor draft someday, which you probably wont), i think if you have good-great draft you get the baro (thats my "take" in a nutshell) Every time i install a Barometric damper on a poorly drafting chimney EVERYTHING just sucks! sorry for being so blunt


I agree, best case is to get the chimney to improve its draw if it has a poor draft.. An attempt to explain the possible scenarios that would improve the draw could require a several page thread.. The most obvious is to make sure the chimney is high enough, from there it gets kinda deep :lol: A baro only helps tame a draft thats too strong - it does little to nothing to help improve a weak one. I'm inclined to think it would make a weak draft worse since it always allows a tiny amount of air in the flue between the baro door and its housing there is at least a 1/16 inch gap around the baro door.
Lightning
 
Hand Fed Coal Furnace: Clayton 1537G
Coal Size/Type: Nut Size / White Ash

Re: Exhaust Heat

PostBy: titleist1 On: Wed Jan 16, 2013 10:52 am

Lightning wrote:
Lets say a gallon of air passes thru the combustion air opening in 5 seconds at .01" WC... Now, lets increase the negative draft pressure to a .03" WC and at the same time, we will reduce the combustion air setting so that the same amount (one gallon of air) passes thru it in the same amount of time (5 seconds). (IF this isn't reduced, more air will come thru the same size opening) What happened in 5 seconds in both these circumstances? A gallon of air entered the combustion air feed and a gallon of air + coal exhaust and some heat went up the chimney at two different pressures..

So there ya have it, :lol: I hope you enjoyed my take on MPDs Baros and controlling heat lost up the chimney :funny:



Good Write up and summary....just wanted to add one clarification which you touched on...
I agree, the baro doesn't "hold" heat in the stove, it keeps the coal from burning through too fast because all the air for the draft isn't coming through the coal bed. I like your gallon of air example...when keeping the same combustion air setting on the stove (i.e. spinner knob on ash door at same number of turns) when a baro is present will have maybe .7 gallon of air through the coal bed and .3 gallon through the baro. Obviously this % changes with the weather conditions.

I've never measured the draft with my manometer after the baro, but I suspect the reading should be higher (when the baro is open) than what i am getting at its current pre-baro position. Anyone ever do this?
titleist1
 
Hot Air Coal Stoker Stove: Harman Mag Stoker (old style) one in basement, one in workshop
Hand Fed Coal Stove: Harman Mark III on standby for long power outages
Coal Size/Type: Rice/Anthracite; Nut/Anthracite

Re: Exhaust Heat

PostBy: Lightning On: Wed Jan 16, 2013 11:04 am

titleist1 wrote:Good Write up and summary....just wanted to add one clarification which you touched on...
I agree, the baro doesn't "hold" heat in the stove, it keeps the coal from burning through too fast because all the air for the draft isn't coming through the coal bed. I like your gallon of air example...when keeping the same combustion air setting on the stove (i.e. spinner knob on ash door at same number of turns) when a baro is present will have maybe .7 gallon of air through the coal bed and .3 gallon through the baro. Obviously this % changes with the weather conditions.


Thank you sir 8-) Yes this is a good way to look at it as well, your perspective being after the baro..

titleist1 wrote:I've never measured the draft with my manometer after the baro, but I suspect the reading should be higher (when the baro is open) than what i am getting at its current pre-baro position. Anyone ever do this?


Actually, I would be almost ready to bet a pay check that the pressure reading is very close if not the same wheather the reading is taken before the baro or after it. I believe this since its the baro's job to maintain the negative pressure in the chimney.. With a MPD yes I would say definitely - the pressure is less before it and more after it. 8-)
Lightning
 
Hand Fed Coal Furnace: Clayton 1537G
Coal Size/Type: Nut Size / White Ash

Re: Exhaust Heat

PostBy: titleist1 On: Wed Jan 16, 2013 11:27 am

Lightning wrote:
Actually, I would be almost ready to bet a pay check that the pressure reading is very close if not the same wheather the reading is taken before the baro or after it. I believe this since its the baro's job to maintain the negative pressure in the chimney.. With a MPD yes I would say definitely - the pressure is less before it and more after it. 8-)


hmmmm.... :gee: I was thinking it would be higher after the baro since the baro being open adds more air to the exhaust than is present at the manometer tube before the baro. But maybe that is a volume versus pressure difference. Although if the pressure after the baro wasn't higher, then it wouldn't open. hmmmmmm......looks like I'm gonna have to try it sometime.....but I am not betting any paychecks!! :)

I do know that if I close the baro the manometer reading (before the baro) goes up versus when it is open!
titleist1
 
Hot Air Coal Stoker Stove: Harman Mag Stoker (old style) one in basement, one in workshop
Hand Fed Coal Stove: Harman Mark III on standby for long power outages
Coal Size/Type: Rice/Anthracite; Nut/Anthracite

Re: Exhaust Heat

PostBy: Rigar On: Wed Jan 16, 2013 5:35 pm

Take a drink thru a straw..
Now...
Put small hole in middle of straw...
Now take another drink...
Theres a difference....in pressure....HOWEVER
...this is NEGATIVE pressure... more commonly known as a vacuum
Rigar
 
Hot Air Coal Stoker Furnace: Keystoker A 150
Coal Size/Type: anthracite rice
Stove/Furnace Make: Keystoker
Stove/Furnace Model: A 150 warm air furnace

Re: Exhaust Heat

PostBy: Lightning On: Wed Jan 16, 2013 7:13 pm

Rigar wrote:Take a drink thru a straw..
Now...
Put small hole in middle of straw...
Now take another drink...
Theres a difference....in pressure....HOWEVER
...this is NEGATIVE pressure... more commonly known as a vacuum


I don't quite understand the analogy here partner :? The straw example your are comparing water to air? Also I thought it was a given that when referring to pressure in the firebox/flue/chimney would always be negative.. Am I blatantly missing your perspective?? Sorry if I am :lol:
Lightning
 
Hand Fed Coal Furnace: Clayton 1537G
Coal Size/Type: Nut Size / White Ash

Re: Exhaust Heat

PostBy: Chuck_Steak On: Wed Jan 16, 2013 8:21 pm

Lightning wrote:I don't quite understand the analogy here partner :? The straw example your are comparing water to air? ..
Am I blatantly missing your perspective?? ...


Yes you are, IIRC.
In the study of flow in physics, fluid dynamics refers to either
liquid or gas.
In other words, behavior when acted upon, are the same
for fluid, or gas..

Dan
Chuck_Steak
 
Coal Size/Type: mostly nut, sometimes stove, Santa brand
Stove/Furnace Make: Harman
Stove/Furnace Model: Mark III

Re: Exhaust Heat

PostBy: joeq On: Wed Jan 16, 2013 8:24 pm

franco b wrote:
joeq wrote: reliable 12 hr burn times, (with no fussing), from my newly installed Surdiac. Is that too much to ask for?

Your stove can do that now but only with low heat output. To raise the heat output with longer burning time the stove has to be altered. It needs a deeper bed in the fire box to hold more coal. That means raising the hopper at least an inch and to prevent coal from spilling out the front it also has to be raised by introducing a heavy piece of steel or by a cast refractory of furnace cement along the front edge of the fire box.

An alternative would be to take out the hopper and use the stove as a batch loader along with increased height along the front of the fire box. You might also have to do something on the sides if burning coal impinges there. You have to make the fire box deeper which is very easy to try.


Another intriguing idea FB. This I could try. However more coal means more air required to burn...right? I'm not sure about the different designs in fire boxes, but my intake damper is "below" the grates. When the coals burn, and makes ashes, the grates clog and the chokes off the air, which slows the burn down. If not addressed in 4-6 hrs, the fire goes out. When poked and scraped every 2-3 hrs, the stove makes more heat than the house needs, so it's not undersized.
I'll have to read the above posts on the baro. Lots of info. For now...gutta go. Suppertime.
joeq
 
Hand Fed Coal Stove: Surdiac Gotha 513
Stove/Furnace Make: Oil fired
Stove/Furnace Model: Thermopride

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