Block-off plate location

[Ashful]

Below is my working plan for my block-off plate and shielding installation, for installing a Jotul Firelight 12 in a large fireplace. The drawing is a side view cross-section. Anything brown is wood. The heavy wood lintel will have a heat shield intalled, as will the wood door jambs on the fireplace opening. There is also a wood timber shown running front to back on each side above the lintel, but they exceed the 36" clearance requirement, and therefore do not require shielding.

My thinking was to install the block-off plate at an 8'-0" height from the floor, such that air can be circulated thru the old unused thimble. I came up with this after noticing how warm the smoke chamber area of my other (similar) fireplace got with the wood stove installed and running. Seems lots of warm air gets trapped / stalled in this area, and I have an opportunity here to create some nice natural or forced convection.




Does this seem like a good plan? Foolish? Dangerous? I can't see how, but it's always good to ask. Another thought was to install the block-off plate directly at or under the lintel, closing off the entire upper fireplace area from the stove. I could not figure out how to safely do this, as I suspect the plate (and the wood directly above) would get very hot, and I don't think I want to circulate air from above the block-off plate with my living space.

Before anyone who hasn't been around this summer jumps on it, the wood flooring running right up to the firebox is being replaced with a stone hearth extension.

Photos of this fireplace, as well as a similar install in another part of the house, can be seen in another old thread:

https://www.hearth.com/talk/threads/old-fireplace.88498/

Thanks!

 

[begreen]

Maybe consider skipping the lintel shield and do the blockoff right below the lintel. It would still need to be stood off from the lintel by an inch. I would also slope it slightly downward toward the back of the fireplace.

 

[Ashful]

That was the other option I was considering, but decided the above drawing was the safer and easier way to go. My concern with the block-off plate below the lintel is providing air flow thru the 1" gap at the mantel, as well as my ability to see and inspect the various wood components above the lintel. Do you favor doing the block-off plate lower for some reason, or were you just suggesting another possible option?

 

[begreen]

Seems logical. The lower blockoff plate thought was to maximize heat transfer into the room, with how much will vent out of the upper thimble being unknown. But it could be fan assisted if need be.

 

[Ashful]

Yeah, that's what I figured. I've already got 110vac running into the fireplace from the old gas insert, so no problem to wire up and install a duct fan in that unused thimble, if need be.


Sent from my iPhone using Tapatalk

 

[NextEndeavor]

Is your liner insulated?

 

[Ashful]

Yep. Blanket insulated smooth wall flex liner down to block-off plate, then single wall stovepipe from there to the stove.

One other thing I forgot to mention is all the cool stuff going on inside that fireplace. Wood lockers, beams, stonework... would be a shame to hide it all above a block-off plate!

 

[begreen]

Sounds like you have a plan. Go for it. Times a wasting. It'll be heating season real soon.

 

[Ashful]

You are right! Took the spousal unit to pick out stone for the hearth and extension this morning. Gotta run the final choice by a mason or two, as there's some questions about transitioning from the hearth to the extension.

Liner install is (finally!) scheduled for Oct.4 & 5. Those who have been following my wooden chimney woes know why it's taken so long, and why they're scheduling two days for the install. (Actually, part of the latter is because I'm also having an insulated 6" pipe slid inside the 8" clay tile liner on the other Jotul Firelight.)