How Can a Stoker Overfire?

A Coal stoker furnace or stove controls most operations including automatically feeding the coal. They are quite similar to any conventional oil and gas units and easily operated for extended periods of time. They commonly use rice coal but may use larger sizes like buckwheat. They can be used as primary heat, supplementary heat or have a dual set up with your existing oil/gas furnace.
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Kubota2007
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Posts: 40
Joined: Sun. Jan. 19, 2014 9:23 am
Hot Air Coal Stoker Stove: Harman Magmun 20yrs old,Harmon Super Mag just installed.
Coal Size/Type: Rice
Other Heating: Electric,
Location: Ne Pa
Contact:

Post Thu. Feb. 27, 2014 7:25 am

Reading owners manual, warranty void if Stoker is overfired, How can it happen and how do I protect it from happing? I could understand a handfired being overfired.

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oliver power
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Posts: 2266
Joined: Sun. Apr. 16, 2006 9:28 am
Stoker Coal Boiler: KEYSTOKER Kaa-2
Hand Fed Coal Stove: Hitzer 50-93 & 30-95, Vigilant (pre-Vigilant-II), D.S. 1600 Circulator
Baseburners & Antiques: MANY (Mostly when burning wood)
Location: Near Dansville, NY

Post Thu. Feb. 27, 2014 7:59 am

Good question??? However, I do know someone with a Harman Mag Stoker who says he has to run the stove hard in order to heat his place. He told me, every year he needs to replace his damaged grates.

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Flyer5
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Posts: 10382
Joined: Sun. Oct. 21, 2007 4:23 pm
Stoker Coal Boiler: Leisure Line WL110
Hot Air Coal Stoker Stove: Leisure Line Pioneer
Location: Montrose PA
Contact:

Post Thu. Feb. 27, 2014 8:07 am

In this weather our 220 furnace in the shop runs flat out almost 24hrs a day. Not sure what defines over fire. We do not make anything that can be over fired. If it is over fired coal just falls off the grate. If the ash pan is empty it may ruin it.
http://www.leisurelinestove.com


You know when people say it was "better back in my day"?

They were right.

Badog
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Posts: 111
Joined: Tue. Nov. 06, 2007 3:39 pm
Stove/Furnace Make: Alaska
Stove/Furnace Model: Liberty
Location: Lehigh Valley Pa.

Post Thu. Feb. 27, 2014 8:24 am

The rheostat on my Alaska failed and when I discovered it hot coals were being pushed of the end. It was very hot but no damage. I was smart enough to disconnect the feed motor but leave the combustion blower on. Otherwise I suspect the fan would have melted and maybe without air the grate would over heat but the fire does not stay hot or last very long once the combustion air is off.


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titleist1
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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 Thu. Feb. 27, 2014 8:28 am

Basically it would be having the combustion fan blow too much air under the grates while feeding coal so fast that burning coal is going off the end of the grates. They have a pic in the old mag stoker manual indicating what overfiring looks like but there is no description saying how to avoid it.

Besides overfiring, too much combustion air could also pressurize the firebox causing CO to leak into the living space. That is why when setting up the restrictor plate on the combustion fan of the stove a manometer reading in the firebox as well as the flue pipe should be taken.

I am very surprised at the yearly grate replacement. Mine runs pretty much full time usually for about 2 months of the year (three months this year) and the grates aren't getting damaged. If he is cementing them in place maybe they are warping due to lack of movement.
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!!

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oliver power
Member
Posts: 2266
Joined: Sun. Apr. 16, 2006 9:28 am
Stoker Coal Boiler: KEYSTOKER Kaa-2
Hand Fed Coal Stove: Hitzer 50-93 & 30-95, Vigilant (pre-Vigilant-II), D.S. 1600 Circulator
Baseburners & Antiques: MANY (Mostly when burning wood)
Location: Near Dansville, NY

Post Thu. Feb. 27, 2014 2:48 pm

titleist1 wrote:Basically it would be having the combustion fan blow too much air under the grates while feeding coal so fast that burning coal is going off the end of the grates. They have a pic in the old mag stoker manual indicating what overfiring looks like but there is no description saying how to avoid it.

Besides overfiring, too much combustion air could also pressurize the firebox causing CO to leak into the living space. That is why when setting up the restrictor plate on the combustion fan of the stove a manometer reading in the firebox as well as the flue pipe should be taken.

I am very surprised at the yearly grate replacement. Mine runs pretty much full time usually for about 2 months of the year (three months this year) and the grates aren't getting damaged. If he is cementing them in place maybe they are warping due to lack of movement.
Hi titleist1, Don't know what to tell you about grates warping , All I can tell you, is what he told me. We were talking about his Harman Mag Stoker. Which is how he heats his place. I liked the concept of the vertical feed.

Pacowy
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Posts: 2732
Joined: Tue. Sep. 04, 2007 10:14 pm
Stoker Coal Boiler: H.B. Smith 350 Mills boiler/EFM 85R stoker
Coal Size/Type: Buckwheat/anthracite
Location: Dalton, MA

Post Thu. Feb. 27, 2014 3:35 pm

I think the manual defines overfiring to be any time when an external part of the stove or smoke pipe is glowing red. It can occur as a result of excess draft, and apparently as a result of running the unit with any of the doors open. I never heard of that latter one with the old Mags, but it's in the Super Mag manual.

Mike

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