Harman Mark II, Overfiring Damge?

Modern and vintage hand fired coal stove are similar to a wood stove and in some cases can burn either. They need to be regulated and fed by hand usually every 12 to 24 hours depending on your usage. They require no power to operate making them ideal for rural settings with long power outages.
Post Reply
New Member
Posts: 19
Joined: Tue. Jan. 22, 2008 5:44 pm
Stove/Furnace Make: TBD
Stove/Furnace Model: TBD

Post Sat. Feb. 16, 2008 2:43 pm

The used Mark II I bought recently had a warped grate that I must replace. Does this always mean the stove was overfired, or will the grates warp from normal use over time?

Also, If it was overfired, can any hidden damage occur? I cannot fire the stove due to the incompleted chimney, but I was worried that it may be possible for too much heat to cause a crack, which could allow the firebox air to mix with the circulated fan air in the air passageway (air jacket), and get blown into the room via the circulator fan. Or the fan blowing air into the firebox.

Is this a far fetched concept? Are the Harman Mark stoves too well built for something like that to happen ?

User avatar
Site Moderator
Posts: 9822
Joined: Fri. Oct. 27, 2006 2:05 pm
Stoker Coal Boiler: Axeman Anderson 260M
Coal Size/Type: Pea
Location: Guilford, Connecticut

Post Sat. Feb. 16, 2008 2:57 pm

It may not have been overfired, it could be that he just kept shaking it down to far. A thin or no ash layer can eat a grate in a hurry. You should season the new grate with a small fire first. Wood perhaps, instead of coal to keep the initial heat down.

Those units are pretty robust, I don't think it could get much damage. The critical points would be the door seals and smoke pipe outlet. If all the flat surfaces are in fact flat, I doubt there is any damage.
Nothing is impossible for people who don't have to do it themselves.

User avatar
Posts: 4404
Joined: Wed. Nov. 14, 2007 4:06 pm
Hot Air Coal Stoker Stove: Harman Mag Stoker (old style) one in basement, one in workshop
Hand Fed Coal Stove: Harman Mark III on standby for long power outages
Coal Size/Type: Rice/Anthracite; Nut/Anthracite
Location: Cecil County, MD

Post Sat. Feb. 16, 2008 3:02 pm

Triple check the baffle at the top of the firebox for damage, warping, etc. If it was overfired or if the baffle is damaged and it was normally fired, this baffle can warp. I had a Mark III that the baffle warped on and it cracked both sides of the stove.
I drive a VW TDI, heat my home & workshop with two coal stokers and have two vintage JD diesel tractors....
The EPA just loves me!!

Visit Hitzer Stoves

User avatar
Posts: 842
Joined: Tue. Feb. 12, 2008 7:18 pm
Hand Fed Coal Stove: Hitzer 30 - 95
Coal Size/Type: pea and nut/ anthracite
Other Heating: Jotul #3 wood stove in garage. Oil backup in house. Electric backup in house.
Location: Whippleville, NY

Post Sat. Feb. 16, 2008 3:24 pm

The top baffle in my Jotul 3 warped badly over time and cracked. I made a plate steel baffle reinforded with angle iron. It has held up perfectly for the past two heating seasons. I am surprized to hear that titleist's Mark III actually cracked the plate steel sides. I thought plate steel would warp but amost never crack. Must have gotten all the carbon baked out of it over time. Cast iron I do know can crack fairly easily though. :shock:
The only redeeming value of winter is that I can have a fire in my stove.

User avatar
Posts: 7385
Joined: Sun. Nov. 20, 2005 8:02 pm
Stoker Coal Boiler: Axeman Anderson 260
Hand Fed Coal Boiler: Self-built 'Big Bertha' SS Boiler
Baseburners & Antiques: Keystone 11, Art Garland
Location: Michigan

Post Sat. Feb. 16, 2008 3:27 pm

The warped shaker grate is often cause by an over-full ash pan... If the ashes get deep enough to touch the bottom of the grate, the airflow is blocked, and the cooling effect of the airflow is lost, then the grate overheats..

Like coaledsweat said, it's unlikely that the stove was overfired, the owner might have just been a bit lazy about keeping the ashpan emptied on a regular basis.

Greg L
Burning Pea/Buckwheat through an antique stoker [semi retired SSboiler],
Running an Axeman-Anderson 260M boiler burning Pea, About 150-250#per day
Farming, Fixing, Fabricating and Flying: 'spare time' what's that?

New Member
Posts: 19
Joined: Tue. Jan. 22, 2008 5:44 pm
Stove/Furnace Make: TBD
Stove/Furnace Model: TBD

Post Sat. Feb. 16, 2008 4:16 pm

Thanks. I can't wait to start using the stove. I'm looking forward to learning coal burning.

Thanks again.

Post Reply

Return to “Hand Fired Coal Stoves & Furnaces Using Anthracite”