Harman Mark II, overfiring damge?

Harman Mark II, overfiring damge?

PostBy: hamiltow On: Sat Feb 16, 2008 3:43 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 ?
hamiltow
 
Stove/Furnace Make: TBD
Stove/Furnace Model: TBD

Re: Harman Mark II, overfiring damge?

PostBy: coaledsweat On: Sat Feb 16, 2008 3:57 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.
coaledsweat
 
Stoker Coal Boiler: Axeman Anderson 260M
Coal Size/Type: Pea

Re: Harman Mark II, overfiring damge?

PostBy: titleist1 On: Sat Feb 16, 2008 4:02 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.
titleist1
 
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

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Re: Harman Mark II, overfiring damge?

PostBy: grizzly2 On: Sat Feb 16, 2008 4:24 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:
grizzly2
 
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.

Re: Harman Mark II, overfiring damge?

PostBy: LsFarm On: Sat Feb 16, 2008 4:27 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
LsFarm
 
Stoker Coal Boiler: Axeman Anderson 260
Hand Fed Coal Boiler: Self-built 'Big Bertha' SS Boiler
Baseburners & Antiques: Keystone 11, Art Garland

Re: Harman Mark II, overfiring damge?

PostBy: hamiltow On: Sat Feb 16, 2008 5:16 pm

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

Thanks again.
hamiltow
 
Stove/Furnace Make: TBD
Stove/Furnace Model: TBD

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