Harman Magnum Stoker Timer Settings/Setup

The house that I bought years ago came with a Harmon Magnum (I think) stoker. I love the thing and the heat that it gives (and the lower cost of coal). I think that I've gotten the hang of it - it's a stoker, for pete's sake - but I'm wondering where other Magnum owners have their stoves' timers set. I read the recommendations in the user's guide and I'm way off of them. Working left to right, I have it set for 3 minutes on, 15 minutes off, and 11 or 12 extended (for the distribution blower). However, at the advice of an Uncle with the same stove, I have the combustion and distribution blowers on the same receptacle, so the combustion blower runs for 11 or 12 minutes as well. This seems to work a little better at getting the coal to burn completely, but, by my way of thinking, if you're running the combustion blower nearly constantly, isn't that pushing a lot of heat up the chimney?

Along with this, it would probably help me to know how long the stroke of your stoker is. That is, how far does the push-block travel. I have mine at 3/8".

I seem the get quite a few nearly-burned and not at all burned pieces of coal in the ash pan. From reading here, I see that this is common with stokers. Any advice on getting this better on a Harman?

Any feedback is greatly appreciated. I don't think that I'm doing it wrong, really, but I'm wondering if there is a better way.

Thanks!

Most stoker stoves are setup to run the combustion blower all the time, it give a better complete burn of the coal. Instead of on/off. However the stoker (Idle/Pilot) circuit will stoke it every so often so you don't have a flame out.

Really? That's good to know, and a bit odd, really, considering Harman's recommendations would have the combustion blower only going for half the time - only when the stoker is feeding coal. I fiddle with the settings constantly, particularly during the warmer months, in a effort get the most bang for my buck. I guess I'm more right than wrong. Someone else told me to keep everything running constantly, and then adjust the feed rate. That sounds like what the Coal-Trol does but automatically, and much more accurately.

Thanks for the reply.

My Harman ran MUCH better when I set the combustion blower to run all the time. I had the timer down to 1 or 2 minutes on and maybe 15 minutes off. I don't remember exactly....

Once you set up your combustion blower to run continously, then the coal fire will always have enough air to burn well.. then, if you still have black, unburnt pieces of coal in the ashes,, try a different source for your coal..
Some coal sources add some reclaimed coal to the mix, read the 'coal quality from different sources' thread, it has lots of info on this subject..
I've noticed a big difference in the amount of unburnt coal in my ashes, depending on where I bought my coal.

Greg L.

Check out this thread, it discussed the blower settings, same stoker I think

Extra part for vf3000

I echo what Greg and beatle said- I noticed a big improvement with more complete burning of the coal when I set the combustion blower to run constantly last winter. In the beginning I could grab a handful of ash, crush it a little, and find all sorts of unburned coal. After changing the blower setup, I got a much more complete burn.
So, the stoker and distribution blower I plug into Harman's control box, but the burner blower is now directly on a "live" outlet. I back off the pilot mode timer towards the end of the season (3 on, 13 off I think, not sure), but during deep winter I turned the burn time up a few minutes to keep the stove a little warmer during idle. The stroke I have set to push enough coal (at a full burn) for an inch or two of ash at the end before it falls off into the ash pan.

As an aside, I put the receptacles for my Mag on a common switch, so I can kill the whole stove for a few minutes without reaching back to pull plugs when changing ashpans or doing the weekly fly ash cleanout. It cuts back quite a bit on the dust I think.

Fantastic! Many thanks to everyone for your replies.

Greg: I switched coal suppliers after the first year because of price, and noticed that the coal burned much more completely. I never realized that there was that much of a difference in suppliers until I landed on this site. I'll keep researching and making inquiries of the dealers around here.

Coalmeister: Thanks for the link that I missed completely. It's a different stoker, but the information was dead on.

Dutchman: First year, I made the rookie mistake of pulling out the ash pan while the distribution blower was running. Ash all over the place. Haven't made that mistake again (yet). Coalmeister's link brings up another question: I'm assuming that you have the same stove. Mine did not have a restrictor plate on the combustion blower (the stove came with the house). I "fabricated" one and stuck it on. Do you use one and, if so, where do you set it?

Thanks again to everyone for their replies. Wish I had some knowledge to share in return, but you guys are far and away beyond me.

"Mine did not have a restrictor plate on the combustion blower (the stove came with the house). I "fabricated" one and stuck it on. Do you use one and, if so, where do you set it?"

Highlander runs the combustion fan when idling and uses a ceiling fan control to dial back the fan RPM instead of using the cover. I will send you a PM on it.

Horace- the plate is just a round piece of lightweight sheet metal, slightly more in diameter than the intake to the squirrel cage on the blower. It's attached to the blower housing by a single screw, which allows me to pivot the plate infinitely between fully closed to fully open, and holds the plate in place.

Originally, I set the blower by feel (read: wild guess ), using the flame height as a reference. Last year I spent the roughly $30 and ordered a Dwyer Mark II manometer, mounted it to the wall behind the stove, and followed the Harman manual to set the barometric draft and blower. If you need the manual, you can download it from Harman's website: http://www.harmanstoves.com/doc/magnumstokerm.pdf. It's not long on details, but it gets the point across.

The idea of dialing back the blower rpms instead is kinda growing on me , but I have not actually tried that yet. That might be one of my experiments later this year...

Dutchman:

I fabricated mine out of cardboard. Probably not the safest thing in the world, but read on.

At the very good advice of Coalmeister and Highlander, I installed a paddle fan speed control on my combustion blower. So far, so good! We had a few pretty cool nights here, but the stove didn't go off idle very often. Usually when the weather is like this, I get a lot more unburned coal in the ash pan. Running the comb. blower full time, even at the lower speed (which equates to the same thing as restricting it) I have yet to find an unburned piece.

I always had several issues with restricting the combustion blower. First of all, until recently, I didn't understand why I would want to do so. Newbie mistake, now I understand why. My biggest issue with it was running the blower at 100% and then restricting it by 90%. The blower is actually working harder (I think) because of the additional resistance and friction caused by the restriction. This will, therefore, run the motor hotter and reduce its life. It's also noisier.

When I ran it at 100% with restriction, I could barely touch the motor because it was hot. Running it with the speed control at what I'm guessing is about 20% allowed it to cool to the point where I can touch it. I have to believe - and there's probably someone out there who knows motors who can confirm or dispute this - that if its running cooler and slower, it got to last longer. It is quieter as well. This will also reduce electricity consumption, I guess, but I can't imagine that it's all that great of a savings.

I would say go ahead and do it. I got everything I needed at Lowe's for under $30. It gave me a fun project, anyway. Coalmeister and Highlander suggested wiring it so that the blower would run full speed while stoking, then at the speed control's set speed when idle. This went right over my head (sorry, guys). I did, however take your advice and put the whole thing on a common switch. Good thinking! So I have a common switch, then a receptacle that is split (top half for the main Harman control) then the speed control manages the lower half of the receptacle. So far so good, but I shut down the stove today as it has gotten a wee bit warm to run it.

Thanks again to everyone for their replies and advice.

I fabricated mine out of cardboard. Probably not the safest thing in the world

If it didn't catch fire, couldn't have been that bad of an idea

It'll be another month (ish) until I'm ready to fire up, but the more I read from those who have tried this fan speed control idea, I might end up yet on the bandwagon. Thanks for the advice.

Thought that I would give everyone an update on my experience with a fan speed control switch. I fired-up in earnest about a week or so ago. The heat that I am getting is much more consistent with running the combustion blower all the time, and the ash is just that, ASH. Almost no more unburnt pieces of coal. If I put my hand on the distribution blower, which runs only 75% of the time, I can only keep it there for a second or so since it is so hot. With the speed control on the combustion blower running all the time at about 25%, there is almost no heat at all. Just a wee bit at the far end, and it's only warm. Again, I have to believe that this will prolong the life of the blower.

Horace wrote:Thought that I would give everyone an update on my experience with a fan speed control switch. I fired-up in earnest about a week or so ago. The heat that I am getting is much more consistent with running the combustion blower all the time, and the ash is just that, ASH. Almost no more unburnt pieces of coal. If I put my hand on the distribution blower, which runs only 75% of the time, I can only keep it there for a second or so since it is so hot. With the speed control on the combustion blower running all the time at about 25%, there is almost no heat at all. Just a wee bit at the far end, and it's only warm. Again, I have to believe that this will prolong the life of the blower.

I am considering doing this when I get my Magnum Stoker on lint this heating season. Some questions...

1. Is the combustion blower connected to a rheostat that is plugged into an outlet, bypassing the Harman controls?
2. So the harman is controlling the temp with just the stoker? Any difference in temperature variation?
3. Do you still have the restrictor plate in place?
4. Is the combustion blower quieter running at ~25% speed?
5. you mention that the distribution/convection blower runs cooler? Why would this be?

Do it, you'll love it.

1. Yes. I have "bypassed" the Harman control for the combustion blower as you describe.

2./3. Correct on temp control. The rheostat on the combustion blower is merely taking the place of the restrictor plate. The coal that comes off the grate is very nearly completely burned, particularly when going through long periods of idle time. Think of it in terms of a hand-fed stove. There is constant flow of air to the coal bed which burns the coal more completely and evenly. My idle temps evened-out after I put this in place, and when the T-Stat kicks on the fire responds much more quickly without the periods of "rest" when the coal cools down somewhat.

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 )

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.