# Double or Triple wall chimney pipe



## Ol Yeller

I just installed a new PSG caddy Furnace in my upstate NY home.  it was working well. For safety reasons, I hired a chimney sweep to inspect a few concerns I had regarding the chimney as well as WC pressure.  This is our first experience delving into wood burning other than using our fireplace occasionally.
    The professional said the chimney was looking great, but we had -.01 for wc.  The Caddyy calls for -.02 to -.06.  We were way to far from our chimney, 17 horizontal feet, which is what it had been prior for our oil furnance.  No where in the manual or elsewhere had I read any info on the maximum horizontal length, otherwise I would have not proceeded with plans.  After a call to PSG, the tech said it cannot exceed 7 feet.  After taking time to dig out 432 cubit ft of dirt, stone & bedrock from a crawl space in my 1811 home, I determined it was better for plan B. We could not get any closer to our existing furnance. 
     So I decided to move it closer to an outside wall an build a chimney.  Through various sources, I hear controversial thoughts about whether to use insulated double wall pipe or more expensive triple wall pipe.  The horizontal run will be about 5 feet and vertical height will be about 17 ft.  The chimney will be outside of a wall and gabled roof. Because I am concerned about safety issues and chimney fires, I wanted t make sure I do the right thing and all this stuff is outside my expertise.  It seems like its already been a long winter, lol.  
   Which do I use, triple or double?  And... will he insurance companies look for something specific?   Thanks for your help and generosity.


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## lotawood

I don't know about your caddy, but single wall and double wall is stove pipe for the inside of a structure.  Triple wall is double wall with a insulating blanket.  Triple wall is class A chimney pipe, usually satisfies code requirements for clearance from combustibles at penetration, and the rest of the way from there on.  You want the smoke and gasses to be as hot as possible when it hits the rain cap to prevent build up on the inside and the draw is better.
I try not to have a horizontal run of pipe, especially single wall.  I do have single wall at a mild angle, might be 30 degrees, tapering back to a wood stove. It is 12 feet supported in the middle.  I think I would clean it way more often if it was straight horizontal.  There was another thread on a wood gun boiler with stove pipe at an angle run replacing a long horizontal,  which he felt was an improvement.


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## Ol Yeller

Thank you. 
12' of the horizontal pipe had a 20% incline, but still not enough draft and caused liquid creosote to find its way onto the floor at one spot.
I believe it's a language barrier.  I didn't realize triple wall was double wall with an insulated wall in between.  I thought it was 3 separate steel walls with no insulation, just the two air spaces acting as insulation.


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## heaterman

Either double wall insulated or triple wall can be rated for Class A use....which is something on the order of around 2000* for a specified amount of time. In your case I would probably recommend the double wall insulated because I think it would keep the flue a little warmer in an outdoor application. Letting the flue get below about 300* is going to create a mess due to condensation.


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## lotawood

I just noticed this is your first day, welcome to the forum. 
If you are getting drips of creosote on your floor you might make sure your pipe has the crimps in the right direction.  The higher pieces should funnel any liquid into the next lower pipe. Single wall pipe is cheap to make changes to.  The other not so much.  Class A is expensive to have plan B.
Also insurance works best to be brought in the loop before money is spent.  Call them up and ask first. Since you mention it might be outside your expertise,  getting contractor experienced in chimney pipe installation might be money well spent.  I did that on the first chimney install that happened on my watch. I asked questions and learned.  You will know when you know what you are doing, you know.


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## BoilerMan

I believe triple wall is not insulated, the stuff they sell at TSC up here is triple wall and is cheaper than the more conventional double wall insulated.  Class A means 2100 degrees F for 20min, and the combustibles with the two inch clearance can't get over a certain temp.  Bottom line, insulated double wall like, Selkirk, Excel, Simpson etc, are all used for wood-burning and hold up well over the long run and keep the flue as hot as possible for good drafting and the least creosote formation.

TS


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## laynes69

We use a Caddy, and there's a couple of things you will find with the furnace. One is they require good seasoned wood, and two good draft. How long has your wood been cut and stacked? We had problems initially with condensation also, but our flue was too big in our chimney and wood that was less than seasoned. We put in an insulated rigid stainless liner and have changed our habits in wood collection and things are fine.


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## Ol Yeller

thanks.  We thought plan B was more expensive (Class A Chimney) until we found that removing the crawl space and bedrock was much more labor intensive than we were hoping.

The single wall does have the crimped ends facing the furnace.  It only leaks on the flat part. It shouldn't be an issue once I move the furnace to the new location.
I'll call the insurance company.


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## Ol Yeller

laynes69 said:


> We use a Caddy, and there's a couple of things you will find with the furnace. One is they require good seasoned wood, and two good draft. How long has your wood been cut and stacked? We had problems initially with condensation also, but our flue was too big in our chimney and wood that was less than seasoned. We put in an insulated rigid stainless liner and have changed our habits in wood collection and things are fine.


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## DexterDay

Taylor Sutherland said:


> I believe triple wall is not insulated, the stuff they sell at TSC up here is triple wall and is cheaper than the more conventional double wall insulated.  Class A means 2100 degrees F for 20min, and the combustibles with the two inch clearance can't get over a certain temp.  Bottom line, insulated double wall like, Selkirk, Excel, Simpson etc, are all used for wood-burning and hold up well over the long run and keep the flue as hot as possible for good drafting and the least creosote formation.
> 
> TS


Depends on the brand. All Double wall (Class A) is insulated and some Triple wall is insulated. 

Some Triple wall Class A is Air cooled, but there are brands that do have insulation
 My Simpson is insulated Class A Triple wall. 

To the OP- Please dont confuse Double wall stove pipe (inside) with Double wall Class A (external/internal) pipe.


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## Ol Yeller

well... because I was late in getting this system moving forward, I had 10 cord delivered so far from a retired gentleman who said he split last years logs back in June/July. 

Speaking of flue sizes, the older chimney is a multi flue with two measuring 6x11 inch.  Maybe that was an issue to, not to mention the furnace never really got that hot because we never really needed that much heat with moderate temps.


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## BoilerMan

DexterDay, now that you mention it, I've seen the insulated triple wall. Required for factory built fireplaces. The airspace is used for combustion air to the apliance.

TS


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## laynes69

Yeah, you are dealing with unseasoned wood. It should be split and stacked for a year, and oak for 2 years. Our old chimney flue was 11x7 or so, it caused many problems. The furnaces are very efficient and there just wasn't enough heat to keep the old chimney warm, hence the condensation.


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## Ol Yeller

laynes69 said:


> Yeah, you are dealing with unseasoned wood. It should be split and stacked for a year, and oak for 2 years. Our old chimney flue was 11x7 or so, it caused many problems. The furnaces are very efficient and there just wasn't enough heat to keep the old chimney warm, hence the condensation.



That makes since.  Good to know about the true definition of seasoned wood.  My plan has been to get extra now in order to try and get ahead of it.  Any suggestions of what I should do in the meantime? I just soon keep the caddy since I only paid $1200 for it new.


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