Harman Magnum Stoker Timer Settings/Setup

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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Posts: 204
Joined: Sat. Oct. 25, 2008 9:02 pm
Stove/Furnace Make: Harman Magnum Stoker

Post Mon. Jul. 20, 2009 4:46 pm

Horace wrote:Do it, you'll love it.
4. It is slightly quieter. Unfortunately, it's the distribution blower that's the noisy one (at least on my stove). I have not modified the distribution blower; it runs from the timer at full speed (and temperature, and noise :x )

5. Not the distribution/convection blower but the combustion blower runs cooler. Much cooler. Distribution/convection blower is still noisy and hot.

For $21 at Lowe's it's a worthwhile project. I figure that I made that back by burning up the coal that would normally have gone unburned. If you have any questions or would like to see pictures, let me know.

Love to see the pics!!!

As far as the distribution blower noise... My stove will be in the family room. But my distribution blower will be in the basement with the return air ducted in from the living room to the blower which is in opposite side of the house (My home is a center hall colonial with the Living Room on 1 side and the Family Room on the other). The blower output will be ducted to the stove. This performs 2 functions.

  1. eliminates the distribution blower from the Family Room so less noise.
  2. circulates the warm air through the 1st floor so the whole house will stay warm.

I guess this would also have the third benefit of running the distribution blower cooler. I think it'll be a worthwhile project but probably a lot more than $21. The hardest part is to cut the floor/wall where it's the most "Wife Acceptable".

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Joined: Thu. Sep. 18, 2008 12:15 pm
Hot Air Coal Stoker Stove: Harman ST8-VF8 / Frankenstove
Location: Central PA

Post Fri. Sep. 04, 2009 8:45 am


Attached is a shot of my set up for power to my Magnum. Working from left to right:

A switch that kills the whole system. This is not required, but it's nice to have the ability to flip the switch when emptying the ashes so that the dist. blower doesn't blow fly-ash out of the pan.

The receptacle is split; the top plug is NOT controlled by the rheostat - the Harman control box is plugged in there. The bottom plug is controlled by the rheostat - the combustion blower is plugged in there so I can regulate the airflow to the coal.

The dist. blower and feed motor are plugged into the Harman timer box as normal.

The rusty-looking crap on the covers is exactly that. When I shut down the stove last year, I moved this and, not thinking of it, put it on the floor beneath the flue opening. One good rain and .... grrr. We learn as we go.

I had hoped to run some ductwork this summer to also pull air from the cold parts of the house. Unfortunately, I did not get that project off the ground. Just too nice to work inside. I do run the dist. air upstairs (stove is in the basement) and this made an incredible difference in the heating of my house: It's Ugly, But It Works

Good luck with your project. Now that the weather has gotten a little chilly, football has started, and the kids are back in school, I'm back on the forum more often. If I can offer any help, please let me know.
The best weapon and tool one can ever possess is patience.

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Hybrid Guy
Posts: 25
Joined: Sat. Aug. 02, 2008 11:08 am
Stove/Furnace Make: Harman
Stove/Furnace Model: Magnum Stoker
Location: Far Northern, PA (on the border)

Post Sun. Sep. 26, 2010 9:32 am

I like the idea of running the combustion blower all the time, at a slower speed. I think I'll try that myself this year.

I found this topic thread because I was not pleased with my Harman Magnum's performance this past fall and spring. The fire kept going out whenever the outside temps got up to 30ish. But, I did make alot of changes to the house last summer (more insulation, all new windows) and I set the distribution blower to stay on all the time. After reading some of these posts, maybe having the distribution blower run constantly wasn't the best thing to do.

What I don't understand, and I'm hoping somebody can educate me, is the Magnum supposed to cycle on periodically just to keep the fire going? It seems to me that if my thermostat isn't calling for heat, the timers will never come on and feed coal?

I had to resort to leaving a window cracked open most of the winter, and that seems like a waste!

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Hand Fed Coal Stove: DS Machine 96K btu Circulator
Coal Size/Type: Nut
Location: Denver, PA

Post Sun. Sep. 26, 2010 8:16 pm

Yes the timers are supposed to come on to keep the stove in an idle mode. I believe you have an off time, on time, and distribution time.
Off time= time that coal is not being fed.
On time= time that coal is to be fed
distribution time= amount of time distribution fan is on after coal stops being fed.

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Hybrid Guy
Posts: 25
Joined: Sat. Aug. 02, 2008 11:08 am
Stove/Furnace Make: Harman
Stove/Furnace Model: Magnum Stoker
Location: Far Northern, PA (on the border)

Post Thu. Dec. 08, 2011 5:00 pm

I figured out (for me) it's best to leave the timers alone. I adjust the wing nut for the pusher block. This changes the depth of the burning coals. I can go from hot coals almost spilling over the end, to a bed of burning coals only about 1" deep. It's surprising how only 2-3 revolutions of the wing nut/lock can change how much heat output I can get.

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