Quadrafire 3100 install clearances

[HighHeat22]

New install on a Quadrafire 3100 Millennium and have questions on stove clearances. Spec sheet says 17" to 6" single wall pipe and 8.5" on stove corners on a corner install. I'm going to go with 18" to stove pipe thats standard. I put up walls 1" away from drywall with 1/2" cement board and porcelain tile. I have several questions. Is the 18" clearance to the back drywall or the non-combustible walls I put up and is the corner clearance of 8.5"to the drywall or the non-combustible walls. I forgot to mention I have a 1.5" gap at the bottom of the walls and the same cement board and porcelain tile on the floor. Also have back and bottom shields on the stove. Install is a thru the ceiling and then thru the roof. I can't get a straight pipe thru the rafters the stove sits below in the middle of the rafters so I'm going to use an elbow to go thru the ceiling 4 inches over. I hate this and would really prefer a straight shot thru the ceiling and roof. My last stove I had to move the pipe 4" over thru the ceiling/roof and I never had a great draft and it was always a pain to clean the pipe. Any one else have this problem. I appreciate any help on this.

 

[bholler]

Clearance is to combustible material so the drywall.

You could always move the framing we do it pretty often

 

[begreen]

An offset when done with 45º elbows, does not present a huge restriction, Using 90s to create the offset would be worse. We have a 45s offset and our system drafts well. How tall is the flue system in total from stovetop to chimney cap?

Is there a reason that double-wall stovepipe is not being used. That too will help improve draft and is a higher quality pipe.

 

[HighHeat22]

Yes using 45 elbows. About 15ft chimney. My last chimney that I used 45 elbows on was about e30ft and yes it did reduce the draft. So on this one I should be fine. I'm really looking for answers on my clearances so I can finish the install. Not sure if I can measure my clearances from the drywall or the tile I put up. Thanks for your reply.

 

[bholler]

Yes using 45 elbows. About 15ft chimney. My last chimney that I used 45 elbows on was about e30ft and yes it did reduce the draft. So on this one I should be fine. I'm really looking for answers on my clearances so I can finish the install. Not sure if I can measure my clearances from the drywall or the tile I put up. Thanks for your reply.

As I said before the clearances are to combustibles. The nearest combustible would be the drywall

 

[ti67]

I have a Quadra Discovery III installed
(broken link removed)


It's been working wonderfully. But I'd like to put up cement board to close in the masonry stack and the air duct stack you see in this picture.

I have 1/2" Cement board I'm putting up behind the stove.

I know the clearance is good from back of stove to wall.
My question is ...when I'm cutting the box out of the cement board panels for clearance around the DOUBLE walled stove pipe, how many inches of clearance are required to be safe?
The cut outs I have currently on this panel pictured and the one that goes above it will yield a minimum of 1 inch clearance at the closest and close to 3 inches at the corners.

I'm new to this obviously, and tried to find my answer by searching this forum, but am still unclear as to proper clearance.

 

[begreen]

Cement board has 0 clearance need as long as it is cement board with no combustibles in it to lighten it up. Some use pumice which is fine, but some use Styrofoam which is not ok.

 

[ti67]

Cement board has 0 clearance need as long as it is cement board with no combustibles in it to lighten it up. Some use pumice which is fine, but some use Styrofoam which is not ok.

Thank you for your reply.
I'm using the cement boards that were here when I bought the place. They appear to be Hardiebacker wet area cement board with superior moisture and mold protection.
A web search indicates it's 90% Portland cement and sand.

"90% Portland cement and sand, plus proprietary ingredients. No fillers or abrasive aggregates."

No idea if there's any styrofoam in the remaining 10%

On their FAQ section it says
(broken link removed to https://www.jameshardie.com/product-support/resource-center/technical-documents/fire-prevention-faq?loc=refresh)

Can James Hardie products be used around a masonry fireplace?
Yes, HardieBacker® 1/4" Cement Board is deemed noncombustible when tested to ASTM E 136 and can be used in conjunction with other noncombustible materials around a fireplace. This does not mean that clearances to combustible building materials can be reduced by using HardieBacker 1/4". Clearances to combustible building materials shall be obeyed even if they are protected by noncombustible materials, please refer to your local building and fire code for specific combustible clearance details around masonry fireplaces.

As you might be able to see, on the left side of the first image I posted, I notched a stud out to comply with the clearance required for combustibles.

I'm just unsure how the Hardieboard may transfer heat to the studs though, and if that's a problem.

 

[begreen]

Hardiboard uses cellulose as a filler last I checked. Don't worry about the heat transfer to the studs. As long as the stove clearance to the studs is good, it's ok.

 

[ti67]

Hardiboard uses cellulose as a filler last I checked. Don't worry about the heat transfer to the studs. As long as the stove clearance to the studs is good, it's ok.

Ok, thank you.
So if cellulose is a filler, am I within spec if my clearance between double wall stove pipe and edge of hardieboard ranges between 1 and 3+ inches?

And given HardieBacker® 1/4" Cement Board is deemed noncombustible when tested to ASTM E 136

I attached a still pic and a quick video of the panels in place.
Thank you in advance for all your help.

I'll be on the road for a couple of days.
I know the Mrs will use the stove since temps will drop in 30s. But I don't want to leave the panels up if the clearance is a hazard.