Help With Harman SF250

I have an SF-250 and normally shake and load every 12ish hours. I've found it OK to shake until I see an orange glow when looking through the ash door, then load. If the bed seems low or I know I've pushed the time limit a bit, I'll throw a couple shovels on and let it get going before I shake and then load it all the way. I've noticed that, like yours, there seems to be a lot of ash in the back that doesn't shake down. Every couple days I rake the back, sides, and front with a poker to try and clear that ash out. I also modified the firebox to use full size refractory brick. It helps keep the ash in the pan when you shake it down.

Thanks for all the advice. I let the fire burn itself out until just now. I took all the ash and the little bit of unburnt coal out this morning. All the grates are moving fine. It must be clinkers or something causing an ash buildup. I have a poker with a 3 inch tip that is bent up 90 degrees. I'll use this to try to clear the back grate and poke out the clinkers like everyone said. I'll probably wait till Saturday to light it again. That way I can take my time and keep an eye on everything. I must have gotten some poor quality coal this past summer from my normal guy. I have never had problems with the back going out until this year.

Thanks again for all the stove wisdom and support.

Merry Christmas (Happy Chanukkah) Everyone.

Paul

As others have said it is ash build up. The reason is the grate action at the very back and the front of the firebox doesn't clear the ash as thoroughly as between the grates since there is only one grate edge moving there. After shake downs I would scrape the front and back of the Mark III firebox with a poker through the loading door about once per week (maybe every 3 days or so during cold snaps when burning a lot). You can easily see the fine ash dropping to the ash pan when scraping the front, the back was tougher to see just because you had to lean down while reaching the poker in. Maybe the coal this year has different ash properties than previously or maybe the firebrick in the back is roughed up enough that the ash is not sliding past it as well.

IH Cub wrote:Hello. I was hoping someone could help me with the back of my fire going out on my harman. Last night, the entire firebox was burning great. This morning, the back 4" or so of the fire looks to be out. There is unburnt coal on the back of the fire. I shake it every 12 hours until coal drop from the whole fire. Thus morning, I lost some of my fire because I shook it so much to get done coals to drop from the back of the fire.

This is the third time in the last month this has happened. My strive dealer (Deleurs back to basics) said to be sure I shake the fire enough. If I shake it any more, I won't have a fire. I have a barometric damper that is always a little open this time of year. My chimney is drafting great (no Mano), but the Baro has been pulling a little open since I restarted it last week.

I plan to let the fire burn until the rest burns out over the next day or so. I will just shake it twice a day but add no coal. I really don't want to start the stove back up again until I have an idea as to the problem. I am planning on contacting Harman because it is still under warranty. Maybe the back grate isn't shaking properly? I just don't know.

Paul

read your manual, it should not have any mpd damper on it at all, per manual- it also requires a minimum 8" flue pipe. If you are using smaller than that, it's killing the volume of air needed to fire the stove, on days with low pressure .

lose the baro, it will have more draft, and fire better. Baros by design, kill draft- why would anyone want to REDUCE draft ? That's like saying, I want to reduce horsepower in my car. Just silly. It's an airtight stove, just close the front draft controls if you want to reduce draft. If it leaks, get new door seals. Baro devices were made for oil heaters primarily, they don't work well on coal stoves, unless it is a stoker.

Harman stoves are highly efficient designs- they are already heavily internally baffled from the factory, it's like having a stove with the MPD closed already. My Mark I only has a 2" slot in the heat exchanger for exhaust. That's why they insist on no MPD damper. You'd need a chimney 50 feet long with a draw fan on it, to overcome the internal baffling of a Harman. They also have built in fixed door glass secondary air vents, so any extreme draw on the chimney, pulls through the door glass vents first, and bleeds off draft. It's like having a built in baro in the stove already.

that's why if you add the MPD and baro devices to a Harman, they perform poorly. Actually I'd not put those devices on ANY stove, I'd strive to make it airtight first. If it's airtight you don't need those useless devices. If a stove needs a baro or mpd, what that says is, the doors and draft controls are lousy and leak badly- and it needs a band aid to control draft. If it's sealed up, it will meter down to a simmer without those silly gadgets. Think about it.

here's the manual, go to page 7.

http://hearthnhome.com/downloads/installManuals/S ... 0.pdfTypes Of Chimneys

THE STOVE MUST BE CONNECTED TO ITS OWN
TILE-LINED FLUE. A MINIMUM FLUE SIZE OF 8” X 8” IS
NECESSARY FOR PROPER OPERATION.

UNDER NO CIRCUMSTANCES SHOULD A MANUAL
FLUE DAMPER BE INSTALLED IN THE SMOKE PIPE
BETWEEN THE STOVE AND THE CHIMNEY.

NO DAMPER, HEAT SAVER OR AUTOMATIC VENT
DAMPER DEVICE SHOULD BE INSTALLED IN OR ON
THE SMOKE PIPE.

I burned an sf250 for about 5 years. The Harman grate system used causes the front grates to move much more than the back grates with the equal movement of the shaker handle. A long poker with the 90 on the end is what I used to break up those clinkers in the back of the firebox. I opened the bottom door about an inch or so and the top door air about a quarter turn open to burn up the fire first. I kept a magnetic thermometer a foot from the back of the stove on the stack and waited till I got a temp of 500 to 550 then used the poker to poke the fire two in back two in the middle and two in front before I would shake the fire.this helps to break up the clinkers that tend to build up on the back of the grate system. Then fill the fire box half full and wait for my temp to come back again and add the rest of the coal and then wait again for 500 to 550 again then dampen it off. I only had a baro on it. I was heating 3400 sq. With cathederals and it worked well.I hope this has helped.

Thanks for all the advice. I just need to manually poke to help that back shaker out. I think it's okay to use the Baro. The Harman manual says on page 7 "A barometric damper may be used and properly adjusted to compensate for excessive draft only."

This time of year, my Baro is always open a little bit. I think without it my fire weight not last through the night due to overdraft.

IH Cub wrote:This time of year, my Baro is always open a little bit. I think without it my fire weight not last through the night due to overdraft.

If you want to experiment, cover the baro with aluminum foil.

Coal Cracker. I respect that you are trying to help, but I wish you wouldn't give advice without experience to back it up. Are we all wrong that we see beneficial results by using draft dampers??

While I also admire enthusiasm, a couple corrections are necessary in case someone in the future is looking for info regarding their SF-250 ....

The exhaust port on the SF-250 is listed as 6". The manual states an 8"x8" SQUARE flue liner. A 6" round flue pipe is appropriate.

If you lose the baro it will have more draft but not necessarily 'fire better'. The Harman manual specifically states to use a baro in cases where there is excessive draft so apparently they do not agree that too much draft can be controlled by their primary and secondary air controls.

Not only is the internal baffle in the Harman stoves nothing like an MPD, but the SF250 does not have the internal baffle like the Mark series, it has a spiral chamber.

You do not need to install a 50' chimney to have your Harman stove operate properly. Each install will have its own 'personality' and require different chimney heights to make it work properly and possibly a baro if draft is excessive. A manometer will give actual draft readings and should be used to set up an installation. Mine happens to be a little less than 20' tall and I needed a baro to overcome excessive draft (.1) through my Mark III in certain conditions.

The first check on a Harman stove should be to make sure the ash and loading door gaskets are sealing properly and have no air leaks so the user has as much air supply control as possible. The next check is to make sure fly ash is not blocking the flue pipe, exhaust port or impeding heat transfer to the air distribution tubes. The rest of the statement regarding dampers being 'useless devices' is installation dependent.

How can you check the door gaskets? Do you just make sure the doors close tightly on a piece of paper?

IH Cub wrote:How can you check the door gaskets? Do you just make sure the doors close tightly on a piece of paper?

Yes sir, we call that the dollar bill test. Same concept but with a dollar bill since its a little stronger.

IH,

You said you have unburned coal on the back of the fire. Is the coal burning underneath the unburned coal? With 12 hour refills I usually have unburned coal above the burning coal in the whole firebox. I usually go 24 hours between refills, so I expect unburned coal after 12 hours.

An SF-250 with a full load of coal (filled to the top of the fire brick) does not need a baro to make it through the night. It will burn 24 hours, day after day using only the draft knobs. Less heat close primary air. More heat open primary air. No excessive draft without a baro.

There was unshaken ash under the unburnt coal in the back of the stove. I talked to my stove dealer. He said to let more secondary air go over the fire (open primary knob 1 full knob and secondary/load know 1/2 turn each). He also said to poke the front and back corners of the stove once a week for help clear ash.

I have been a member here since a few months after this forum's inception I think in 2005. And I have been saying a baro on a Harman is not necessary and only reduces draft. The Harman is very tight and proper operation of the bottom damper is all that was needed. The top dampers are primarily there for wood burning.

It's funny how I was mildly critiqued and ignored when I stated my findings. It seemed at the time everyone and I mean everyone was so sure I was wrong and a barometric damper was 100% necessary. I was the Inventer of "foil your baro" statement for more positive results for the newbie. And I was criticized by senior members. I feel better now to know I wasn't incorrect in my understanding of efficient use of my equipment. Feels good to be in company of non-believers. But I am not hearing any of them now. John, where have you gone?