SS liner or pipe for fireplace install

[arcane]

I am in the proccess of installing a wood stove in frontof my fireplace.
The stove sits on the hearth. Hearth is 17.5" made up of 3 layers of brick ~ 8" above the floor.
R = 1.1 for the stove and 6" flue pipe
I've extended the hearth 2'X5'using several layers of durock and tile.
The extension is now 7.5" below the main hearth and about 3/4" above the carpet.
The fireplace is all brick 60" wide FP opening is >36x26h" 20"deep)
The house is 30 years old 2 story
External chiminy is about 22' high from hearth. 8x12" OD clay flue

A local Sweep gave me 2 options

1. install a 6" SS liner.
( I would prep the damper (ie cut for 6" SS) and I install blocker plate after he runs the liner)
~875 if I do the dirty work
2. His recomondation. Install an oval pipe and T with block off plate to reach the 1st flue tile
(this would be removable for cleaning and he a says it's okfor my 6" flue given my clay flue size)
( I'm not sure about this option for external chimney but the cost is ~475)

3. A third option is to wait till spring and by a 25' ss liner kit and do it myself w/ a block off plate

One other concern is the wood mantel. its a 3X6" wood mantel on top of the brick. It's 25" above the stove.
I may have to raise the mantel to 36" above. I can fill the space above the brick with 1 or 2 layers of durock 1/2" each
Does this need to be offset from the sheet rock to create an airspace behind or would 1 or 2 layers of durock be sufficient?
I have 2 1/2" 1'x5' strips of durock

 

[edthedawg]

Looks like no matter what, you're going to need a T if the stove sits out front - but only option #2 includes the T? I guess I don't really see the difference in the net result of #1 and #3 - you wind up w/ a full-length 6" SS liner either way. If you have to cut some steel and/or masonry to get the 6" round liner down past the smoke shelf, it's usually ok to do so.

Your 6" SS liner should run from the T to the top of the chimney (if I read #2 correctly, it would "direct vent" by terminating just above the ovaled pipe?? - don't do that) with sealed sheetmetal plates on top and bottom, to keep the heat in, and prevent room heat from escaping up thru the flue, around the liner. Assuming this is exterior wall, you should very likely insulate the liner as well.

Hearth sounds fine, presuming your "several layers" of Durock actually are like 5 or 6 layers (R for 1/2" Durock is about 0.2 to 0.26, depending on who you ask) and the stove is gonna sit up higher on the original hearth. What stove model are you installing? The Jotul #3 there?

For your mantel issue, you have to check the specific clearance requirements of the stove - can't help you there. But if you can obtain those requirements, and post some pics of the current wall, i'm sure we can help you w/ some alternatives...

 

[webbie]

Most mantels can be protected by a heat shield of sorts - and these don't look bad if done right and painted.

As to the lining - the sweep may be wrong about suggesting an option for not fully relining. Exterior masonry chimneys can only be up to twice the cross section of the pipe....without the need for lining.

So, most 8x12's are about 7x11 inside or approx 75 sq inches.
A 6" flue is about 28 sq. inches.

According to the NFPA, this would require lining. I would vote for a full reline anyway, just for ease of cleaning and draft. And, heck, if you are going to have to do the plate, cut the damper, etc. - you might as well go all the way!

 

[arcane]

options 1 and 3 would use a T as well

#3 stove

The heart is a split level. the main hearth is 7.5" above the extension
R value for the extension at 7.5" below per many sources can be reduced 60%

See attached diagram ( I did not detail the 36x26.5x 20") deep fire place. the stove would sit just out infront.
I just detailed the external 60x50" brick front and 17.5 hearth

 

[edthedawg]

I second the heat-shield idea for underneath the mantel, if you even think it's necessary. If the stove sits out beyond the plane of the mantel face, it's technically not "above" the stove. There's all manner of different thoughts on this, but I think it's safe to say that 2+ feet of clearance is pretty safe for you to start it up, see what you need, and make adjustments/additions as needed. I've got an IR thermometer and I check the underside of my mantel occasionally but - while closer than yours, and yes it does get hot - it's never in that 180ish degree danger range where I get really worried.

 

[pinewoodburner]

I am in the proccess of installing a wood stove in frontof my fireplace.
The house is 30 years old 2 story
External chiminy is about 22' high from hearth. 8x12" OD clay flue

A local Sweep gave me 2 options

1. install a 6" SS liner.
( I would prep the damper (ie cut for 6" SS) and I install blocker plate after he runs the liner)
~875 if I do the dirty work
2. His recomondation. Install an oval pipe and T with block off plate to reach the 1st flue tile
(this would be removable for cleaning and he a says it's okfor my 6" flue given my clay flue size)
( I'm not sure about this option for external chimney but the cost is ~475)

3. A third option is to wait till spring and by a 25' ss liner kit and do it myself w/ a block off plate

Couple of comments. House is 30 years old. Is the sweep certified to inspect the liner. If the liner has shifted or has lost some morter in the flue joints, you will want a full liner. You will have to send a camera down the flue to inspect this.

Your flue 8 x 12 is the max size for the stove. That will hurt your draft, but your chimney is 22 feet which will help, but it is outside so that hurts the draft. If you run a liner and insulate it, you will bring the flue up to code and have the best possible draft.

May also want to check with the insurance company to see if they have any requirements.

 

[arcane]

edthedawg
what type of engineer?

My specialty is Electromagnetics and RF circuit design went to school in storrs for my MSE back in the late 80/90's.

 

[edthedawg]

Mechanical / Materials at UConn (Storrs 93-97), working on gas turbine airfoil and rotor overhaul & repair development.