Coalpail.com Forum

I've started the installation of a window on my hand fed coal furnace. I ordered a piece of ceramic glass 4 x 8 x 3/16 inches. So far I've cut a hole where the secondary air vent was (I have other means of feeding secondary air). The hole I cut is 3 x 7 inches which leaves a half inch overlap of the glass. I also gave the load door a fresh coat of stove paint.

Cutting the hole required quite an effort to get thru 3/8 inch thick cast iron with a jig saw haha.

A few questions about mounting the glass. I would really like to put the glass on the outside of the door since I can make it look better. How should I seal it? I was considering just using some high temp silicone. Would that be ok or should I use a rope gasket? I bought 4 machine bolts with nuts and washers. I was planning to drill holes at 4 points around the glass to secure it. I realize any amount of tightening might crack the glass so I'm unsure what to do there. The small holes you currently see in the pictures held the secondary air mechanism in place, I'll seal those with a nut and bolt. Any advise appreciated

Edit: rotated picture

Two to four steel strips one eighth thick over thin fiberglass wrapped around glass secured with 10x24 screws. One piece would look nicer but harder to do and the stove is in the basement.

Yep, that'll do er:)

Thanks fellas I was also thinking if I were to mount the glass on the inside, I could make a window frame on the outside out of sheet metal to cover the irregular edges of the hack job I did with the jig saw. I don't really need showroom quality cosmetics since the furnace is in the basement, but wouldn't like it to look too hillbilly either.



Does it matter if the glass is mounted on the inside or outside of the door?

franco is right... just 2 metal strips on either the top bottom OR side side (whichever you prefer) will be fine. I would use sticky back glass gasket with than graphite crap in it (last a very long time), I would definitely mount on the inside of the door and you can clean up the uneven edge with a simple 4-5 inch grinder with a Norton disk or whatever (would take 4 minutes tops)... You could even chamfer the outside edge nicely with the grinder too if your experienced with them

Cool Doug Thank you!

Your chimney job turned out nice! Good work.

You mentioned you already have secondary air covered, but for future reference if anyone does this and needs to account for secondary air.....

Just put the rope gasket on two sides of the glass instead of all four. Harman does this on their Mark III's and probably other units too. They call it air wash and it keeps the glass clear. It worked on the Mark III I have. The glass stayed clear and never got frosted like on my stokers.

Oh wow. That's nice to know. Maybe I will only seal the long sides and leave a 1/32 gap on the short sides to keep the glass clean

That would work if I mounted the glass on the outside of the door.

The gasket on my Harman was on the sides of the glass, leaving the bottom and top 'loose'. If your long side is too long for comfort to go without a gasket, you could put a small piece of gasket in the middle of the long side allowing air to flow on both sides of it.

The gap at the bottom & top was only from the gasket thickness on the sides keeping the glass away from the door.

I understand partner Thank you for the suggestion! I will definitely incorporate an air wash into my new window.

Thanks again to all members that freely lend knowledge and suggestion. I'm grateful to have such an awesome resource at my fingertips!

All done and mounted

Here's the tiny gap for the air wash. There is one on each side. I had to mount the window on the outside of the door so air would cross the inside of the glass.
Heres the inside of the door...
Finished..
Overall, I'm pleased with the turn out. Its not perfect by any means but will work just the same.. Everything looks nice with fresh paint Now I have a 3x7 inch viewing glass. Other than just being able to watch the fire, This will be a big help with setting my secondary air to get the most efficient burn

Good job and looks nice.

Very nice job. I've wanted to do that for years to my boilers load door but didn't have the cahonies to cut the hole in the door. I am feeling emboldened.

coalkirk wrote:Very nice job. I've wanted to do that for years to my boilers load door but didn't have the cahonies to cut the hole in the door. I am feeling emboldened.

Ive always thought manufactures would be wise to put a small glass view on boilers/furnaces (the cost is so minimal and it make the unit look MUCH better) great idea lightning!
time to place a Pat. Pending on furnace/boiler with glass for fire viewing then sell the rights to Dave & Matt to use the idea

Thanks fellas!! Was a little unnerving cutting a hole in a perfectly good door lol. Measure 3 times, cut and drill once cuz it's the only chance ya get No room for an extreme screw up