chimney size ?

chimney size ?

PostBy: biggreen1 On: Tue Jul 01, 2008 10:23 pm

Well, My boiler is now going out to the garage again so I have a chimney question. I've got a AA130 coming and in the instruction manual it calls for a 8"X8" flue 15' high. Where I'm thinking of building the flue it may only need to be 11' or 12' tall. Should I stick with 8"X8" or go up to a 12"X12". I've never built a chimney before so now I have another thing to learn how to do(is't life fun). My guess is that I'd be fine with a 8", but are there any advantages of going larger? Thank you. BG
biggreen1
 

Re: chimney size ?

PostBy: coalkirk On: Tue Jul 01, 2008 10:34 pm

Better to stick to the 8x8 and go the full 15'. A larger flue will reduce your draft, not good with coal. Also taller is better for draft.
coalkirk
 
Stoker Coal Boiler: Harman VF3000
Coal Size/Type: antrhcite/rice coal

Re: chimney size ?

PostBy: biggreen1 On: Tue Jul 01, 2008 10:55 pm

If I go up 15', the chimney will be over the lower edge of the roof about 7'. That doesn't sound right to me, but what do I know.
biggreen1
 


Re: chimney size ?

PostBy: LsFarm On: Tue Jul 01, 2008 10:58 pm

The 15' height will provide the .02-.04" wc draft that AA is looking for when the boiler is idling.. I have about 15' of 8" chimney, and it is providing about .02"wc of draft.. I'm not sure that 12' would be tall enough..

Greg L.

.
LsFarm
 
Stoker Coal Boiler: Axeman Anderson 260
Hand Fed Coal Boiler: Self-built 'Big Bertha' SS Boiler
Baseburners & Antiques: Keystone 11, Art Garland

Re: chimney size ?

PostBy: biggreen1 On: Tue Jul 01, 2008 11:37 pm

LSfarm,
Aren't you using a AA260? Mine will only be a 130.
biggreen1
 

Re: chimney size ?

PostBy: Freddy On: Wed Jul 02, 2008 5:39 am

The height in the book would be the minimum height. They are looking to make proper draft. I'd stay with the 8", same reason.
Freddy
 
Stoker Coal Boiler: Axeman Anderson 130 (pea)
Hot Air Coal Stoker Stove: Reading piece o' junk in the barn (rice)
Coal Size/Type: Pea size, Superior, deep mined

Re: chimney size ?

PostBy: LsFarm On: Wed Jul 02, 2008 8:30 am

The minimum draft called for by Axeman Anderson does not differ from model to model.. the minimum draft is required so that the chimney will draw the fumes and exhaust off the top of the fire when the inspection port is open, this is when the boiler is idling..
Once the boiler is in the run cycle.. the combustion fan pulls the inspection door shut, and pulls combustion air up through the coal bed and forces the exhaust through the heat exchanger, and out and up the flue pipe..

The chimney on my setup will drop from .02-.03"wc to near zero or .01"wc for a second or two when the combustion fan first starts, but almost imediately it will increase to .04"wc, and draft well.. The heat forced up the chimney creates an almost instant draft.. If the wind is blowing strong, I can see ocassional readings of .07" or so, but the barometric damper keeps it from going higher.

Greg L..
LsFarm
 
Stoker Coal Boiler: Axeman Anderson 260
Hand Fed Coal Boiler: Self-built 'Big Bertha' SS Boiler
Baseburners & Antiques: Keystone 11, Art Garland

Re: chimney size ?

PostBy: biggreen1 On: Wed Jul 02, 2008 8:37 pm

Ok, I know I'm just hoping here. Do you start the height measurement from where the flue pipe enters the chimney or where it leaves the top of the boiler?
biggreen1
 

Re: chimney size ?

PostBy: LsFarm On: Wed Jul 02, 2008 9:50 pm

You should start the measuring where the flue pipe enters the chimney.... If you are willing to not finish the top of the chimney, make it the height you want, and see if it draws well enough.. if not, then add several more feet to the chimney... you can build it in stages..

One thing in your favor is the fact that the boiler is going into the garage,, not the house... is the garage detached, or at least well separated from the house with well sealed doors??? If the chimney doesn't draft real well, lets say marginal like mine is [.02"wc] it still won't be a safety hazard in the garage.
I'd still keep a funcional CO alarm in the garage.

Greg L.

.
LsFarm
 
Stoker Coal Boiler: Axeman Anderson 260
Hand Fed Coal Boiler: Self-built 'Big Bertha' SS Boiler
Baseburners & Antiques: Keystone 11, Art Garland

Re: chimney size ?

PostBy: biggreen1 On: Wed Jul 02, 2008 10:19 pm

Yes the garage is about 35' from the house, totally detached. Not finishing the top is a good idea. As long as it's structurally sound to have the chimney 6-7' up from the lower edge of the roof I probably should just finish it and be done with it. Thanks for the help
biggreen1
 

Re: chimney size ?

PostBy: biggreen1 On: Sat Jul 05, 2008 10:05 pm

There is a slight chance I may try and heat another building in the future (maybe 10 years down the road) that is about 75 feet from the garage where the boiler is going. It's a rather large building so I don't think the AA130 would be up to the job of doing it all. I noticed that the AA260 requires a 12" flue. What do any of you think about putting up a 12" chimney and then adding a SS liner to reduce it down to 8" to get the proper draft for the AA130? Also, I noticed that the EFM only needs a 8" flue even though it can put out about the same BTU's as a AA260, Can anyone explain that?
biggreen1
 

Re: chimney size ?

PostBy: LsFarm On: Sat Jul 05, 2008 10:54 pm

The AA manual may say a 12" flue, but my AA260 works just fine with an 8x8" inside dimension flue... I really don't think you need more.. I'd put up a block chimney with the square terracotta liner with inside dimensions of 8x8",, and as tall as you can feel comfortable with.. I put up my own block chimney,, I was standing in the front bucket of my loader-tractor for the last few block,, and I was feeling my age the next morning !! but the chimney is nice and straight and works great too...

The AA boilers with their forced draft design only need natural draft for the time when the boiler's fire is idling.. once the combustion fan starts up,, there is a very significant forced draft that very quickly heats the chimney and you have a strong natural draft along with the fan-forced exhaust.. i wouldn't be concerned about a bigger size flue.. maybe a taller one, but 8x8 should be plenty..

Greg L
.
LsFarm
 
Stoker Coal Boiler: Axeman Anderson 260
Hand Fed Coal Boiler: Self-built 'Big Bertha' SS Boiler
Baseburners & Antiques: Keystone 11, Art Garland

Re: chimney size ?

PostBy: biggreen1 On: Sun Jul 06, 2008 12:11 am

LsFarm, You just made my day. Thank you for that information
biggreen1
 

Re: chimney size ?

PostBy: LsFarm On: Sun Jul 06, 2008 8:15 am

HI BG, I forgot to mention, your AA130 likes to work,, I probably could get by with an AA 130 on my farm, but I found the AA260 first. So I'll be surprised if you need to upgrade the boiler when/if you add on some additional heat loads,, unless they are huge loads..

There is a guy in central PA that a fellow member has visited that runs about 20-24 tons of coal through an AA260 a year,, that's double my use... We also have a forum member who heats several houses and apartments with a 130, it runs almost continously in the cold months.. but these boilers like to work, they are the most efficient when near capacity..

And by changing your fan drive pulleys, you can speed up the fan a little and increase the BTu output some if needed..

So unless you are adding a 6000 sqft greenhouse :D , your AA130 will probably carry the load.. a very general statement, but quite likely accurate.

Greg L
LsFarm
 
Stoker Coal Boiler: Axeman Anderson 260
Hand Fed Coal Boiler: Self-built 'Big Bertha' SS Boiler
Baseburners & Antiques: Keystone 11, Art Garland

Re: chimney size ?

PostBy: Yanche On: Sun Jul 06, 2008 11:53 am

biggreen1 wrote:There is a slight chance I may try and heat another building in the future (maybe 10 years down the road) that is about 75 feet from the garage where the boiler is going. It's a rather large building so I don't think the AA130 would be up to the job of doing it all. I noticed that the AA260 requires a 12" flue. What do any of you think about putting up a 12" chimney and then adding a SS liner to reduce it down to 8" to get the proper draft for the AA130? Also, I noticed that the EFM only needs a 8" flue even though it can put out about the same BTU's as a AA260, Can anyone explain that?
Stay with the AA 130. As GregL has said it likes to work. If it's inadequate to heat your building, insulate the building better or supplement it with another boiler that only runs when needed.
Yanche
 
Stoker Coal Boiler: Alternate Heating Systems S-130
Coal Size/Type: Anthracite Pea