Over draft

Re: Over draft

PostBy: windyhill4.2 On: Mon Dec 16, 2013 10:17 am

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bucksnort wrote:I am having problems with my chimney drafting too hard and pulling the heat out of my stove and up the pipe. My chimney is a good bit above the ridge line of my roof and I live at the top of a hill without much around to break up the wind. All of this combines to cause an extremely strong draft. Last year I installed a barometric damper after not having luck with a manual pipe damper, and this and it made a big difference. However, the baro often stays wide open, especially when cold or windy, and I continue to lose a lot of heat up the flu. It's to the point where I hear it whistling up the pipe, causing me to have to burn much hotter than should be necessary to keep my house warm.

At this point I am considering two options: I've heard that installing a chimney cap can help with this problem, and I figure it wouldn't hurt to have a cap anyway, so I may try that. I've also considered installing a manual pipe damper in addition to the baro. Does anyone know either of these possible solutions would be adequate in reducing my heat loss? If I do put in an MPD, should it be between the baro and the chimney or between the baro and the stove? Any advice or other ideas would be appreciated!

The key point is .. the baro stays open 24/7, I'm no expert on chimney draft but I think this thread got side tracked. How will a bigger baro end this problem ? will the 8" pipe reduce the vacuum at the baro ? I'm asking because I do not know the answers to those 2 questions. Haven't seen any figures on what the actual draft figures are which would be the first step to correct this problem. If I understand the original problem correctly,it is not that the stove is overfireing from too much draft but that the baro is held open by too much draft, can baro be set "heavier"to overcome the draft? again I hope to learn more on the baro issue thru this,Thanks
windyhill4.2
 
Hand Fed Coal Stove: Crane 404 with variable blower
Other Heating: Oaktree OWB 600K

Re: Over draft

PostBy: Berlin On: Mon Dec 16, 2013 3:34 pm

A baro reduces draft the appliance sees by allowing a controlled amount of room air to enter the stack, this not only cools the flue thus reducing draft, but, breaks the draft to the appliance directly by allowing the flue to pull air from the room thus reducing vacuum in the flue.

A larger baro is necessary to break excessive draft because the ability to reduce the draft is directly related to the cross-sectional area of the baro's maximum opening. The change in pipe size has nothing to do with it, it's the size of the baro that's important. There's a forum member in niagara falls who went from about a 9" connecting pipe to something like 18" dia. T with a huge 18" baro and then back to 9" connecting pipe and to the stack. The stack was an interior stack over 40' high in a large old home in niagara falls and it still pulled that baro almost half open when the wind hit. When you have a situation with excessive draft, forget about mpd's + baro (you don't need it) all you need to do is use a large barometric damper to keep draft regulation automatic.
Berlin
 
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Re: Over draft

PostBy: titleist1 On: Mon Dec 16, 2013 4:30 pm

i read through this twice and i saw his stove temp listed at 450 - 500 but i didn't see his stack temp or manometer reading listed. did i miss it or are we still guessing?
titleist1
 
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Re: Over draft

PostBy: Lightning On: Mon Dec 16, 2013 4:59 pm

Would there be any down side to using an over sized barometric other than the added air infiltration?

I'm considering it.
Lightning
 
Hand Fed Coal Furnace: Clayton 1537G
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Re: Over draft

PostBy: windyhill4.2 On: Mon Dec 16, 2013 6:54 pm

So an open baro pulling room temp air is not a heat loss concern? but rather the stove temp exhausting at too high temp,so in this case he needs to lose more air via the baro to slow down heat loss from the stove ? Thanks,I'm still learning towards our future coal burning experience.
windyhill4.2
 
Hand Fed Coal Stove: Crane 404 with variable blower
Other Heating: Oaktree OWB 600K

Re: Over draft

PostBy: ridgeracing On: Mon Dec 16, 2013 9:44 pm

I am reading all this and it gets deeper than it needs to be.
1. Install manometer to get REAL draft reading.
2. If it is drafting to much and baro is opening up to much, install MPD as well, just have MPD 3/4 closed.
STOVE-MPD-BARO-FLUE
ridgeracing
 
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Re: Over draft

PostBy: bucksnort On: Mon Dec 16, 2013 9:45 pm

Unfortunately I am relying on magnetic thermometers as well. I put one on the stack this evening and am getting a reading of around 150. This is about and hour after shaking down the stove and adding coal. The stove temp was at around 550 at the time. However after reading the posts I'm not sure these things are very reliable. I also don't have a monometer but it seems I need to get one.

I guess now I'm confused on how my baro is working. I have the weight set at the mid point and the flap rarely ever closes. However if I adjust the weight heavier to make it close, the stove doesn't produce as much radiant heat. I assume this is because when closed the flu is pulling hot air off the stove and up the flu as opposed to pulling room temperature air from the room. Is this correct?

I have considered the sandstone basement walls are taking all the heat. But the walls seem sealed well with surface cement and the foundation is mostly underground. Its a pretty cozy basement really, I just don't see how it could absorb that amount of heat being its not very big. I also can't imagine I'm the only person with a stove in a basement that has a sandstone foundation...
bucksnort
 
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Re: Over draft

PostBy: fastcat On: Mon Dec 16, 2013 9:57 pm

Bucksnort there is NO way your stove is at 550* with 150* stack temps. You need to be giving us real numbers and these aren't real. :mad:
fastcat
 
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Re: Over draft

PostBy: warminmn On: Mon Dec 16, 2013 10:05 pm

Get a manometer first. Then as several have said if draft is high, add a MPD, or maybe the bigger baro. You cant trust those little numbers on the baro adjustment, at least not the one Im toying with and its the most recommended one, a new Field RC. You need a manometer, you cant guess. They are kind of fun to look at anyway.
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Re: Over draft

PostBy: bucksnort On: Mon Dec 16, 2013 10:17 pm

fastcat wrote:Bucksnort there is NO way your stove is at 550* with 150* stack temps. You need to be giving us real numbers and these aren't real. :mad:
You really think I'm making up these temps?? That's what the magnetic gauge says. I can read. I came for advice, not to be insulted... sorry for asking questions, I'm not very experience
bucksnort
 
Hand Fed Coal Stove: DS Machine Basement #4
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Re: Over draft

PostBy: ridgeracing On: Mon Dec 16, 2013 10:33 pm

I dont think he ment offense to your figures, He is just saying that with a stove temp of 550 you wont have a chimney stove pipe of temp of 150. One or both of your guages may be out of wack? I believe my chimney at that stove temp is like 250-300 roughly. To make that much heat, you will loose a good bit up the chimney no matter what.
PS- I got my manometer at GRAINGERS for less than $47.00 ( Dwyer Mark II model 25)
ridgeracing
 
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Re: Over draft

PostBy: bucksnort On: Mon Dec 16, 2013 10:44 pm

Is there a better way to get a more reliable reading? I placed the magnetic gauge on the pipe between the baro and the section that goes to the chimney entrance. Also I think from what I've read here, a monometer is going to be important in understanding if I truly have a real draft problem.
bucksnort
 
Hand Fed Coal Stove: DS Machine Basement #4
Coal Size/Type: Hard Nut Coal
Stove/Furnace Make: DS Machine
Stove/Furnace Model: Basement #4

Re: Over draft

PostBy: Rob R. On: Mon Dec 16, 2013 10:45 pm

bucksnort wrote:I placed the magnetic gauge on the pipe between the baro and the section that goes to the chimney entrance.


The air brought through the baro cools the flue gasses. Move the thermometer between the baro and the stove.
Rob R.
 
Stoker Coal Boiler: EFM DF520
Hand Fed Coal Stove: Hitzer 50-93
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Re: Over draft

PostBy: Sunny Boy On: Mon Dec 16, 2013 11:06 pm

fastcat wrote:Bucksnort there is NO way your stove is at 550* with 150* stack temps. You need to be giving us real numbers and these aren't real. :mad:



Real ?
If you mean a coal stove can't have that much difference in stove to stack temp, . . . says who ? My stove typically runs 650 to 700 at it's hottest end top plates and only 130-140 stack temps measured 36 inches up on the stack from the stove top with both a bimetallic magnetic gauge and an IR hand-held test gauge, . . which are within a few degrees of each other, and when tested against the freezing and boiling points of water, are within a few degrees of "real".

Each stove, each chimney, and each location unto it's own ! :)

Paul
Last edited by Sunny Boy on Mon Dec 16, 2013 11:16 pm, edited 1 time in total.
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Re: Over draft

PostBy: bucksnort On: Mon Dec 16, 2013 11:10 pm

Moved the gauge between the stove and the baro and gave it about 10 minutes to adjust. Looks to be around 225 with the stove still at 550. I ordered the Dwyer manometer online tonight. When it gets here and I get it installed I'll get some readings on here. Thanks for all the suggestions
bucksnort
 
Hand Fed Coal Stove: DS Machine Basement #4
Coal Size/Type: Hard Nut Coal
Stove/Furnace Make: DS Machine
Stove/Furnace Model: Basement #4

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