Too Much Coal in Ashes

Hi All, I've been on the board for a few months now gathering info. and just installed a used/refurbished EFM 520 about a month ago. I just couldn't justify buying any more oil @ $4.25+ gal! Anyway, overall I think it's running well, though lately now that it's been warm I've noticed that Im getting a lot of unburned coal in the ashes. By a lot, I think the ash pan is maybe 1/5-1/4 unburned coal. Since I didn't have a lot of time to play around with settings before it got warm, I've lowered the feed/air twice. I started on 5/4.5 but would always hit the high limit since I'm only heating about 1700sqft. Went to 4/4 and the stoker would run longer, maybe 20-30 minutes on a call for heat. It got warm out so I figured I'd try 3/3.25 which would make the stoker run a little longer on a call.

My other settings are: Hydrostat 3150 150 low / 200 high limit, Honeywell Timer- 2.5min every half hour

My main suspect is not enough draft, I get about .02 at idle and then when running it usually hovers around .03-.04 now that it's warm out. When it was cold when I first installed it would stay near .05. I've tried running 3 feed/3.5-3.75 air to see if it would help but it just seems that the stoker runs so infrequently that unburned coal sits on top of the ash ring and falls off the edge with it. The ashes seem clumpy /clinker but I don't think I should use any less air. I'll attach some photos of the fire at 4/4 and 3/3.25. I'll throw some in of the install too for your entertainment.

So what's a good strategy for running it in warm weather? More feed/air with shorter run times or slow and steady? I'm not going to use it for DHW this summer, but will probably add a coil eventually since electric has gone up considerably. I'm also thinking of adding a draft inducer since my chimney is an exterior masonry style and a little too short. Eventually I'll get around to making it taller but for now it's going to have to wait.

Any thoughts would be appreciated.

Nice looking EFM. I suspect the unburned coal you are observing is due to lack of demand, and the coal itself. Some coal does not burn completely when the stoker just runs on the timer, and there is the possibility your coal quality is not great.

I do not recommend running the feed at less than 4 teeth. 4/4 is a great setting for these stokers, and if the unit doesn't overheat I would just leave it there. 150/200 is fine, timer setting of 2-2.5 minutes every half hour is fine also. -.02 of draft at idle should be plenty, that is what mine runs...sometimes a little less in the summer.

It is a shame you aren't producing domestic hot water with the boiler. It would reduce your electric bill and give the unit some additional run time to keep the fire happy. In small houses, the BTU load from domestic water often exceeds the heating load.

Rob R. wrote:Nice looking EFM. I suspect the unburned coal you are observing is due to lack of demand, and the coal itself. Some coal does not burn completely when the stoker just runs on the timer, and there is the possibility your coal quality is not great.

I do not recommend running the feed at less than 4 teeth. 4/4 is a great setting for these stokers, and if the unit doesn't overheat I would just leave it there. 150/200 is fine, timer setting of 2-2.5 minutes every half hour is fine also. -.02 of draft at idle should be plenty, that is what mine runs...sometimes a little less in the summer.

It is a shame you aren't producing domestic hot water with the boiler. It would reduce your electric bill and give the unit some additional run time to keep the fire happy. In small houses, the BTU load from domestic water often exceeds the heating load.

Thanks for the reply Rob. Yeah, I'm running bagged Reading coal and with these warm days it really runs on the timer all day and a little at night. I have a log house so it soaks up heat in the day and takes a while to cool down unless it's really cold out. I'll bump it back up to 4/4 on the stoker and see if it makes a difference. Maybe the fire will get to the top of the coals faster. I definitely plan to add the DHW coil, I sort of pulled the trigger on this last minute and didn't get the coil with it. I'm glad I did though, my house hasn't been 70 in 8 or 9 years! I got the stoker from Dave up this way. Brought it home, ripped it all apart, sandblasted and painted good old Ford blue.

Still working on the outer jackets now that it's warm out and also building a steel hopper with a tapered bottom that I can eventually have a tube going outside to pour the bags in from. I'll post some pictures up when it's done.

Nick