Coal Gun Overheating

mdhorvath · Post by **mdhorvath** » Wed. Oct. 09, 2013 7:28 pm

My brother and I both installed coal guns this summer, mine is a 500 his is a 250. The 500 is working great, drifting maybe 5 to 10 degrees after shutting off. The 250 is set to shut down at 135 but overshoots to 210. It seams to keep cooking. There are dump zones. The boiler is set on 3/8" steel shims. He's wondering if its getting too much air. Any ideas?

Post by **Rob R.** » Wed. Oct. 09, 2013 7:58 pm

Did you install a draft control?

mdhorvath · Post by **mdhorvath** » Wed. Oct. 09, 2013 8:14 pm

Rob R. wrote:Did you install a draft control?

Yes

lsayre · Post by **lsayre** » Wed. Oct. 09, 2013 8:59 pm

mdhorvath wrote:The boiler is set on 3/8" steel shims. He's wondering if its getting too much air.

Only if the draft is so strong that it can woof air up through the bed of ashes from below and then on up through the coal in the anthratube.

My S130 shuts off at 180 degrees and it rarely sets off the dump zone (which for mine is set at 215 degrees). It seems to rise to 205-210 and then hover there and then eventually slowly cool down until it fires again at 170 degrees.

I couldn't imagine letting my boiler get down to 135 degrees, as 145 degrees (give or take) is the "condensing temperature" for the flue gasses, and your flue pipes (if not the very boiler itself) will rot away from the moist/acidic condensate.

lsayre · Post by **lsayre** » Wed. Oct. 09, 2013 9:10 pm

mdhorvath wrote: Any ideas?

1) Make sure the L4006A is set up as the "operating limit" aquastat, and the L4082B is set up as the "high limit" aquastat (as this is correct, albeit being contrary to the wiring diagram, and for this I urge you to not accept my word, but rather call AHS and confirm it).

2) Bump up the dump zone to 215 or even 220 degrees.

3) Lower the ash grate motors initiation temperature to 125-130 degrees (or perhaps even to 120 degrees), to increase the amount of ash residing beneath the coal in the anthratube and thin out the fire. This should inhibit the air that is being drawn up through the ashes and into the coal.

4) Make sure the flapper is opening only about 1/4" when the fan shuts off. More that this and your over the fire air is going to be increased.

5) Make sure the flapper is resting solidly closed against the port opening to the anthratube when the fan is on.

6) Make sure the boiler has been fully de-aireated and it doesn't have a big air pocket in it.

Post by **Rob R.** » Thu. Oct. 10, 2013 4:05 am

Great checklist. I too was wondering if the controls are setup correctly.

How long has this Coal Gun been online?

mdhorvath · Post by **mdhorvath** » Thu. Oct. 10, 2013 5:43 am

mdhorvath wrote:The boiler is set on 3/8" steel shims. He's wondering if its getting too much air.

My S130 shuts off at 180 degrees and it rarely sets off the dump zone (which for mine is set at 215 degrees). It seems to rise to 205-210 and then hover there and then eventually slowly cool down until it fires again at 170 degrees.

It sounds like it's running like yours. Maybe thats just how it's going to run. As for the 135 setting, he turned it down to see if the temp would stay lower. The ash temp is at 130 and there isn't any unburnt coal in the ash. I set my 500 to ash at 115 (following your advice on previous threads) to solve my unburnt coal issues.

mdhorvath · Post by **mdhorvath** » Thu. Oct. 10, 2013 5:49 am

Rob R. wrote:Great checklist. I too was wondering if the controls are setup correctly.

How long has this Coal Gun been online?

3 weeks

Post by **coaledsweat** » Thu. Oct. 10, 2013 6:35 pm

You can''t get to much air with this design. It essentially chokes on the ash when the draft blower shuts down. I believe the fire is to large relative to the burn chamber. Stop ashing for a while and let rise up in some ash and shrink the fire in size. Your fire should break the surface on occasion. If that fixes it, reduce the ashing temperature. What works on one boiler may not work the same on another, each install has it's own happy spot.
I'm not sure if the AHS has an aquastat, but if it does, the sensing bulb must have good contact in it's well or it can be very slow to react which could cause overshoot.

mdhorvath · Post by **mdhorvath** » Thu. Oct. 10, 2013 6:42 pm

coaledsweat wrote:You can''t get to much air with this design. It essentially chokes on the ash when the draft blower shuts down. I believe the fire is to large relative to the burn chamber. Stop ashing for a while and let rise up in some ash and shrink the fire in size. Your fire should break the surface on occasion. If that fixes it, reduce the ashing temperature. What works on one boiler may not work the same on another, each install has it's own happy spot.

I was fortunate to find the sweet spot on the 500 quite quickly(at least so far anyway, winter hasn't started yet).

rwwsr · Post by **rwwsr** » Thu. Oct. 10, 2013 7:57 pm

My 260s are all up in the air from 4” to 6”, flappers set from ½” to ¾” open on idle, baros set light .02ish, dump set 215ish. Heating greenhouses with them, on a sunny day they can idle from sun up to sun down.

On a breezy day they creep up and dump every 3 hrs or so, calm day sometimes dump once or not at all. Never seams to ash on idle even with multiple dumps during the day, so I think not to much wasting of coal.

Maybe the nature of the beast (not to say I would prefer no dumps). I will live with this for the savings over other heating fuels.