General install question - things I ran into along the way

[jmccown]

Installed the ESW stove last night. Done the through the wall install. I installed all simpson duravent double wall pipe. Question I have is about the wall thimble. The location where it is mounted is directly beside of a stud. The circular part of the thimble actually touches the 2x4. Additionally about 4" on top of where the thimble is mounted is where my residential wire goes through the studs. Will these two things be okay given that there is a double wall pipe and an additional layer from the thimble. Thanks guys. I want to feel safe whenever I fire this thing up.

 

[babalu87]

The circular part of the thimble has to contact 2X4s otherwise it wouldnt be a good structural fit, IE it would be flopping around in the hole in your wall.

 

[jmccown]

Actually it is a slip fit two piece thimble, I imagine like they all are. Inside piece slips over the outside piece as it's fitted from the outside wall. Then the surround of each piece is fastened by four screws in each corner. But I see what you mean too Babalu.

 

[Shane]

I assume your talking about pellet vent. IF that's the case the circumfrance of the thimble does not give you adequate clearance to combustible. 3" clearance to any combustible is required. the circumfrance of the wall thimble, if memory serves, only gives you 1.5" of clearance. As for the thimble flopping around that isn't going ot happen with the face plate of the thimble properly secured to the 9 5/8" framed opening you should have.

 

[jmccown]

Yes, this is a 3" pellet double wall vent I am referencing. I have threw together a paint sketch of how my install is setup for a better idea. Don't laugh at my drawing, I just threw it together in about a minute. I haven't had time to take a picture of the install yet. But here is a rough idea.

 

[sailor61]

I am not a professional but have lived through the bad experience we all fear. I understand the reasoning behind using a stud to stabilize the masonry thimble. But I can tell you that was the only piece of combustible even close to where my stove vented through the wall - I would say you don't want the thimble in contact with the studs.

What was suggested to me for the rebuild was to cut out the nearby stud, with about 8 or 10 inches clearance above and bridge it similar to a window opening, supporting it with what i guess would be called jack studs. Then install another horizontal piece the same distance below the thimble. In order to set the thimble into position it was suggested that I then fill this box with ready-mix to act as a heatsink/firestop. Suggestion came from a retired fire prevention specialist who is a friend of the family.

Have not done this and have been meaning to post about everyone's thoughts. One concern I have is if I ever need to replace the thimble it would be a major problem to get out. Thoughts?

TJ

 

[jmccown]

When you say "have lived through the bad experience we all fear." are you saying your house caught fire as a result of the thimble being beside a stud?

 

[hearthtools]

Simpson Pipe NOW has 1" clearance and having the radiation shield of the thimble at the stud will not hurt.
your wires are OK.

and Even at the OLD 3" clearance the Simpson wall thimble Reduces clearances and the hole can be 9" but the instructions show framing dem. at
7.5" for both 3 and 4 " vent
according to the instructions.
(broken link removed to http://www.duravent.com/docs/instruct/L502_aug05.pdf) page 5

 

[sailor61]

yes it burned last winter - still laboring through the rebuild process. The various inspectors haev all said "accidental and unexplained arising from the woodstove". Knowing how the place was put together I know the only combustible behind the stove was a stud. Inspectors could not pick up on it because that entire section was totally destroyed.

 

[Shane]

I stand correced Rod. It is indeed a 7.5" framing dimension with the old 3" clearance. Is the 1" clearance on the Pellet Pro?

 

[babalu87]

Sailor
You had a wood stove vented with insulated pipe through a thimble in the exterior wall and that is where the fire originated?

I would imagine the manufacturers of that pipe would test the recommended installations pretty thoroughly?
Our wall gets warm but even when the stove is ramped up to a pipe temp of 550 its nowhere near where wood should ignite.

I am very interested in your story.

 

[jmccown]

At what temp. will wood ignite? I imagine the insulation around the outside of thimble will be okay, too, right?

 

[AIRJET4U]

Ordinarily a piece of 2 X 4 construction lumber has a catch-fire temperature of 500 degree. F

 

[jmccown]

So normal operating temps for pellet stoves is what around 400*?

 

[Shane]

Remember though after years of exposure to heat a process called pyrolosis happens. The wood basically becomes super dry and can ignite at temperatures as low as 200 degrees. That's why many ZC chimneys last 10-20 years installed improperly contacting framing then all of a sudden whammo the house lights up.

 

[jmccown]

Well, seems I am getting mixed answers on this topic of the wall thimble. I think just to be on the safe side I am going to cut more holes in my wall and move it over about 3-4" away from the stud. I want to be able to sleep at night and not have to worry about that stud heating up too much.

 

[hearthtools]

I stand correced Rod. It is indeed a 7.5" framing dimension with the old 3" clearance. Is the 1" clearance on the Pellet Pro?

All the pellet vent has been tested at 1"
the PDF link I gave showed 1" for the standard pellet vent
The Pro has a differnt PDF file.