Hotblast Load Door Viewing Window

Hey folks! I decided to get brave and install a viewing window into the load door of my hotblast furnace! I got this idea after reading Lightning's post from a few years ago and thought I would share my experience as well. The window I installed is smaller compared to others that have done this modification, however I am very pleased with the end results. The glass I purchased only measures 4" x 4", and after I installed it my total viewing window is only about 3" x 3". This being said, I still feel as though it is plenty big enough. It is only for me to see how the fire is burning so that I don't have to open up the door. I found a great price on the ceramic glass as well, which is one reason I decided to tackle this modification. I only paid about $9 for the glass from mcmaster-carr.com in case anyone else wants to try and tackle a mod like this. They also have other sizes available smaller and larger. Anyway, hopefully when I fire the stove up in a couple of weeks, it will perform well and won't cause me any headaches. If anyone see's anything that they think is questionable about what I have done, please let me know! I would appreciate the feedback.

You will notice I designed the window to mount above the load door damper. Even though my load door damper stays closed all year long while burning anthracite coal, I thought it might be nice to still be able to utilize it in case I decide to burn a little wood in the shoulder months. You will also notice that I designed the glass to be able to move a little bit. The glass can not only move side to side to side, but also in and out with the use of springs. I felt like this was a good approach due to thermal expansion and also in case there are ever any puff backs. If there would be a puff back (I've only ever experienced one small one so far), my thinking was that the pressure would want to push the glass out away from the stove. The use of springs allow the glass to move away from the stove a little bit, but then they would then push the glass back against the stove once the pressure subsided. Stainless steel hardware was used to mount the glass as well. I did leave the smoke screen still attached to the inside of the stove and it does partially block my view of the rear of the stove slightly. However, if I just lower my head a tad I can see the very back with no problem.

Wow, nice job man!
you'll love it

Thanks! I just wish I could fire up the stove sooner. I mean I could, but we would be roasting more than usual lol.

Right! Fire up time is right around the corner

No gasket? Or did I miss something?

fig wrote:No gasket? Or did I miss something?

I don't know that a gasket is really necessary, but I could be wrong. I think some people used a gasket as a spacers to get a small gap on two sides of the glass in order to get the air wash affect. I didn't need to add anything to get a gap due to the thin plate that was already attached to the cast iron door. Because there is already an intentional gap on two ends, what does the gasket achieve on the other two sides? Maybe a slight cushioning affect for vibration? I also examined some fire place doors (not a stove or furnace but there is high heat) and they kind of just float in a frame without gaskets so I thought I would be ok. If its deemed necessary that I need a gasket, I could easily add one.

Ok. Interesting.

If there is a gap you will know it because you will have flames around it from it burning the coal gasses. Mine does that but a tiny bit of air wont matter. If it did Surdiacs wouldnt work at all with the small pieces they use. Your size is plenty big to view the fire. I think my Frankenstove is 2" or 2.5" round (My chubby's is smaller than that), which is a lot smaller than 3" square. (Mines a different stove but it doesnt matter with a window) You will really like it, being able to see how well the fire is burning. Good job. Dont over think it, it will work fine.

Lightnings post has a wealth of usable information for mods from several users. It almost should have a sticky on it, along with his bands videos, lol. (Maybe Lightning could put music to his post )

warminmn wrote:If there is a gap you will know it because you will have flames around it from it burning the coal gasses. Mine does that but a tiny bit of air wont matter. If it did Surdiacs wouldnt work at all with the small pieces they use. Your size is plenty big to view the fire. I think my Frankenstove is 2" or 2.5" round (My chubby's is smaller than that), which is a lot smaller than 3" square. (Mines a different stove but it doesnt matter with a window) You will really like it, being able to see how well the fire is burning. Good job. Dont over think it, it will work fine.

Lightnings post has a wealth of usable information for mods from several users. It almost should have a sticky on it, along with his bands videos, lol. (Maybe Lightning could put music to his post )

Thanks and for a total of about $15 and half of a day of work I think it will certainly be worth it too. I also agree with you regarding Lightnings posts. Without them I may not have ever burned coal, or not burned it for too long with this stove that I have. They have been really informative. This site in general has really been a blessing for new users. I'm going on my third winter now, and feel like I picked it up extremely quick from all of the reading I did before I ever even bought the stove.

That gap for air wash looks good. What is it roughly? 1/16 - 1/8 inch? That should work well and thank you for the kind words regarding the helpful posts! You'll love the viewing glass, it makes for taking cool coal pictures too.

Lightning wrote:That gap for air wash looks good. What is it roughly? 1/16 - 1/8 inch? That should work well and thank you for the kind words regarding the helpful posts! You'll love the viewing glass, it makes for taking cool coal pictures too.

The gap is approximately 1/16". I did not want anything larger than that as I don't want to much air over the fire. I'm even worried that may be to much. Typically I don't allow any air over the bed and the coal seems to burn well that way. The only air over the bed that gets in is just whatever leaks the stove may have.

Well, I have waited long enough to fire up the stove this year. Postponed my fire up about 2 weeks more than the previous two years. I have been anxious to fire up just so I could see how the new window looks and tonight was the night! So far so good. The fire looks great through the glass.

Looks good.

very nice modification!

Thanks guys.