Harman Mark II, overfiring damge?

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 ?

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.

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.

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.

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

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

Thanks again.