Stainless Steel All Fuel Chimney for Coal Use

 
janitor_ed
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Post by janitor_ed » Sat. Sep. 22, 2018 7:02 am

I'm considering installing an all fuel class A stainless steel triple wall chimney. I am aware of the corrosive nature of the byproducts from burning coal but I figure if I can get 3 to 5 years out of it, then I'm ok with that. Are there other considerations?

Also I see a lot of stokers recommend to use an 8 inch or 9 inch flue. Is there really an issue with using a 6 inch flue if it provides sufficient draft?

Any opinions?


 
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Rob R.
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Post by Rob R. » Sat. Sep. 22, 2018 7:19 am

A 6" flue will not be adequate for your stoker boiler.

 
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Post by janitor_ed » Sat. Sep. 22, 2018 8:27 am

Rob R. wrote:
Sat. Sep. 22, 2018 7:19 am
A 6" flue will not be adequate for your stoker boiler.
Hi Rob,

I don't doubt your wisdom on this subject but I'm curious about the dynamics that in play here. Could you elaborate a bit further or point me to where I might find additional info?

Best Regards,
Ed

 
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Post by StokerDon » Sat. Sep. 22, 2018 8:31 am

As you say, "If it supplies sufficient draft". At full fire on a cold day, 6" will likely cause your firebox draft to go positive because it can't supply enough draft.

Triple wall????
The only triple wall that I know of is not insulated. It uses an air gap to reduce the temperature to combustibles. This will not work because when the stoker idles, it puts very little heat into the chimney. An un-insulated SS chimney will loss draft at idle. Any metal chimney on a coal stoker needs to be insulated.

-Don

 
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Rob R.
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Post by Rob R. » Sat. Sep. 22, 2018 8:59 am

janitor_ed wrote:
Sat. Sep. 22, 2018 8:27 am
Hi Rob,

I don't doubt your wisdom on this subject but I'm curious about the dynamics that in play here. Could you elaborate a bit further or point me to where I might find additional info?

Best Regards,
Ed
Ed, the stoker on your Gentleman Janitor is quite a bit larger than the ones that are made to work with a 6" flue. If the chimney is tall enough, if it drafts well, and if you do not run the stoker more than the minimum feed rate, 6" would probably be fine...but that is a lot of if's, and coal combustion gases are not something you want in your house.

I have hooked up an EFM with a 6" chimney, and even on the lowest stoker setting the firebox was on the edge of going positive. Just too much resistance on the exhaust side. Considering the amount of air that GJ stoker is going to move, I think 6" would be marginal at best for your boiler.

 
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Post by coaledsweat » Sat. Sep. 22, 2018 2:24 pm

The exhaust gases want to expand so you want the chimney bigger than the appliance's breech.

 
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Post by janitor_ed » Sat. Sep. 22, 2018 7:34 pm

StokerDon wrote:
Sat. Sep. 22, 2018 8:31 am
As you say, "If it supplies sufficient draft". At full fire on a cold day, 6" will likely cause your firebox draft to go positive because it can't supply enough draft.

Triple wall????
The only triple wall that I know of is not insulated. It uses an air gap to reduce the temperature to combustibles. This will not work because when the stoker idles, it puts very little heat into the chimney. An un-insulated SS chimney will loss draft at idle. Any metal chimney on a coal stoker needs to be insulated.

-Don
Hi Don,

Yep, triple wall and insulated. The product that I have been looking at is called DuraPlus and can be found here http://www.duravent.com/Product.aspx?hProduct=2 This pipe does come in an 8" flue size but the price per section seems to be about 3X more costly.

Honestly, I'd like to do a block Chimney but I'm not sure that I have the kind of time to do one. Also, I've never put up masonry chimney before so I'm a bit on edge about doing it. To be honest I'm generally pretty much handy at most things and could probably do fine with it. Perhaps I can find a mentor to give me a bit of guidance on this.

Best Regards,
Ed


 
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Post by janitor_ed » Sat. Sep. 22, 2018 7:44 pm

Rob R. wrote:
Sat. Sep. 22, 2018 8:59 am
...but that is a lot of if's, and coal combustion gases are not something you want in your house.
Agreed!
Rob R. wrote:
Sat. Sep. 22, 2018 8:59 am
I have hooked up an EFM with a 6" chimney, and even on the lowest stoker setting the firebox was on the edge of going positive. Just too much resistance on the exhaust side. Considering the amount of air that GJ stoker is going to move, I think 6" would be marginal at best for your boiler.
Ok. Thanks to you and Don I now have a better understanding of the potential issues. Don's comment about what happens at idle really jogged my brain a bit because honestly, i wasn't thinking about it not running full bore-full time. LOL! What a noob I am! Your comment about the amount of air the GJ is going to move also helped and while I was thinking "resistance" with the 6 inch flue in the back of my brain, I just couldn't get that to come to the forefront for some reason.

Best Regards,
Ed

 
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Post by StokerDon » Sat. Sep. 22, 2018 8:15 pm

The draft at idle is something that wood burners and hand fired coal burners don't have to deal with, so it is hard to get your head around at first. The fire pretty much goes out on a stoker when it idles. The draft and the timer are the only thing that keep it alive.

-Don

 
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Post by coaledsweat » Sat. Sep. 22, 2018 9:20 pm

Build the masonry chimney.

 
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Post by Qtown1835 » Sun. Sep. 23, 2018 6:32 am

coaledsweat wrote:
Sat. Sep. 22, 2018 9:20 pm
Build the masonry chimney.
∆∆∆What he said

 
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Post by janitor_ed » Wed. Sep. 26, 2018 10:05 pm

Continuing the discussion... The data that Don kindly posted about the GJ says recommended chimney length of 19 feet with an 8 inch flue. Based on previous comments it seems that an 8 inch flue would be the minimum recommended.

Would a 10 inch flue be even better? I wonder how much this would affect the length? Does anyone know if there is a simple formula that can be applied?

 
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Post by McGiever » Wed. Sep. 26, 2018 11:44 pm

10" flue will move more volume of air but will not incrementally increase the draft value at equal heights...only increased height can render increased draft, however the 8 inch flue diameter can remain the same to accomplish this increased value.

There are other gains besides increased draft by building a taller chimney/flue.
Higher chimneys are far less to even never effected by down drafts.

Look at some chimney details with Goggle...

 
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Post by lzaharis » Thu. Sep. 27, 2018 9:31 am

I had days when the draft went positive and I had a smurf with a flame thrower blowing a 2 foot blue flame coming out of the lower draft door on my hand fed so you need a big chimney. If the smurf had turned the gas up on the flame thrower it would have caught the opposite wall on fire for sure.

 
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Post by StokerDon » Thu. Sep. 27, 2018 6:18 pm

janitor_ed wrote:
Sat. Sep. 22, 2018 7:34 pm
Yep, triple wall and insulated. The product that I have been looking at is called DuraPlus and can be found here http://www.duravent.com/Product.aspx?hProduct=2 This pipe does come in an 8" flue size but the price per section seems to be about 3X more costly.
This type of pipe has features that are completely unnecessary for a coal stoker boiler. The air gap is there to give more clearance to combustibles, this is great if you have 1000 degree flue gasses (wood). Your GJ will rarely ever get above 400. Also, the air gap will likely cool the inside of the chimney which will in turn really hurt the idle draft.

It also states that the second wall is galvanized steel, not stainless. Once fly ash and moisture get onto the galvanized, it won't last long.

If this product costs more than their double wall insulated pipe, I would definitely not use it. The double wall is stainless inside and out and works very well.

-Don


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