Lost Fire in Combustioneer

I got a call yesterday about 16:00 from the wife, she said the fire was out and the house was getting cool. So I left work early and when I got home I found the firebox full of unburned coal with clinkers and coke on top almost touching the heat exchanger tubes.

So I shoveled 5 gallons of coal out of there and had a look at the tuyeres and they are look about the same as they did back in the fall when I started it up for the winter. Then restarted the fire and got the house back up to a cozy 75*F

Now for the question what could cause the fire to go out? There was a good 2" to 3" of loose ash in the hearth area. I did not stir the fire above the fire bowel. There were not excessive clinkers in the firebox. The coal is 1" top and 1/4" bottom size. What is the deal?

Does that unit have a timer that runs the stoker periodically?

Sorry, I should have mentioned that.

It has a Will-Burt 341740 hold fire timer, I have it set to cycle for 2 minutes every hour and I have confirmed that it is working.

However as cold as it has been the stoker will run for about 5 minutes every 30 or so minutes just from the thermostat calling for heat.

four things cause a lost fire in a combustioneer:

1. timer failure; often the relay will fail intermittently, it's hard to diagnose because of this. Also, the switch that rides on the timer wheel will fail, often intermittently because of bad contacts as well. I keep two spares on hand at all times although I've only replaced both once on my own stoker in the years I've been using it. Different coals require different hold fire settings. For example, a good KY coal will require 1-3 min/ half hour, penn kittaning 1-3 min. every half hour, and a hard, coking, Ohio #4 requires 3-5 min every half hour.

2. Removal of loose ash. The ash should be allowed to accumulate (determined by the amount of air given the fire - more air = less loose ash, more air = less loose ash/more clinker) to about the level of the fire door or slightly below, the clinker will form below and above this level. Do not remove clinker too often; once or twice a day if extremely cold should be more than sufficient.

3. too much air under the fire/ too little draft.

4. coal feed - very wet coal or foreign objects in coal allowing coal to bridge over worm. I've only had this problem when a large piece of wood became lodged in the hopper and when feeding dripping wet coal (not really good anyway because you'll rust out your hopper and potentially crack tuyeres if liquid water makes it that far.

Thank you Berlin.

I originally had the timer set up to operate 3 min every 30 min but, found that it would over heat the house (granted that was in the fall). Then I reduced the run time to 90 seconds every half hour and then found that a lot of coke would build up in the firebox. So I set it to 2 min every hour and have not had any issues sense.

I think that part of my problem is that I have been getting coal every two weeks from the same supplier however its a little different each time.

The current coal I have seems to have more volatiles and a higher AFT along with more tendency to coke. Unfortunately my coal supplier doesn't have the coal they sell tested so I am unable to get the specs of the coal and for the time being I am unable to procure a whole seasons worth of coal at once. So I'm kind of stuck with adjusting and tweaking the air and draft.

I did see that I am getting odd looking formations of burning coke that "grow" from the retort then fall over and burn.

With a coking coal, the air has to be right on to get proper burn - yes, proper burn still means that you will get coke trees - but the idea is to adjust the air so the coke burns up w/ out building too high and make sure that the coke trees are not "hard" coke. Hard coke is what coke plants make and this type of coke occurs with coking and agglommerating coals under certain conditions in underfeed stokers - too much or too little air. Hard coke is dense and does not like to burn - it's also more uniform in appearance, you're not able to see individual lumps of coal stuck together, but, rather, a solid tower or spires w/ cracks.

Changes in coal or quality can be a real PITA; it's too bad they're not more consistant - they're probably processing whoever gives them the best price on coal and not keeping to a narrow range of properties in they're requirments.

Having said all that I said in the previous post, probably the best thing you can do to prevent outfires (esp. w/ a coking coal) is to leave loose ash in the furnace. In mild weather, I often have loose ash an inch or so above the door before I bother to remove it. In cold weather, I only remove clinker. Stir the loose ash around the retort w/ the poker after you removed clinker. You don't want the ash to pack tight. The loose ash should not be removed and should be about the level of the fire door (in very cold weather with a large heating load, the loose ash level will often go down because the hot, prolonged fire will clinker much of it, but, that's not a big deal in those conditions).

Also, you may want to further reduce the feed rate on the stoker, you want longer run times and longer cycles. I use a pulley w/ an 1-1/4" belt diameter on the motor.

Thank you for your insight.

I had another fire go out this morning but, the firebox had not filled with coal, the first thing I did was push a rod down in the hopper towards the screw to see if it had bridged over, and it hadn't . So after I got it going again, I monkeyed with the timer and have it set to run for roughly 3 min every 30 min so I will see if that helps.

I'm kind of stumped as to what is going on. I have a lot of ash in the hearth area, its still building up, the cold weather we had caused the stoker to clinker a good bit of it.

I had moved the belt over to the smallest step pully on the motor an closed the air damper all the way and that was still a little too much air. Then after about a hour I checked the fire and it had burned way down into the tuyeres, so I moved it back to the middle pully an havent tried that again. There are more ways than one to slow it down. I have thought about getting or making a larger pulley to put on the gearbox input to slow it down. However im unsure of the advantages of slowing the feed down. I think that the feed is really close to correct, but I would think that the feed is tied to how many BTUs are in the coal and how many BTUs I want the heater to make.

If the screw it turning and the fire is burning down into the retort w/ the air all the way shut, you've got feed problems in the hopper - either the worm is completely worn out (even a very worn worm will still feed coal just fine in these stoves) or you have some kind of buildup in the bottom of the hopper causing the coal to bridge.

I would also throw a new relay and timer switch at it, these things usually do fail intermittently and cause exactly the problems you're having - outfires at random times even when everything else appears ok. Once the contacts inside the relay and switch get a bit of buildup on them, it's hit or miss as to whether they will close the circuit. These parts are cheap - I've had these same experiences and I replace those two components inside the timer on every stove that I fix up.

order two of these and keep them one on hand- it will STB every few years: http://www.newark.com/omron-industrial-automation ... -J-CB-AC24

Berlin is right, I just replaced a relay in one for a neighbor yesterday, first one I ever laid hands on, very well made and simple too. It took right off and was burning well in just a few minutes.

The gear box looks almost identical to my Gentleman Janitor.

bksaun wrote:
The gear box looks almost identical to my Gentleman Janitor.

Will-burt supplied their gear boxes to a huge number of other coal stoker mfgr's. They're overall a good design, but I don't like their output shaft seal design and I don't like the fragile cast aluminum case.

Good link. I think its a good idea to have spare parts on hand. I have a bunch of brass shear pins, an a spare belt.

The fire burned down into the retort only when I moved the belt over to the smallest step on the motor. It has never burned down into the retort with the belt in the middle pully.

I thought I would wrap this thread up. After resetting the holdfire timer I haven't had any more outfires. I would like to thank everybody that offered advice to me.