burn pot fire not full circle

I have a EFM 520 and have been trying to fix the circle of fire in my burn pot but I just can't seem to get it back. It all started when I had a big piece of coal clog the auger and it was trying to run for hours before I came home to find it. I have cleaned all the grate holes several times, grate holes are all clear. Also cleaned the auger. After shutting down and cleaning everything two different times I still have a pie section at about seven o'clock not burning bright like it should. When I relight the fire circle looks good for the first day but the pie comes back. After these two attempts to fix my fire I removed the stoker from the boiler, disassembled it and installed all new gaskets then reassembled. Yesterday fired up for the year and the pie is back this morning. Has anyone had this happen? Can anyone offer advise to fix this problem.
Thanks,
Sperry

Mine will do something similar when it is burning rice with a lot of small pieces, and at a light load...once it gets a good 30 minute burn, the fire appears normal again. I suspect the way my burner plates fit together has something to do with it...longer timer cycles seem to help, as does larger coal. I am currently burning buck, and the fire looks perfect.

When you took the auger out for a cleaning, did you notice if there were sharp edges at the section that would be in the pot area? Uneven fire is a good indication of a worn auger or your fines cleanout isn't seating properly.

Scottscoaled
Auger edges were nice and smooth. Fines lever seems to open and close smoothly .
Thanks,
Sperry

Scott means to look under the bottom of the pot. You'll see the circular plate that the lever is actually moving. The squared holes must be fully closed when the lever is pushed back. You're losing air somewhere.

Scott & Stoker man
What I meant by smooth was that the plate was opening and closing smoothly and fully. I thought that I had inspected the fines plate thoroughly enough to determine that it's not warped. Can I do an after install inspection from under the unit? Can you feel air blowing out the bottom of the fines plate if this is the potential problem?
Thanks for your help guys!
Sperry

You might feel a small amount of air blowing out when it's firing, nothing excessive. Do you use a short pipe from a barrel? If so, is air blowing out of the end of the pipe? Is the unburned area always in the same spot?

I do have a short tube. The feed tube doesn't seem to be heating up where it exits the base and with no fumes I'm thinking it's not blowing back.
Thanks,
Sperry

problem spot is always in the same area.

stoker-man wrote:Scott means to look under the bottom of the pot. You'll see the circular plate that the lever is actually moving. The squared holes must be fully closed when the lever is pushed back. You're losing air somewhere.

My stoker does something similar to what sperry has described...but mine produces a dark spot on the right side of the pot when running on the timer for 8 hours or so. My cleanout plate is only a few years old, isn't warped, and closes tight...no air leaks as verified with my hand with the blower running, and I even checked the plate with a feeler gauge for gaps. The last two sets of burner plates I have installed in an S20 took a lot of mixing and matching to try and get an even gap between them...the set in my stoker was the worst one, even after an hour of messing with it I still had two decent size gaps on the left side (which now burns bright!).

This time of year for me Is also not always a nice circle ring.

once we get into the colder months though it all rights itself until spring again.

I will assume some of that is lack of a need of heat in the boiler and shorter run times also

About the only thing left is to check the draft in your chimney. Maybe the damper needs an adjustment. The fire depends upon chimney draft to keep it going in warmer months, along with the time setting.

Check every rope gasket for integrity. Your unit should be sealed up like a drum except for the air that comes in through the stoker. This includes base of boiler seal, ash pit door seal, feed pipe gasket. The only thing that makes your problem difficult is that it supposedly started after a rock blocked the feed pipe. This should not cause these problems.

After adjusting the plate wedges as Rob suggested most of the poor burn area is much better. Sure seems to have a much better burn with a real demand calling. Almost have the full burn back(see pic). Poor burn area is still noticeable with low demand cycling. I must still have small air breech somewhere. I had one grate that was slightly warped. It seemed that a careful reassembly seated all the grates together nicely. I'll have to put a grate on the to do list. New auger bushing also.
Manometer shows proper draft flow.

I know that the blockage started the bad burn pattern I have. Consequently, the auger was spinning in bushing for 6-7 hours straight. An uneven fire in the grates burned for 6-7 hours. I allowed the fines lever to shut abruptly. One or all of these events contributed to this air breech.

You all have been very helpful and I appreciate your suggestions.
If you have any additional suggestions, please feel free to forward your ideas.
Thanks again,
Sperry

Looks like you are making progress. What are you using for feed & air settings? Had you just restarted the fire when you took that picture? If so, let it run for a day and then put a sufficient load on it to make the stoker run for 30-40 minutes straight...the fire should be about the same size as the burner plates. If after a long burn there is burning coal on the outer ring like in the picture above, you need to increase the air setting.