Harman Magnum Stoker Settings

When running a Mag Stoker on a thermostat(pilot mode) is it better(more economical) to push al ot of coal for a short period with a longer rest, or push a little coal for a longer period with a shorter rest?

Does it even out in the end?

Mark

If your not using a Coaltrol, then you want to adjust the stroke such that running continuously your not dumping burning coal off the end of the grate. You set it so that the coal has completely burned within an inch or so of the end of the grate.

After you figure out where this adjustment is, you then can set the min and max settings for the pilot mode. I have seen my Mag run in pilot mode with just an inch or so of red coals at the back of the grate, which is about 1/2 # of coal per hour. My off time was about 13 to 16 min, my on time was 1 to 2 min, but your setting may be very different. Setting the maximum feed rate is critical, you don't want to dump burning coal into the ash pan.

I have always run the combustion blower continuously, it makes for more complete burning of the coal.

Hope this helps.

I am quite happy at this time running at 2 min on 12 min off pushing just about 2 dots I DO NOT run the combustion blower continuously by the end of my on cycle the coals are white hot with 8-10 in flames keeping the combustion blower running would create unnecessary stack temperatures and be hard on grates . During the off cycle the coal bed drops to a nice even red glow the live coals are 4 inches from the end of the grate and are burned nicely . I anticipate as the weather gets colder and the thermostat calls for extended feeding and combustion air I will have to fabricate a restricter plate for the combustion feed motor . As mentioned earlier this is an older magnum with no restricter plate or front draft test port and a flat roof . I don't know how old it is or when Harman introduced those options and at this time Harman still does not run or recommend a continuous combustion air feed.

In some posts I have seen stack temp reported as high as 300 degrees this is to hot as far as I am concerned, I like the stack to be hot enough to touch but too hot to maintain contact for more than a few seconds .

I sometimes get the impression some of these stoves are being forced to heat larger areas than intended and this is substantiated in some of the used stoves I have looked at in the last few months they have been grossly over heated and it is apparent in what remains of the finish and glass.

As a note I am new to stoker stoves but have been around coal fired appliances for over 25 years and have never warped cast iron components or burned the paint off of a stove .

But I'm still learn'in and this forum and the advice has been priceless in getting up and burning with the magnum

Thanks everybody

To continuously blow air on the coal or to not continuously blow air on the coal, that is the question!

I think the more important question concerning combustion blowers is whether the metal plate is properly set to not over pressurize the stove, thus sending heat up the stack. I have mine adjusted to -.02" WC in the stove and run the blower all the time. My stack temp is never over 125*F even when the grate is entirely full of burning coal. The fact that Harman added the plate is proof that they don't have all the answers.

With respect to the question on more dots VS less dots, I prefer to push more coal and reduce the timer to prevent over fire when using the Harman control. This prevents the stoker motor from overheating and seems to produce a nice even temp in the room. With a Coal-Trol on the Harman it operates with a different concept. I am still playing with that configuration and don't have any tried and true opinions. More to follow in a few days after I play some more.

AH...the dot thing the more i putz the more i question everything.

Is it really 3 dots maximum or 2 dots maximum with the Magnum. Below is my rationale:

My dot indicator moves from the left side of one dot, past another, and just past a third dot at maximum stroke, now if this is three dots, then a stroke that only goes to the middle, or second dot, is 2 dots, correct?
Then where is one dot? or half a dot? There is a missing dot.

I know I should just look in the stove, at the manometer and thermometer and screw the dots but I can't seem to let this go.

My stove pipe temps above the damper (which never seems to open) are around 125* with the stove maybe 175-200*.This is pushing what I consider 1 dot (starting at 1 dot and moving to the next). I was concerned that the stove pipe temp was too low but now I feel better about it.
Thanks Matthaus.

Also, While I have had the stove running pretty low, I have not been able to acheive -.04WC on this stove. It has been generally -.02 and up to -.03WC at a maximum. This measurement is taken without the combustion fan running(just natural draft)

As far as runing this stove on for 1-2 minutes on and 13 min off, I think my stove would go out. I have it down to maybe 3 min on and 8 off pushing 1 dot and seemed as though that was bordering on going out.

Always learning.

Pushing only one dot I think mine may also go out, it seems 1 dot keeps the "Fire Head" as I like to call it too far back on the grate the best airflow is achieved just over the hump and to the end .

I think I have the same thing as you with the dots, I look at where it stops and consider that Zero and count from there, I have it adjusted so the Fire Head is at mid grate, I get a good burn at that point and it gives the coal sufficient time to travel the length of the grate for a good clean burn thru the ups and downs of the combustion cycle . My coal was also a fresh delivery and was a bit damp it is drying nicely in the bin in the basement and I expect I will get the flow/push adjustment dialed in more accurately when the coal is all dried out

Cycling the fans like this the unit has only once called for a thermostat event and that was at a 78 deg setting for the sake of seeing what it did . The Harman has effortlessly kept the room toasty warm and the adjacent rooms very comfortable . The unit is also comfortable to be around and is not producing an uncomfortably hot area around it .

The most major problem at this point is the dog cannot get used to the fans coming on and off and the occasional drop of ashes into the pan, poor bugger hasn't had a good sound sleep in days

With my Mag I first set the stoker stroke for when she's running full blast - i.e. not pushing fire off the grate. Then I dial down the pilot timers to set the fire for when the thermostat isn't calling for heat.

Be patient and Leave a good few hours between adjustments, it's still a coal stove we're dealing with here...

Right now I'm at 2 on, 13 off. The fire sits way in the back, maybe a visible 1.5 inches. I am using the original controller, and it's still mild here, so I just want it "warm" in the a.m.; the thermostat might kick on briefly, not quite enough to get the fire up to "full burn".

Once the cold settles in, I'll dial up to maybe 3 or 4 on, 10 off. That keeps the pilot mode warmer, and she'll "ramp up" a bit easier when the t-stat calls. Then when it gets really cold, she'll run on the t-stat more than the timer and I'll have fire to within not quite an inch of the edge more often.

This fall I'm trying the blower-on-always trick to see what happens. The jury's out yet, but the fire looks nicer (bright orange, with blue flame maybe 1/2 the height of the firebricks) and my ashes seem more "crumbly" and look more like ashes. Last year in pilot mode my ashes still looked like the rice coal, and if I crushed some, there was still a little black coal on the inside.

I'll be curious to see what kind of a difference I get once the stove runs hotter and longer, I haven't seen her over 325 yet this season.

Well, I have now been running the stove with the combustion blower on all the time and I have found that there does not seem to be any "chocolate chips(unburned coal?)" in the "ash cake". Last week when I ran the combustion blower on the pilot mode and it would cycle on and off, I saw chocolate chips in the cake. Chips could have been shale I suppose. Just seems odd that as soon as I switched the combustion blower from part time to fulltime the chips went away.

I still have not had time to putz with the ole "more coal less on time" and " less coal-more on time"

Probably do this over the weekend when I have time to muck around with it

Mark

I'm wait'in to see what Dutchman thinks

Got my Dwyer this week and I'm gonna mess with it all saturday, it got colder this week and I bumped it up to 3 mins on Alls well.

I have my Harman running on the Coal-trol now. It is way more efficient than when I was playing with the timer and the dots. I have the feed rate set to 2.5 dots and the Coal-Trol set to 5 min and 87 max. It has been sitting there keeping the garage (15 ft ceilings, 900 Sq. ft. with open gaps in ceiling) to 65 * F minimum (went up to 76 the day we had 50 degrees outside).

I have run it from Sunday morning up till today and just emptied the ash pan (it wasn't even full). Started out running the rice and then switched to buck yesterday. It used about 25 pounds per day of rice and seems to be using a bit less buck. The fire is a nice narrow band with 2" blue flames. The stove draft is -.04 WC and the flue draft just above the stove is -.05" WC. I have checked the adjustment at both high and low fire and the combustion air plate setting is suitable for both (about 1/3 open or 2/3 covered how ever you want to look at it )

So in answer to the original question, more dots less feed time is better. I based this on how I am running the stove using the Coal-Trol which is set at almost maximum stoker stroke and while running the combustion fan continuously (the Coal-Trol takes care of that).

Just a data point for the continued science projects.

OK, so I have been running the stove at 1 minute on 10 minutes off since last night with the combust fan running through the control box(not running all the time) pushing maximum coal (2.5 dots). This ran flawless. the fire band was right in the middle of the grate.03-.04wc.The ashes were laying nice and flat on the grate.

Today i tried running the stove the same way as above except I ran the fan all the time. The fire band made its way to the back of the stove within 45 minutes. It just burned all the coal that was on the grate. With the stove cycling off for 10 minutes in pilot mode, if left alone, the fire would have starved and went out.

I had to run the stove off pilot mode in order to get the fire going again and back to the middle of the grate.

Too much combustion air maybe? The flames were curling at the top of the stove and way over the sides of the grate.

Crap, my posts just go on and on and on. Sorry

Thoughts?

Couple questions:

Do you have the plate to regulate air into the combustion fan?

Are you measuring draft inside the stove or at the flue?

Mine runs all the way at the back on min, but the flames are nice and blue and only 1 to 2 inches. I have the plate adjusted to achieve -.04 WC inside the stove.

I always seem to forget to mention some type of setting. when posting. I do have the plate set to regulate . It is about 2/3 open.(I have a 24 ft cinderblock chimney.)I got to this setting by measuring draft at the stove breech just before the damper with the stove at maybe 400. The damper was cracking at .04 wc. I then matched the .04 wc @ breech with .04wc in the firebox just below the door by adjusting the the combustion plate.
The tolerance for WC was probably +/-.01 wc. This should be accurate enough, right?

Are you measuring the .04WC with only natural draft with no combustion fan on? This is how I am taking my measurements.

It seems like I want to have the fan running for half the off time to allow a more complete burn but not enough to burn all the coal all the way to the back of the stove.

As I type this, the fan just came on and the flames immediately are rising past the top of the penta-roof and lapping at the very top of the stove. You are getting only 1-2 in flames? This is what I got when i was pushing only a little for a longer time and it seems like the ash was burned more complete. But the flame was in the back and the ash would pile up pretty high on the grate.
CRAP another chapter

hmm

heatwithcoal wrote:Are you measuring the .04WC with only natural draft with no combustion fan on? This is how I am taking my measurements.

My combustion fan runs continously so all measurements are with fan on.

heatwithcoal wrote:It seems like I want to have the fan running for half the off time to allow a more complete burn but not enough to burn all the coal all the way to the back of the stove.

I let mine burn at the back, not sure which is more efficient, right now I'm burning less than 30# per day and heating my garage to 65* outside temps are 29* to 43* (15' ceilings 800 sq ft, 12' door opens occasionally)

heatwithcoal wrote:As I type this, the fan just came on and the flames immediately are rising past the top of the penta-roof and lapping at the very top of the stove. You are getting only 1-2 in flames? This is what I got when i was pushing only a little for a longer time and it seems like the ash was burned more complete. But the flame was in the back and the ash would pile up pretty high on the grate.

I'm not sure whether the way you are doing it is not a perfectly good alternative. Since my fan runs all the time the process stays (fire at the back) constant, when it calls for heat the flames move forward some and increase in size to touch the pent roof, but the ash is always piled high on the grate. This doesn't hurt anything, except that your grates are getting more of a work out at the back just as the coal is going up the hump.

heatwithcoal wrote:CRAP another chapter

Yeah well the science project never ends, ultimately the final test of efficiency is CO2/02 levels and stack temp (not to mention a very complex set of calculations). Since we are not measuring that this is all subjective. Of course if one way burns the coal more completely I would be inclined to run the stove to achieve that (being the cheap SOB that I am!)

Just remember it is all part of the fun!

Hi folks, been away for awhile. Wanted to get the last of my soybeans cut before the weather turns, but now that it's 50-some degrees out and heading to 60 tomorrow, guess I'll have to mow the lawn "one last time" again this weekend.

Anyhow, a few nights ago it got cold enough out for the thermostat to kick on for longer than a few minutes. Stove temp in the morning was to 550-ish, stack temp just under 200. Had long blue flame curling up out of the arched roof and just a little into the front of the firebox, the fire bed itself filled out to maybe a bit more than an inch from the edge. The ashes seem crustier than when she's idling, but after they've cooled I can grab a handfull and crush tem pretty much to powder. Still have some chips of black coal here and there in the ashes, but not bad.

I'm still not decided about the combustion blower on always or letting it cycle. It's supposed to warm up for a few days into the mid-50's and higher, so I might dump my next ashpan into a bucket, then reset the blower back onto the timer and that way I can compare apples to apples since she'll be idling more often than burning for heat.