stove pipe ??

[alternativeheat]

As long as the transition is a safe connection, I don't see the problem.
I think there would be more of a problem if you ran 3" up a long way..

Well unless I read it wrong ( and I have done that before) I believe the OP stated that his manual says not to expand more than to 6", which is fairly typical for more than one pellet stove brand. He can listen to a forum member who states he doesn't think it's an issue if he likes , that would be his business. But my suggestion would be to follow the manual.

I do agree that he must be on the limit or even over for 3" pipe though. The standard pretty much in the industry is that if 3" will be restrictive because of over length, then go to 4". This offers the flow but keeps the exhaust gasses nice and hot. You don't want to expand the gasses and lose heat, that can cause creosote.

 

[Highbeam]

So the class A 8" or 6" is designed to be a chimney with a negative pressure or draft sucking on it. With the pressurized exhaust from a pellet stove, is there not a worry about leakage at the joints of class A? Up in the attic that is?

 

[unclebobsjerky]

OK here's what i found out the total length of this install is a little over 14 feet.
1: from the back of the new stove to the new 8 inch to 3 inch adapter is 7 feet 2 inches
2: from the attic floor to the chimney cap is 7 ft 7 inches of Duravent Class A chimney.
I talked to a support rep from the stove company gave him all the figures and he told me that with only a 7 ft run of a larger sized pipe it will cause no problem in terms of venting the pellet stove and that he was confidant there will be no heat issues because of the class A Duravent system.
I asked about the possibility of a fly ash buildup where the stove pipe and adapter meet . his answer was first off if we are talking about fly ash it has already had its primary burn and at the point of build up there is no more fuel to ignite therefore the only worry would be creosote build up which would be negligible if the proper maintenance and cleanings were followed

 

[unclebobsjerky]

So the class A 8" or 6" is designed to be a chimney with a negative pressure or draft sucking on it. With the pressurized exhaust from a pellet stove, is there not a worry about leakage at the joints of class A? Up in the attic that is?

maybe, I will have to keep an eye out for that. the stove pipe in the attic is on the very edge of the eve but still on the inside of the house. there is 30 inches of class A and the only connection is where it connects to the ceiling adapter from the floor below

 

[alternativeheat]

Yeah, ash isn't a fire hazard in itself, it's just messy. It can lead to secondary issues with the stove as well. But your 8" will plug long after the 3", it should be a very free flowing vent.

So you're good to go according to that rep then.

 

[unclebobsjerky]

this all has yet to be seen but the larger of the two pipes is only a little over 7 ft to the cap.i will be burning the stove many many times this summer just to have peace of mind come winter.........

 

[Pete Zahria]

He can listen to a forum member who states he doesn't think it's an issue if he likes , that would be his business.

I couldn't agree with you more.
That is strictly my opinion.
Everyone has to do what they are comfortable with.
I'm just going by the dozens and dozens of installs into 8" chimneys
that our local Harman shop that we deal with has done.
And how I have done two. Including my own.
With no draft issues, of any kind, and no problems, and no "fires"...
But you are right. Do what you are comfortable with. I will never argue that point.
But there are many that agree, that a lot of installation/operational issues,
provided by any manufacturer of any product, often times write them very conservatively.
Dan