Harman ST8-VF8 Stocker Stove

has anyone come up with a fix for this unit when it won't push coal up to the burn pan

Hi, Jeepers. Welcome to the Forum!

I have one of these stoves, too, and it's a bit cantankerous. The only times that I can think of when it wouldn't push coal onto the grate were:

1. I used really wet coal. I mean sopping wet. It actually fed, but was so slow it looked like it had stopped and eventually went out. I got around this by tightening the feed screw (that dangly thing in the back that sets how far back and forth the feed block moves) as far in as it would go.

2. The feed rod (the threaded rod that the dangly thing attaches to) had worked its way out of its threads on the push block - effectively detaching itself from the push block. Screwed it back in and away it went.

3. I turned off the feed motor switch for some reason, and forgot to turn it back on. All the lights were on, but with the motor off, no coal. Turned it back on and it was fine.

Other than that, I've had it going for ten years of its 25 or so years. A few questions for you:
Is the stove new to you?
Did it work previously?
Have you changed/replaced/cleaned anything on it since the last time that it worked (if it did work previously)?
Does the feed motor come on?
Does the cam off of the feed motor turn, does it make the hoop that it rides inside go up and down?
What settings are you using for the timers? I am currently using 2 ON, 12 OFF (while it's warm out) and 15 Extend.
How far does the push block travel? I usually have mine at 3/8". I measure the dangly thing (I know that thing has a name, but it escapes me) with a ruler as it runs.

Give us a bit more information about what's going on, and we're happy to help. This stove is very similar to a Harman Magnum, so there's a lot of help here.

Careful letting it run thinking it will free it's self.
It can/will spread the "Y" fork open to the point that it can never push coal until jam is cleared and fork is repaired/replaced. This was a common issue w/ these stoves and the Magnums and has been discussed often.
SEARCH...Harman fork

McGiever:

The ST8-VF8 uses an oval, closed loop instead of a Y fork. So, on one hand, it doesn't spread, on the other, if there's a jam it simply fries the feed motor rather than bend something that can be bent back into shape.

Either way, your advice is well placed.

Horace thanks for the manual, its a start. my stove is used and I can't say when it last worked. I can tell you everything appears to be working. my stove has an oval not a "Y". the problem is the pusher does not push the coal up to the fire pan. the pusher block is pushing but it appears that the coal is getting under the block and ground to a powder. you can hear the coal being ground. is there an adjustment for down pressure on the block? can the block be worn? the coal I am using is clean dried rice. I can get it lit initially with paper and kindling but again the coal won't push the ash off and continue to burn. I'm open for suggestions, and thanks to all for the help.

Horace, you mentioned "timers" 2 on, 12 off ,warm out,12 extend ---- ok! I'm lost.

You must remove the block and clean the area under of hardened coal dust...it can be like cement.
The motor, pusher block and slot are being abused trying to keep working in it's present condition.

Jeepers:

McGiever is spot-on. There's no adjustment for down pressure. There are instructions in the manual for the assembly of the stove; I would assume that pulling the block out is pretty much the reverse. I've never had to do it, but the manual states the put the block in through the inside of the unit.

When the feed motor is running, how far does the block travel? I measure how far the adjustment screw travels while its running. I shoot for a little under 3/8" with dry coal, and little over 3\8" with wet.

Good luck. Let us know how you make out.

jeepers64 wrote:Horace, you mentioned "timers" 2 on, 12 off ,warm out,12 extend ---- ok! I'm lost.

These timers: The three timers are under the little red screwdriver. On, Off, and Extend.
On controls for how many minutes the feed motor runs at the start of the cycle.
Off controls for how many minutes the stove will wait until the cycle restarts.
Extend control how long the Dist blower will run.

So, with my set-up, the feed motor runs for 2 minutes, then it "rests" for 12 minutes, then the cycle restarts. If the T-Stat calls for heat, it will feed continuously, building up a bigger fire until the T-Stat is satisfied.

Now that it's colder, I have it set for 2 On, 8 Off. Keeps a bigger fire in the stove.

That's the quick version. I'm happy to go further into the timers if you'd like.

Horace/McGiever : thanks you guys are giving me an education. couple more questions for you. my stove does not have a thermostat hooked up it has a bypass wire, does that cause a problem. the assembly manual Horace send me shows the stove totally dissembled. apparently all the parts are frozen from time, heat etc.. I am going to have to use some penetrating oil and muscle to get it apart. any problems with that ? anything else you want to throw at me is appreciated. want to be sure I've tried everything before I rip into it. again thanks

That's what we're here for

I didn't realize that your stove probably hadn't run in a while. Tearing it down is probably the best thing for it. I've never torn mine completely apart, but probably should.

McGiever is again correct about the blowers. Vacuum them out, oil them, and make sure they spin freely.

As far as the bypass wire goes, that won't hurt anything, really, but it will override the timer settings that I detailed previously. In other to words, the stove will think that T-stat is constantly calling for heat. This will cause the feed motor to run continuously. This will in turn (if your stove were feeding properly) give you a constant enormous fire and more heat than you might want. If you do not have (or don't want) a T-stat, you can remove the jumper wire and run it completely off the timers. You could hook up pretty much any two wire T-stat if you wanted to. The one that came with mine was a pretty cheap mercury from Honeywell. I replaced it with a somewhat better digital, but as long as it accurately works you're okay.

I would be somewhat reluctant to take out the grate as it is nearly impossible to find. While our stoves and the Magnum are very similar, the Magnum uses a two piece grate, ours a single (though mine is split down the middle.) They are not interchangeable, and very hard to find.

Make sure that the fines cleanout under the grates is clean and then closed. There's a handle inside the stove, under the grate, on the left, that can be pulled forward. This will open up two holes under the grate where fine pieces of ash and coal will fall. Since this can block the path of the combustion air, make sure that it's clean (or as clean as you can get it.)

Let us know how you make out or if you run into any problems in the meantime. Good Luck.

Just a suggestion to really look hard at the cupped blades on the fans. I have cleaned up a couple old units and had to very carefully scrape the hardened crud off the blades, the vac couldn't clean them off. It made a big difference in the amount of air they moved.

Good catch by Horace, if no t'stat wired...then timer setting only work.
Jumper wire across t'stat terminals will cause continuouis feed/burn...is okay only for fire starting, then remove jumper to run on timer cycle. The use of t'stat does over-ride timer only for when a call for heat from t'stat is made.

hum! I'm keeping up with you guys and believe my problem is with the "feed block" in that coal seems to be getting under it and perhaps lifting it as it attempts to feed coal in and up to fire pan. That being said I believe either the push block is wore or the push rod is bend. If that is the case to get it out it has to come out from the front(inside the stove) and that would mean removing the fire brick and the "grate". Horace has me concerned, how fragile is the grate and do I have any other choice? keep the information coming it's a big help and greatly appreciated can't thank you guys enough and it's a great forum.