Harmon ST8-VF8 Coal Stove

Harmon ST8-VF8 Coal Stove

PostBy: fgdrury On: Fri Nov 09, 2012 10:07 am

I'm now the owner of a 1987 Harman ST8-VF8 stoker coal stove (otherwise known as "Frankenstove"). This stove is my worst nightmare. I can't seem to regulate the coal input or the heat output. It doesn't burn the rice coal evenly or thoroughly, leaving a lot of unburned coal in the ash pan. Also, coal seems to be getting into the mechanism area and jamming it all up. I've used manual loading coal stoves for the past 8 years that would cook us out of house and home but this auto feed doesn't seem to be cutting it. The wife doesn't really like the 51 degree temperature in the house. I could really use a owner's manual if anyone out there could send me a copy.
Stove/Furnace Make: Harmon Coal Stove
Stove/Furnace Model: ST8-VF8

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Re: Harmon ST8-VF8 Coal Stove

PostBy: McGiever On: Fri Nov 09, 2012 8:36 pm

Look for the Harman Magnum manual, it's what replaced that older model.

And make sure the fines are cleaned out from under the grates and that grates are fitting tight...might want to seal them (or it) w/ furnace cement. :)

Do you have the one piece grate?

You can *Search* that model number in the archives here for some good reads. ;)
Stoker Coal Boiler: AXEMAN-ANDERSON 130 "1959"
Coal Size/Type: PEA / ANTHRACITE
Other Heating: Ground Source Heat Pump
Stove/Furnace Make: Hydro Heat /Mega Tek

Re: Harmon ST8-VF8 Coal Stove

PostBy: Horace On: Fri Nov 09, 2012 10:59 pm

Congrats (although you might not think so now) on your new (old) stove!

Check you PM. The manual is pretty ... ah ... brief on details on running it. McGiever is right on with his suggestions, let me see if I can help, too.

Do you have the crack right down the middle of the grates? Mine does. Always has. It's burned for the ten years that I've owned it just fine.

The VF8 does not have an air restrictor on the combustion blower so it runs flat out and pushes more air than the stove needs. You can make one out of a flat peice of metal or cardboard and attach it to the intake of the blower with one of the screws that holds on the metal screen. When I had a restrictor I closed it by about 90%. You want to restrict the air that's going under the coal quite a bit. This should be determined by a manometer. Once it's restricted, plug the combustion blower into an outlet and let it run 24/7. Your burns will vastly improve. When you burned a handfed you never turned off the air completely, right? Same thing. Unplug it from the control box and plug it into a wall.

The Magnums have a gauge on the side somewhere that tells the operator how many dots they are pushing; effectively, how far back and forth the pusher assembly travels. We didn't get one of those. I measure mine with a ruler and the rod travels between 1/4" and 3/8". I change it depending on how wet the coal is. Your mileage will vary depending on how wet and what size (I know it's rice, but it could be different that mine) the coal is. You want to adjust this (small adjustments) so that when the stove is running flat-out the coal is burning up by the time it gets to within an inch or two of the end of the grate.

Are you using a thermostat?

The timers work like this: The ON timer (far left) sets how long at the beginning of the cycle the feed motor will run. The OFF timer (middle) controls how long the total cycle lasts. The EXTEND timer (right) sets how long the distribution blower will run ofter the ON timer has expired (I think, I usually run mine 24/7).

I have my timers set as follows: When it's fairly warm (but cold enough for heat) at 1 ON, 12 OFF, and the distribution blower for whatever is comfortable.
A bit colder and I'll bring down the off timer (the one in the middle) so it runs more often. Even colder and I'll go to 2 and 15 and run the dist blower all the time. When it's COLD i'll come down to 2 and 8. I try to keep a bigger fire this way so the stove is making more heat when the thermostat is not calling for heat. The recover times are shorter and the overruns on the T-stat are smaller. And the house is much warmer all around.

Inside the stove, to the left side, coming out from the bottom of the grate, there is a handle with a hole in it. If you pull that towards the front of the stove, you can clean out the crud that accumulates under the grates. There are two holes under there that you can root around in. Probably want to shut down to do that, or at least stop the blowers.

As far as the grinding goes, there are a couple possibilities. There's a little pan under the stoker unit - sort of opposite of the timer/control box- that catches fines. Make sure that that is empty. Also, if you can pull the hopper off when it's empty you might find some (a lot) of stray coal that worked it's way into and around the stoker mechanism. Getting that out might stop it. When the hopper is off, there are two little oil cups with flip-up lids that might need filling.

The inside top of our stoves are flat. The Magnums are slanted. The flyash in our stoves will accumulate under the stovepipe collar. It will accumulate to the point where the stove is choked off and starts to push CO into your house. You MUST clean this out a COUPLE of times per season. No one told me this when I moved into my house, and I didn't know that this site existed. Spent 24 hours in the hospital sucking oxygen. Please learn from my stupidity.

Hope all this hepls and I'm not telling you anything that you didn't already know. If you have any questions, please ask.
Hot Air Coal Stoker Stove: Harman ST8-VF8 / Frankenstove

Re: Harmon ST8-VF8 Coal Stove

PostBy: LsFarm On: Sat Nov 10, 2012 11:29 am

I have to say that is a very well written, thorough post about running the early Harman stoker.
With reading your post, who would need a manual, except for a few photos the manual might

One thing to emphasize.. buy and use at least two CO detectors. one in the room the stove
resides in, and one near your bedroom doors. The type of detector that shows a digital
readout of percentage of CO detected are the best.

A few photos to go with both the original post and the instructions would be helpful..

Gotta love this forum..

Greg L
Stoker Coal Boiler: Axeman Anderson 260
Hand Fed Coal Boiler: Self-built 'Big Bertha' SS Boiler
Baseburners & Antiques: Keystone 11, Art Garland

Re: Harmon ST8-VF8 Coal Stove

PostBy: Horace On: Sat Nov 10, 2012 12:52 pm


Thanks for the compliment. Whenever I see on here that someone bought a stove like mine I feel like I'm in a huge crowd of strangers and I see someone I know. Not many of them still around, but now that I know how to run mine - in no small part thanks to this forum - I really like it. Nothing like coal heat.

I forgot to mention the CO detectors, and you're right on the nose. After my CO adventure, I have them all over the place.

Pictures definitely would help, but I am unfortunately in the process of reinstalling everything on my PC after a fatal crash. When I get things back to some semblence of normalcy I'll try to grab a few.
Hot Air Coal Stoker Stove: Harman ST8-VF8 / Frankenstove

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