Coalgun- Puff backs & Explosions

mine never ashes when its idling only if my acquastat is set low, my draft is somewhat weak, but i havent had any ignitions since i upped my acquastat and cracked the peep hole a little bit, if its in the 50's my draft is .02 if im lucky

dchartt wrote:mine never ashes when its idling only if my acquastat is set low, my draft is somewhat weak, but i havent had any ignitions since i upped my acquastat and cracked the peep hole a little bit, if its in the 50's my draft is .02 if im lucky

It's good to hear that you are no longer having the puff-backs! A higher operating temp and the peep hole open seem o have done the trick for you. Did you also reverse the operation of the L4006 and L4081B Aquastats?

yes i did, all around working a lot better

Just to add to my previous statement.

When it happened it was also i let the hooper run dry, the ashing lowered my ash height, and when i filled her up the new fresh coal filled the pot.

So:

1. keep a high ash bed so the fire red hot coals at opening level, not too much fresh coal. In order to do this at low temps dont ash too much.
2. keep a good draft, open the peep hole, have a good supply of make up air, make sure the door seals well when running, and make sure the tombstone is on.
3.If you run low add coal to the hopper slowly over time, so dont run low, keep it topped.
4. Dont open the door while the blower is running.

I did some wiring on my boiler today and installed a double pole, center off switch to replace the grate on/off switch. In one position the grate will run as AHS designed, whenever the ash temp falls below 120 etc. In the other position the grate will only run when the fan is running. The middle position shuts off the grate. I will monitor the boiler for a few days and report my findings. I hope this new option will eliminate my explosions. We will see.

The first test last night was successful. The fan was running and the ash temperature dropped below 120 and the grate motor operated. I cycled my new switch from the AHS grate operation, to the center off position and then to the new grate on with the fan. I will now leave the switch in the new on with the fan running setting throught today and monitor the boiler operation.

rychw wrote:The first test last night was successful. The fan was running and the ash temperature dropped below 120 and the grate motor operated. I cycled my new switch from the AHS grate operation, to the center off position and then to the new grate on with the fan. I will now leave the switch in the new on with the fan running setting throught today and monitor the boiler operation.

I think you are doing all of the AHS owners a service by running this experiment. I know several people that have older coal guns (One is actually an Eshland) with the percentage timer controlling the grate...they have never experienced a puff-back. This may or may not turn out to be a "fix", but it certainly worth trying.

Rob R. wrote:

rychw wrote:The first test last night was successful. The fan was running and the ash temperature dropped below 120 and the grate motor operated. I cycled my new switch from the AHS grate operation, to the center off position and then to the new grate on with the fan. I will now leave the switch in the new on with the fan running setting throught today and monitor the boiler operation.

I think you are doing all of the AHS owners a service by running this experiment. I know several people that have older coal guns (One is actually an Eshland) with the percentage timer controlling the grate...they have never experienced a puff-back. This may or may not turn out to be a "fix", but it certainly worth trying.

Can anybody describe the operation of this percentage timer? I have an idea of how it may function...just would like to know how it works in the coal stoker application. I have a brand new 30 minute version of this in my stash. http://www.drillspot.com/products/42750 ... ycle_Timer

My AHS S130 has the percentage timer and I have had puff backs, some fairly large. I haven't had one in two years. Made several improvements i.e. better chimney, straighter stovepipe run, tombstone flapper door and white ash rather than red ash coal. Don't think there was a single item that was the cure, just an attention to all the details hoping to improve idle draft.

It would be interesting to gather members data on their ash thickness, fire thickness and unburnt coal thickness. The only way I could think of making these measurements would to to poke a coat hanger wire in from the inspection port down to the grate. Let it there a while and then pull it out. The cherry red would be the burning coal thickness, below it the ash thickness and above the raw coal. Any thoughts if this kind of data would be useful for comparison purposes?

Yanche wrote:It would be interesting to gather members data on their ash thickness, fire thickness and unburnt coal thickness. The only way I could think of making these measurements would to to poke a coat hanger wire in from the inspection port down to the grate. Let it there a while and then pull it out. The cherry red would be the burning coal thickness, below it the ash thickness and above the raw coal. Any thoughts if this kind of data would be useful for comparison purposes?

I think data would be useful, particularly if correlated with puff back experience, and Yanche's proposal would provide a signifcant amount of data.

Question to Yanche--have you tried your proposed method? How long does the wire need to be in the burn pot? Is it easy to distinguish the three levels?

I wonder if there is a way to "calibrate" direct observation data of what is seen through the view port and whether this might provide comparable data that would be easier to collect. For example--does any one see ash when looking in the view port? If no ash is visible is buring coal visable? If burning coal is visible is it visible all the time or only shortly after the forced draft blower has run?

My answers to the direct observation question is I definitely see burning coal after the forced draft has run but it is no longer visible after a substantial period of inactivity. I don't see ash. I haven't had a puff back this year since setting the grate control SV at 120.

Observations such as the suggested ones, if correlated with puff back experience might lead to guidlines, in addition to those available in the AHS and AA manuals, as to proper adjustment of the ashing control.

I just had my first big test and NO explosion! The grate temperature had fallen to 103 and the grate did not dump ash because the fan was not running. There was a call for heat and the fan started and so did the grate motor. New coal was added to the tube and the fan kept a fire on the coal. The grate shut off when it reached 120 and the fan was still running so there were no excess coal gas left in the tube so NO explosions. I will continue to provide updates. It is too early to make any conclusions but I'm on the right track.

Bob wrote:

Yanche wrote:It would be interesting to gather members data on their ash thickness, fire thickness and unburnt coal thickness. The only way I could think of making these measurements would to to poke a coat hanger wire in from the inspection port down to the grate. Let it there a while and then pull it out. The cherry red would be the burning coal thickness, below it the ash thickness and above the raw coal. Any thoughts if this kind of data would be useful for comparison purposes?

I think data would be useful, particularly if correlated with puff back experience, and Yanche's proposal would provide a signifcant amount of data.

Question to Yanche--have you tried your proposed method? How long does the wire need to be in the burn pot? Is it easy to distinguish the three levels?

I haven't tried it yet. Too busy getting ready for turkey day. I'll try the coat hanger idea this weekend and post the test results.

I have had two explosions these past 2 days both occuring when the ash grate motor was running and the fan shut off after reaching the set temperature. I will now lower the ash dump temperature to 110 from the 120 AHS setting. I'll keep you posted.

What temp is your boiler water running between?
How high is the fire in the pot?
How much fresh coal is on top?
What is the draft?
Do you have make up air?
Is the port small hole open?

rychw wrote:I have had two explosions these past 2 days both occuring when the ash grate motor was running and the fan shut off after reaching the set temperature. I will now lower the ash dump temperature to 110 from the 120 AHS setting. I'll keep you posted.

Does your ash grate motor stop running when your fan shuts off? This seems to be a major key to eliminating the puff-backs.