Air over fire on Mark II to prevent coal gas poof.

Air over fire on Mark II to prevent coal gas poof.

PostBy: pine grove coal user On: Wed Jul 25, 2012 9:00 pm

I have a Harman Mark II. It has one air vent in the ash door.
In late Spring and early Fall I need to work hard to prevent "poof" of the coal gas when it finally lights off after feeding it. I've read all the posts I could find on how best to prevent this and have gotten pretty good at it.
My concern is when I'm not in town and my wife and kids are tending the fire. I'm looking for a more idiot proof method to prevent the rapid combustion of the coal gasses.
What I am considering is drilling two 1/2" holes in the sides of the stove, just above the fire bricks to allow a continuous flow of fresh air over top of the coals. I'm thinking this would prevent the buildup of the gas and what gas would build up with light off faster and with less force.
I have a 30' masonry chimney and my barometric damper runs at .06. I don't think two half inch holes would be detrimental to pulling the air up from the bottom.
With 1/2" holes, if it doesn't work, I could easily close them with two bolts. (My stove is old, and I have had to make multiple repairs, modifications, and customizations so I'm not worried about the aesthetics of the unit).
Does anyone think this plan is a good or bad idea?
Has anyone ever tried this before?
Do you think it will work?

( know, I should trade this unit in for a SF260 or an EFM520 but I have not yet found a good deal. )
pine grove coal user
 
Hand Fed Coal Boiler: H. S. Tarm, model 202, 1983
Hand Fed Coal Stove: Reading 'bucket a day' stove in storage, waiting for attention
Coal Size/Type: Oiled Pea coal
Other Heating: New Yorker oil burner which almost never runs, thanks to the Tarm!

Re: Air over fire on Mark II to prevent coal gas poof.

PostBy: wsherrick On: Wed Jul 25, 2012 9:10 pm

This has been tried before and was once a standard feature of most all coal stoves. All coal stoves made at the Turn Of The Century have provision for secondary air in some manner or other. Your fire needs a little secondary air to aid in combustion efficiency across the entire combustion cycle. The holes need to be exactly at the top of the coal bed so the air can mix with the combustible gas as it it generated out of the coal. Putting the openings too high will do nothing but cool off the combustion area and reduce efficiency. The top of the fire bed is hot enough that a small amount of air can be heated to the point that it aids rather than hinders combustion.
wsherrick
 
Hand Fed Coal Stove: Glenwood Base Heater, Crawford Base Heater
Baseburners & Antiques: Crawford Base Heater, Glenwood, Stanley Argand
Coal Size/Type: Chestnut, Stove Size

Re: Air over fire on Mark II to prevent coal gas poof.

PostBy: pine grove coal user On: Wed Jul 25, 2012 9:23 pm

Hmmmm, the problem then for me is the vertical fire bricks in the Harman Mark II. If I drill the holes directly above them, the holes will still be about 2" above the fire. Maybe I could install a deflector inside the fire box to direct the air down towards the fire. I wonder if this would be sufficient.

I previously considered bringing the air in through the glass frame. The Harman glass has their 'air wash' system where air comes in under the glass frame and washes up the glass (to keep the ash from settling on the glass). I was considering making these 1/16" wide slots more like 1/8" figuring maybe I could achieve the same thing from the front. But using your explanation, this will not work either because the air never gets close to the coal bed.
pine grove coal user
 
Hand Fed Coal Boiler: H. S. Tarm, model 202, 1983
Hand Fed Coal Stove: Reading 'bucket a day' stove in storage, waiting for attention
Coal Size/Type: Oiled Pea coal
Other Heating: New Yorker oil burner which almost never runs, thanks to the Tarm!

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Re: Air over fire on Mark II to prevent coal gas poof.

PostBy: carlherrnstein On: Wed Jul 25, 2012 9:59 pm

Maybe you could remove the gasket or part of the gasket between the glass and door.
carlherrnstein
 
Hot Air Coal Stoker Stove: combustioneer model 77B
Coal Size/Type: pea stoker/Ohio bituminous

Re: Air over fire on Mark II to prevent coal gas poof.

PostBy: franco b On: Thu Jul 26, 2012 10:17 am

The simplest way is to feed the fire with small batches more frequently than normal. Smaller loads generate less gas and cool the existing fire less, so light off quicker and easier. The problem is not just lack of air over the fire, but also lack of heat to ignite the gas.

Lots of air over the fire probably will not burn the gas but will flush it up the chimney so it does not puff.

Ask your wife to just put a small scoop on the fire every few hours, or load in two smaller batches rather than one big one with twenty minutes or so between. Open feed door slowly.
franco b
 
Hand Fed Coal Stove: V ermont Castings 2310, Franco Belge 262
Baseburners & Antiques: Glenwood Modern Oak 114
Coal Size/Type: nut and pea

Re: Air over fire on Mark II to prevent coal gas poof.

PostBy: nortcan On: Thu Jul 26, 2012 10:39 am

Just like William said, the holes must be located at the right place. I drilled 2 X 1/2" holes in the front doors of my Vig ll and didn't get the best results about over the fire gases burning. The holes are located too low on the doors, but at least they prevent ash dust to etch the glasses and the glassses stay clean all the season.
Maybe you could keep on you idea about the holes but drill in the stove first then take a masonery 1/2" hole saw to cut the holes in the fire brick. Easy to cut, a brother inlaw made it on his Quadrafire wood stove. These stoves have holes in fire bricks to get more air when starting a new fire.
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nortcan
 
Stove/Furnace Make: Stuart,Peterson/ Grander
Stove/Furnace Model: Sunnyside/ Golden Bride

Re: Air over fire on Mark II to prevent coal gas poof.

PostBy: pine grove coal user On: Thu Jan 31, 2013 10:24 pm

As an update to this, I think I have solved the problem!
I drilled two 3/8" holes, one in each side, just in front of the side fire bricks. In this 3/8" holes I inserted a piece of 3/8" stainless steel tubing which I bent down so it is within 1/2" of the coal. This allow air to continuously blow on the top of the coal bed. This allow oxygen to ignite the gas at the front corners of the bed, which quickly lights the remainder of the gas coming up through the fresh load of coal.
This has stopped 99.9% of the coal gas poof. I am very happy with the results.
pine grove coal user
 
Hand Fed Coal Boiler: H. S. Tarm, model 202, 1983
Hand Fed Coal Stove: Reading 'bucket a day' stove in storage, waiting for attention
Coal Size/Type: Oiled Pea coal
Other Heating: New Yorker oil burner which almost never runs, thanks to the Tarm!

Re: Air over fire on Mark II to prevent coal gas poof.

PostBy: nortcan On: Thu Jan 31, 2013 10:29 pm

Hi pgcu, looks like a good :idea: you got for the over the fire air vents. Seem to work very well.
If possible for you I would like to see some photos showing these vents.
Thanks
nortcan
 
Stove/Furnace Make: Stuart,Peterson/ Grander
Stove/Furnace Model: Sunnyside/ Golden Bride

Visit Hitzer Stoves