Why does the glass reflect the heat back into the insert???

[jimmol]

Does anyone know why the WinterWarm small has reflective glass in the insert?

Good Day to All,

As I was about to add a piece or two of wood yesterday to a 4 inch bed of coals, I found myself being driven back by the intensity of the radiant heat. So I left the door wide open for a bit and during that time the temp in the room and in the course of 20 minutes the temperature in the room rose from 69 to 74 degrees.
So I have to wonder, why don't they let all that heat out as we burn? Does anyone know why it has to be redirected into the insert?

Thanks for your input

My WinterWarm small is still serving me well, though I long for the day my small 1.8 cu. ft. box grows larger.

 

[TooManyHobbies]

Maybe for efficiency and clean burning. Maybe it has something to do with the secondary burn? I know for my stove, people say the secondary burn only takes place when the temperature inside the stove is very high.

 

[jimmol]

Maybe for efficiency and clean burning. Maybe it has something to do with the secondary burn? I know for my stove, people say the secondary burn only takes place when the temperature inside the stove is very high.

Thanks for the idea.

The WinterWarm uses a Cat for secondary burn but maybe it helps it get up to temp to ignite the cat.

 

[Tech Guru]

Was an EPA clean burning thing. The IR coated glass kept the internal temperatures up and allowed for better secondary combustion and therefore lower emissions. Makes the glass more expensive to replace, and I'm not sure you'd notice that much of a difference in real world operation if you ended up using standard ceramic glass when replacement is required (as I imagine many do without even realizing)

 

[fire_man]

Possibly to help reduce front hearth clearance requirements on some stoves.

 

[Corey]

Zombie thread from last year! - buy yep, they are trying to reflect more heat into the firebox for more complete combustion. The benefit is the more 'smoke' you burn in the firebox, the more heat you can extract. It may seem like a bit of a waste reflecting that heat back into the firebox, but it should be coming out once those hot gasses hit the top sheet of the stove. ie- more heat from more complete combustion means you can damper down a bit more, burn a bit less wood and extract a bit more heat from the slow moving flue gasses.

We had a lively discussion a few years ago about detecting which side of the glass had the aluminum ir coating...turns out a multi-meter set to read ohms was able to detect the conductive aluminum vs plain ceramic side.

 

[EatenByLimestone]

Does it matter which side faces the fire?

 

[begreen]

Possibly to help reduce front hearth clearance requirements on some stoves.

Negative. That distance is established by code. The IR coating is to keep combustion temps hotter and for a cleaner glass.

 

[Corey]

Does it matter which side faces the fire?

Yes, the IR coating should be on the outside of the stove as shown above. It would likely be burned away, or scrubbed away in short order if it were on the 'fire' side of the glass. Plus, being on the outside helps keep the glass hotter for the soot removal properties mentioned above. If the coating were on the inside, it might keep the firebox hotter, but the glass would actually be a bit cooler because some IR would be reflected before ever reaching / warming the glass.

 

[fire_man]

Negative. That distance is established by code. The IR coating is to keep combustion temps hotter and for a cleaner glass.

View attachment 159828

Stove makers get their stoves tested to UL 1482 by certified labs and use the results to set specific clearance requirements for each model stove. Doesn't it stand to reason using IR glass may help them with the testing to reduce clearance?

Woodstock added an ashlip to reduce hearth clearance requirements and I was lucky enough to get the first prototype lip. My inputs regarding hearth clearance concerns actually led to the development of the ashlip. The lab monitors temperature at various points around the stove using very specific conditions (flue size/wood weight, draft settings, etc). These results are used to set clearance requirements.

"Code" certainly impacts clearance, but stoves are still tested and approved with model specific requirements.

 

[begreen]

Can you site an example? I have only seen 16" and 18" (CA) glass to front of hearth measurements in current manuals for stoves that have front opening doors. I thought that was established for when the door is opened, not closed. It is the requirement even if the stove only needs ember protection only. The Progress does not have an opening front door. Not sure if they use IR glass or not. Maybe yes? If so I think it is for keeping the glass cleaner and the combustion hotter. The ashlip and leg height are what affect the hearth extension requirement here. It's the ashlip that is acting as a heatshield. With shorter legs the h.r. jumps up to 16".

 

[fire_man]

The Progress does use IR glass. I think you area right about the minimum front clearance for doors being 16" or 18" Canada due to concern with ember roll out. But if no doors are involved, stovemakers can get "creative" to reduce clearance.

I'll see if I can find some backup info on WS site about reducing clearance due to the IR glass.

 

[ccmac]

Another thing that might contribute to the temperature elevation in your room may be that the additional air your hot coals received as the door was left open increased the firebox temps. Just something to consider.

 

[fire_man]

Begreen:

Looks Like I was correct. I just got this Email from Woodstock:

The short answer to your question is yes, the IR coating helps to reduce the hearth requirement in front of the stove. I can't remember what the numbers were without it, but using one coated and one uncoated glass on the Progress reduces the clearance, particularly with the short leg option. The numbers are still not small but better than using 2 uncoated pieces.

 

[begreen]

Thanks for the update.