bad burning EFM stoker

I have a EFM Stoker boiler I purchased used and installed to heat my home and garage. It has work flawlessly since I installed it 3 years ago. I serviced it at the end of each heating season. This year I had a problem with stones in the coal. I sheared off a couple shear pins and on new years eve I broke the pot worm in the bottom of the fire pot. Couldn't get a new one on the holiday so a friend came over and we welded the worm and installed it to get heat. Now the boiler seams to have a problem keeping the fire hot enough. I also have a pie shapped dark spot in the pot and I don't get a complete burn un the coal. Lots of waste. Doesn't seem to be getting enough air. I have taken it back apart and can't find the problem. Grates apear to be good no warpage and they are not blocked or anything. I have exausted all my options. Any suggestions what to do. My feed is set at 4-5 with air setting set to the manual recomendation.

It's possible that when the worm was welded, it now is not turning in a true circular motion and feeding the coal in a non-uniform manner. It's also possible that the flights are sharp due to age, which will also throw coal to one side or the other. Are the pipes tight together in the coupling; a factor that will cause worm binding if they are not tight against each other. I'm guessing that your worm is no longer turning in a concentric manner and that you have some grinding up of the coal. Do you pull the lever and empty the fines each day while the motor is running?

yes I have been pulling the lever at least once a day to empty the fines. I did notice that there is a brass bushing in the burner pot that is were the pot auger runs. Not the one on the auger itself. It apears to be rather worn. alot of play is present. Can this bushing be changed and is it availible. And I do agree with the out of round assesment. I plan to replace the auger in the spring at the end of the heating season. the pipes are tight together.

You will need a gooseneck bushing. They are driven in from the outside of the pot, after the pipe has been removed. The old bushing may need to be slotted to remove it, and driven towards the inside of the pot.

I have been out on 2 EFM 520 with bad burns this past year.The customer was pulling the lever but the flyash etc. was not falling out.It seemed to be packed in and would not drop.

Was the customer pulling the lever while the fan was turning? Once a day? Did you look underneath to see if the clean-out cover was opening all the way. This is adjusted by moving the eye in or out?

If you have dark spots in your fire and unburned coal in your ash the problem can be in your grate.I had a similar problem that baffled me for some time til I figured it out.Let your fire go out and empty all the ashes out of the grate.You will notice that there are very small air holes in the grate that can become blocked and in some instances where inferior coal is the problem they even glaze over and are completely blocked.Make sure all the holes are open.The holes that are glazed over can be cleared by carefully chipping the glaze off with a small pointed hammer.A welders hammer is ideal.This grate is cast iron so if you use a hammer do it gently.Coaldude