Heating Help

Power Gas Burner and Flue Dimensions

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I'm engineering to put in a new Slant-Fin Intrepid or Smith G8 boiler with a Power Gas Burner; before this winter starts.
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I need to get the chimney lined though.  Do I use the same specs for chimney size as stated by the manufacturer for oil, OR do I need to go larger or smaller because of the power gas burner. 
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my other question is:  when the chimney IBR rating says 8"x8"x15' rectangle or 6"x15' round, do i need to size up for a 40 foot length?
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Thanks.  I'm sure the chimney guy could answer my questions, but i figured i'd ask anyway in case he doesn't.  :-)
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Tom in Conshohocken.PA

it is based on

btu's to be vented, so same as required for oil or gas. The diameter is inverse to the height but has to be a minimum size no matter how tall the chimney gets. The liner company should have charts from their liner manufacter to use if they do not have a local code book. Codes vary and I do not know which is used in your area. The size is also based on winter air temps for your region.

thanks charlie

a BTU is a BTU.  I knew that, but wasn't totally sure.  Thanks Charlie, your the man.
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I bought my grandmom's house, and she put in an oil fired boiler with a power vent.  We're not sure if the chimney is collapsed inside and can't be lined, or if she didn't have the money, and a power vent was cheaper. 
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I want to put a porch on the side of the house, and the power vent vents right where I want to put the porch, and that isn't code.  Also, the power vent is friggin loud!  I have enough things failing in the house to worry about the power vent dying on Christmas day. 
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We'll see, i have some chimney companies coming for quotes, and that will determine which boiler type to get.  Wish me luck that the chimney isn't collapsed. 

-Tom in Conshohocken

thanks charlie

duplicate

You could remove the old chimney

and replace with an all fuel stainless steel chimney in the same chase. Also If you go gas fired Burnham has the Independence pv series that can vent out the side wall. Just a couple ideas.

bad news

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Well, chimney guy #1 said that the largest round he could fit would be about 4", (and that's squishing it into an oval).  I guess i had a small chimney to begin with, and California terracotta was installed, and now it's really small.  At least it's not collapsed inside.  I guess Grandma put in a power vent because the chimney was too small to line. 
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I talked to the tech guy at Slant-Fin, and he said spec was 6"x15' for a round liner.  He said if i have 30 ft of height, i could go to 5" round diameter.  (for the TR-30 model).
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I'd really hate to go power vent, because i'm still planning on putting a porch on that side of the house.  And a B vent would ruin my fancy Victorian exterior. :-)
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I also found out the Smith G8 direct vent model is not approved for a power burner.  FWIW.
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Anyway, so what's the equation?  Is there an armchair calculation for chimney size per BTU and height?  I didn't see anything online, and I don't have a NFPA book. 
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Thanks!

Power vent

I think you could power vent in the chimney, it was one option I had to deal with since the chimney is for natural draft, power venting up in the chimney could be an option, something to ask slant-fin, keep in mind I'm just a home owner

How large of a boiler do you need?

have you measured your radiators yet for square footage? start at the begining and we can go from there.

remove the tile liner

Did your chimney guy talk about removing the existing terracotta liner to gain more space in the chimney? That might be an option - when I looked into relining my fireplace that's what both guys suggested.

Wow

And here I thought I was all alone!

Last October I had my brick chimney torn down and replaced with a 6 inch B-vent because of the same problem.  Mine had something like a 4x6" opening and the chimney guys did everything they could to try and line it and finally gave up.

We did a lot of talking and decided the best thing for me was to tear the chimney down and run a B-vent in its place. I decided against power venting because no one could promise me how well it would work and I didn't want the noise.  Several people also told me power vents for this are installed outside and work 100% by suction so it didn't sound like it would work.

Notice the size of the unlined opening next to the guys hand.  I took this while he was carefully vacuuming and unstacking the bricks.  I suspect this chimney was built when the house was half the size and heated by 3 wood stoves.  Throughout the years they added several additions and then steam heat and expected the same chimney to handle the load. 


That said, I ended up reading some charts like this.  Its not necessarily exact for whatever vent or liner you are going to install, but it gives you an idea.

http://www.hartandcooley.com/Libraries/Product_Literature/Hart_Cooley_Type_B_Gas_Vent_All-Fuel_Chimney_Sizing_Guide.sflb.ashx

mine's the same

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Chris J.-  Mine's the same size.  Looks like they made it by using five bricks for each layer, and the inside dimensions turn out to be the same size as 1 brick.  Mine is lined in terra-cotta and is even smaller.  It seems pretty common in my neighborhood apparently.   hey that .pdf is some really good info.  printed it out and put it in the filing cabinet anyway. 
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Power vent or Direct Vent are the only options.   getting that porch on that side of the house might require 'executive dispensation' from the code inspector.   
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Charlie-  I have 239 sq ft EDR.  not including pickup factor.  They removed a lot of the radiators throughout the years apparently, but the house heats well.  My current oil boiler is sized to 469 sq ft!  go figure.  I also have an unheated addition (not my design!) that I would like to heat with a radiant wall using hot water loop and heat exchanger.  That's later down the line though.  Once the wife gets her new kitchen.  (in about 15 years :-))
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I don't see that anybody makes any gas steamers that are direct vent.  I called slant-fin and Smith about their Intrepid and G series direct vent models, they're not approved for power gas burners.  I dont even see any traditional gas steamers that are direct vent.  Direct vent is plan B, and power vent is plan C.
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Thoughts?

Burnham

Independence PV series can vent through the wall. It is not wet base, but it is still quite efficient. that small of a boiler the 2 percent savings going wet base may not pay baqck that soon.

105K btu input

It looks like an IN4 would cover your steam load and its only 105K btu input which a 4" flue will handle at 30 feet.

Now you said yours has a clay liner installed so its even smaller, maybe 3"?

Question is what size is it in the other direction and can you find a rectangle liner to fit it, and is it possible to install. My chimney was special in that in the attic I had an offset where it went over a few feet to line up with the center of the house. At that offset they rebuilt it and made a square opening so a rectangular liner would have never worked for me not to mention my boiler is 150K input.

Maybe it can for you?

thanks-

Awesome guys!  thanks.  That's why i hang out here.  I didn't know that anybody offered an integral power vent gas steamer.
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now if it only came with an outside air intake :-)
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is that the only one on the market?  looks like it.
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Tom in Conshohocken Pa
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