Understanding the air space in front glass

Hello all, getting ready for my second full season burning coal in my Harman Mk III. I have an air space on the glass, I think on both the top and bottom horizontals. When I burn wood I get smoke in the house and burn wood only to start the coal. I know coal likes air over top (but not a good technical understanding of why). If I burn wood for a one day heating, can I seal off this air space? Also had a chimney fire last year (squirrel nest) and couldn't control the air suction through that air space. This forum is fantastic, I wouldn't have made the jump from an old wood stove to a Harman without this forum and your helpful advice. I may try to come to the Meet n Greet in October.

Without a chimney fire or squirrels nest burning wood should work fine with glass air.

You will always get smoke leak starting a new fire in a cold chimney till chimney warms up a bit.

If smoke leak is highly objectional then build a smaller very hot wood fire to quickly warm chimney, or even a nice long blast with a heat gun or a hair dryer can get chimney warmed before starting the wood.

What Mac said.

When the house is warmer than the chimney, the house wants to become the chimney. When I had slow to warm up stoves or fireplace, I'd get my kindling ready and then first place a large, crumpled-up ball of news paper in, or as near the opening to the chimney as possible. Several sheets of news paper will make a good volume of heat.

I'd light the paper and quickly close up the stove, except for partially opening the ash door damper. Then, let the paper burn to pre-heat the chimney. When the paper burned out, I'd then go back in and light the kindling. Some stove and chimney systems need that two-step starting process to get a draft going.

No smoke from back draft or leakage from a sluggish draft.

One of the best parts about coal is you don't have to restart the stove alot.

Paul

Shikellamy wrote: ↑

Wed. Aug. 28, 2019 7:13 pm

I know coal likes air over top (but not a good technical understanding of why).

It has been a long time since I used hand-fired equipment, but AFAIK wood and bit coal need overfire air to support proper combustion of volatiles, while anthracite generally does not (other than during reload). And while some may see merit in air-washing the glass, as an advocate of efficiency I am horrified by the way it squanders perfectly useful anthracite btu's up the chimney. As Jeff Foxworthy already may have noted, if you would rather look at a fire than make the best use of the heat it produces, "you might be a pyromaniac". Just sayin'...

Mike

True indeed!

But, some do value their cleaner glass over getting the top efficiency...what is the usefulness of having glass to be able to view and show off the flames in the first place and that glass would always quickly becoming dirty, hence the air wash.

The alternative is a piece of heavy gauge metal in place of the glass with full gasket around it.

Stove shoppers in stove show rooms might be more apt to plunk their money down and choose the pretty one.

Another alternative is to let the glass frost, which (with minimal periodic cleaning) still provides the glow of the fire without sacrificing btu's.

Mike

McGiever wrote: ↑

Wed. Aug. 28, 2019 11:01 pm

... or even a nice long blast with a heat gun or a hair dryer can get chimney warmed before starting the wood.

Do the above with damper closed & door cracked...
Have some kindling and paper in there ready to light...
Let the stove get warm several minutes...
After stove is warmed to touch from dryer, heat gun, propane torch...
Light paper, leave door cracked, when paper catches good then open damper, this will cause a blast of warmed air to go up chimney while cool oxygen rushes through cracked door to fuel the fire. Pre-heated stove air has no place to go but up.

You’ll get much more warm air up the chimney by initially trying to hold SOME heat in the stove. Key is closing damper and other air controls and allowing time for stove to warm thoroughly.

I’ve had my best luck from cold starts with this technique. Others may have a different experience.

When house is warmer than chimney, then leaving stove door open for 10-15 minutes can aid in lighting the stove on a cold start.

I’ve always found hardest starts to be when house and outside temps are nearly identical, or house is colder than rising outside temps, or damp evenings.

Thank you. All great comments. Interesting about the house being warmer than chimney. The stove is in a winterized cabin and when I start it up the inside may be 35 while the chimney above roof is iced up. But I will try it all. I wonder why people say you cant burn both in a stove? Wood fire seems to get hot real quick but coal is ~200. Thanks again!

You can burn both, but not for long, and only with very little amounts of wood. The wood burns faster and it's fluffier ash tends to clog up the spaces that the coal needs to be able to keep burning well. Been there, found out the hard way.

Paul

I have a Mark II which is similar to your M III and all of the advise given above about the best way to start a fire from a cold start is what I do. As far as there being no gasket in either the top or bottom of the window glass for the air wash I also found a fair amount of heat loss with this overfire air. I do like to keep the glass as clean as possible ( although after a couple of years it will pit and fog up anyway) I put a gasket on the horizontal top part of the glass and left the bottom open for the wash. It did help a lot with retaining heat in the stove yet also helped keeping the glass cleaner for a longer period of time.

I also burn wood in it during the shoulder months (only because I still have some left from my wood burning days) and it is just good enough to take the cold out of the house but it needs to be tended often and will be out in the morning.

Thank you, I do remember wood ash causing problems last year, and I will look at options for gasket material. Thank you.