Problem with block off plate install Update: Finished

[OhioBurner©]

After hearing about how well a block off plate has worked for some people to retain heat, and the poor heat output I am getting out of my Rockland despite its reputation, well I think I need one.

I've read over the article and have a few questions still. One thing, I have lots of silicone like GE I clear, will that really be ok to use in such proximity? My plate would only be a couple inches from the stovetop, and my Rockland routinely sees 700-750 when I load it fully. Seems awfully hot for silicone but I guess I dont really know how hot silicone can take.

Another thing, the article mentions using furnace cement around the pipe. If it were cemented in place how does it 'give' for installation and removal? I didnt install the unit myself, but would the pipe not have to move up a couple inches to unhook it from the collar?

The article mentions nothing about insulation, yet many say to add insulation to the top of the plate. Is insulation helpful? Does it need to be a specific kind? I believe its double wall pipe were it will pass through the block off plate but not 100% sure until I pull it and look (tomorrow).

Lastly, the article shows a piece of angle iron but says nothing of it. Is it necessary? Can it be installed with just silicone? #4 in the photo:


I plan on letting the stove die out in the morn and taking the day to clean the chimney for the first time and inspect everything. Will pull the insert and hopefully install the block off plate. It suppose to warm up the next few days so that should give everything time to dry (meaning I wont need to burn the insert).

Thanks for any help!

 

[Jutt77]

Are you referring to #4 the steel lintel as the piece of angle iron? My fireplace was constructed with one.

I just made my block-off plate using 28 gauge steel and since I had some flex liner insulation and spray adhesive left over, I used that to insulate the block off plate. I cut the piece of insulation the same shape as my plate but just a bit larger to help seal the edges and then glued it on with the adhesive. I then cut the hole in the insulation (for the 6" liner to pass through) small enough that the insulation was snug enough against the liner to not require any further sealant.

Just got my fireplace ready for my insert which will be here on Thursday.

It aint pretty but it works:

 

[Rudyjr]

Ohioburner, I have made the one on my stove and my buddies stoves from pan material from an HVAC supply house, 2j supply in Columbus. The same material that you use to create cold air returns between studs.I make a cardboard template that fits the opening first. Very easy to form a flange around the perimeter. Then I hold it in place with a few Tapcon masonry screws and caulk around the perimeter with hi temp silicone, the red stuff again from 2j. I also have put a layer of Rockwool firestop insulation above the ones we have done to help seal around the pipe, picked that up form the nice folks at Edwards insulation in Columbus. If you look at the photos of my install you can see how I did the opening around the pipe, this allows you to move it up and down some and then you can form the serations to the outside of the pipe to seal it somewhat. I chose not to use furnace cement around the pipe because I figured it would not stay put. Any other questions feel free to shoot me a p.m I live in Central Ohio as well. Jim

 

[burleymike]

My block off plate is about 3" above the top of the air jacket, I used silicone and it has held up fine even with near 800 degree stove top temps. I don't know how hot the air jacket gets but it is not enough to cook the silicone.

I put 3" of fiberglass insulation on top of the block off plate. At around 400f the binders will burn off and it would take close to 1000 degrees to melt the fiberglass.

 

[BucksCounty]

I placed rockwool above blockoff plate. I just shoved as much as Icould up there. I am not happy with the block off plate itself. I tried the silicone for a seal but it wasn't a clean seal. This has seemed to work well. I plan to fix in the spring.

 

[tickbitty]

I like seeing the pics of ppls blockoff plates, thanks for this thread and for posting them.
I think the steel lintel is something they are referring to that is already on many fireplaces, not something for you to install. Mine has one, and it made me wonder how to attach the dang thing to it, it might be steel all the way up on mine, can't tell! I don't really want to take out my installed stove, but I guess I will need to to make a blockoff plate. I might cram some kaowool in the damper instead with a bit of metal underneath it as a stopgap measure (someone gave me the kaowool.)

 

[OhioBurner©]

Thank you all for the reply's. Yeah perhaps the lintel is already on mine I did not pay attention to the finer details of the fireplace construction prior to installing the insert...

Rudy thanks for the possible local connections, if I end up needing more items than I have or can get here I'll be sure to look those places up. I'm going to try a couple closer places to me first, since columbus is about an hour from me.

I have some sheet metal, masonry nails, and regular silicone. If I want high temp silicone and insulation I'm going to have to try to get that tomorrow, er today now, I mean later... I hate turning around from nightshift to dayshift!

 

[spencer186]

I used furnace cement to seal around the pipe and the edges of the plate to make sure it seals well. I wanted to put kaowool above it, but couldn't find any locally before I did my install. I would'nt be comfortable with silicon. At the very least I would use a high temp silicon. I wasn't comfy with that either so thats why I used the furnace cement. I don't really see a need to pull the stove, so that wasn't an issue for me.

 

[OhioBurner©]

Ok I cleaned the chimney for the first time and attempted to pull the insert. I dont think I am going to be able to put in a block off plate - at least the conventional way.

I was barely able to disconnect the flue... It took about everything I had to lift it up so the bottom of the flue liner came out of the stove's collar and set on it. Then there are these tabs that stick down about another inch and half or so. With everything I had I could not push it up to clear these tabs. After trying for quite some time I was only able to manage to lift it out fully by sliding the insert forward and to the side, and then popping the flue out to the side. I bet the flue moved a foot to the side to accomplish this. I dont see how being in a fixed position (meaning inside the hole of the block off plate) I could reinstall everything.

Only one thing I can think of... is it possible to lift up the entire flue assembly? I'm not sure how these are attached, I think its just clamped at the top? Its about 24' of double wall, do you think I could lift this, I have no idea how much that all weighs.

What do you all suggest? Is lifting the chimney to install the block off plate and stove feasible? Or should I consider just stuffing a bunch of insulation up there?

I attached a pic to show how far off center I had to move the liner to pop it out. The stove is also slid several inches to the side.

 

[Rudyjr]

Sorry, I am no help on the double wall pipe as I have never worked with it. If as you say it is clamped at the top maybe it could be loosened and pulled up abit and reclamped. If all else fails I know outhers on this board have had success with "soft" block off with just insulation packed at the bottom around the pipe.

 

[OhioBurner©]

Install done... I hope I got it correct.

After pulling the insert and examining the situation I could not see how I could install a fixed plate unless I was able to raise and lower the whole flue liner to instal/remove the stove. I guess other folks must have a lot more space between the top of thier stove and the block off plate to be able to have play in it enough to install/remove but mine is rigid. With the clock ticking on my last day off with the family out of town I went up on the roof in the dark and was able to raise the flue assembly up and place a couple 2x4's on end to hold the liner up about 4". I installed the block off plate and slid the stove back in, then went up and lowered the flue back down. Worked pretty well. I didnt use sealant since I was nervous about making it permanent (stove cement) and worried about the temp rating of silicone, so I just tacked it in place. I used a layer of roxul afb to help seal it, and around the flue connection I wrapped it around it to help further seal the slight gap around the hole. Dont know if it makes any difference but I also stuffed rockwool in the cleanout hole (it was just open).

Here is a quick pic, I might make another thread with a bunch of details and pics but I'm at work right now and this is the only pic I have on me.

 

[Rudyjr]

Ohioburner, Good job looks pretty much like the ones I have done. I have put rockwool above all of the ones I have done seems to help seal up everything. You should see a definite improvement in heat output now that you are not sending heat up into that space. Let us know how it works for you.