General Question on Coal Feeder

I'm nowhere near an expert on how my Keystoker works, so forgive me if this is a silly question: when the combustion fan is running to heat the coal, is the feeder simultaneously continuously feeding coal to the bed? Or does the feeder only feed more coal to the bed when it senses the amount of coal currently burning on the bed isn't enough to satisfy the call for heat? I'm trying to figure out the more efficient use of the coal burning on the bed, whether I should (a) minimize the amount of coal feeding to the bed, making the combustion fan stay on more often; or (b) feed more coal to the bed so that the combustion fan runs less, but potentially pushing coal into the ash bin that hasn't fully burned off. Trial and error seems to tell me that I use less coal when the feed is higher, and if coal is continuously feeding to the bed as the combustion fan is running, that would make sense why I use less coal the less the combustion fan runs. Of course I'm sure there's also a balance where I don't want to feed too much coal to the bed, because then even more coal that hasn't been fully burnt will get pushed into the bin. Seems like with my Keystoker, less than 3 turns of the feeder doesn't give the bed enough coal, so I tend to keep it between 3.5 and 4. Any info from the experts here would be greatly appreciated!

Welcome! I’m running a Keystoker koker. What model do you have? The Keystokers are all very similar as far as I know, just different sizes/BTUs. I sounded just like you when we bought a house in 2017 with this thing in the basement and no clue how it worked. This forum has great info and very helpful people. Also, Keystoker has user manuals and videos on their website that are a great resource. When all else fails, call them. They’ve always been very nice/helpful. Anyway to answer some of your questions. When you plug the unit in, the combustion motor will run constantly. That supplies air to the grate for the coal to burn. There is a shutter on that blower to adjust the air flow but if you don’t have to mess with it don’t. They are factory set and I’ve never touched it. How are you venting out? If you are not using a chimney, then another motor that will constantly run is the direct vent or power vent motor to create draft. The wall thermostat will control the coal feed. As it feeds more coal, the fire will get hotter kicking on your convection blower. That pushes hot air around the house. Once the thermostat is satisfied, fire lowers, furnace cools, and convection stops. There isn’t a sensor in the fire box to detect coal feed. If you are cold, then slowly adjust the feed rate screw. Little bits at a time waiting an hour or more between adjustments. The other thing that will feed coal is the timer box. It should feed coal every 20 min or so just to keep the fire going when the thermostat is satisfied. This prevents it from going out. If you are getting unburnt coal in your pan or you have hot coals going off the edge, your feed rate is too high. There is more to it, but that’s the basic idea. If you have a good fire but are still cold you may need to adjust the fan limit switch. That tells the convection blower when to turn on/off. Hopefully you have a way to check draft and CO detectors. If you need more info. just keep posting. Good luck!

Thanks for the info! Best I can tell, I have a 90K BTU hearth with a chimney vent. I looked around the forum for combustion info before I posted my question, and I've seen several comments from people saying the combustion fan runs constantly as long as the stove is plugged in; I must have a rare model, because my combustion fan does kick on and off depending on where I have the thermostat set. I've tinkered here and there and noticed that sometimes if the combustion fan is heating the coal, and I turn down the thermostat even a degree or so, the fan will kick off and stop heating the coal; and the opposite will happen, if the combustion fan is off and I turn the thermostat up a degree or so, it'll kick on to start heating the coal. So there's some sort of connection between the thermostat and the combustion fan in my particular model, which from what I can tell seems to be an uncommon design. I haven't thought to contact Keystoker, so that's a great idea; I've learned a lot just from this forum, but getting info straight from the manufacturer can only add to that knowledge

Interesting. unless it's hooked up wrong? usually the combustion fan is on 100% of the time to keep the coal going. My Keystoker 90, the combustion fan is on all the time. The Convection Fan (room fan) kicks on and off with temperatures.
I know on some of the older triburner? the fan would vary in speed with feed rate, but not go off?
I would think if it shuts off, the coal can go out after a while if it doesn't kick back on within a certain time period.
is there any other controls?

My Keystoker has 2 controls, the timer box that only feeds coal for 2 mins every 15 mins to keep the fire going on idle. and thermostat to continuously feed it until the thermostat is satisfied and gets it burning good for a while, then settles back to the idle timer.

some of the older stoves only had a Rheostat for speed control/Feed and it would feed continuously, either really slow or faster.

The combustion fan kicking on and off sounds weird. That would definitely cut down on efficiency. That might be why you are getting unburnt coal in your pan. I’d definitely call Keystoker. I’m betting something is not wired correctly or you have a bad control box.

Yeah I think I'll have to call Keystoker to get to the bottom of the mystery. I've never poked around inside the stove itself, mainly because I only have the patience to tackle one issue every year one year it's figuring out how to clean the glass, another is a foolproof way to start the stove, another is trying to get as much hot air from the basement to the main floor, and now this year it's figuring out this feeder. My instinct does tell me it's working properly though, since the combustion fan does react to adjustments in the thermostat, and it also never stays off for more than 2 minutes or so to ensure the coal doesn't go out. I'm assuming for a normal modern stove, the convection fan would respond to a change in the thermostat; but in mine, if the convection fan is on and I turn the thermostat down, it won't kick off; likewise, if the convection fan is off and I turn the thermostat up, it doesn't kick on. Only the combustion fan responds to the thermostat, so until I call Keystoker, my best guess is that my model may just be an outdated inefficient design that relays the thermostat setting to the internal temperature of the stove, so that the higher the thermostat setting, the higher it tries to get the internal temperature to be, and vice versa. This cycle does lead to slight fluctuations in the room temperature though, so I'll definitely want to run it by someone at Keystoker to make sure there's not something wrong

I’d be interested in what they have to say. Keep us updated!

Any chance you could post a video of it running with you adjusting it to show what you are experiencing?

Here's a video of the combustion fan responding to the thermostat; haven't gotten around to calling Keystoker yet

It looks like you don't have enough combustion air. That fire is pitiful when the combustion fan kicked on. Have you vacuumed the fines from under the burner plate? Have you cleaned out each hole in the burner plate with a 1/8" drill or punch? Have you cleaned the fan blades on the combustion fan ( I use a brass brush)? Here's my keystoker burning...

With regards to your combustion fan operation, over the years, I've seen keystoker change how they are triggered. Older models seem to be controlled by the thermostat. Some newer models have the combustion fan running 24/7. On my 2016 kaa-4 boiler, they use a rheostat to run the fan at half power in between heat calls. On a thermostat heat call, my fan kicks in at full power. Most convection fans I've seen on here run on the temperature of the stove. That way they don't pump cool air out between heat calls.

Per the current manual, your combustion fan should run all the time...

If that video shows you at a full burn, then I agree that you are not getting proper airflow. On a full burn the tops of your flames should be touching the roof of the firebox. Do you have a magnetic thermometer on the outside of your stove? When I’m at a full burn under normal operation, I’ll get between 400 and 500 degrees. On idle for an extended period of time it may drop down to 250 or less. Does your fire ever go out completely? I would think with that combustion blower responding to the thermostat you would lose your fire on a warmer day when it is not calling for heat. You definitely should call Keystoker and verify proper functioning for that model then get under that grate for a good cleaning. Keep us updated. Good luck!

I sent a Facebook message to Keystoker over the weekend, and they responded this morning:

"The older models are wired that way. The combustion fan and gear motor only run with the timer and the convection fan will run according to the fan limit switch. It can be wired to run all the time. With the fan running all the time it will maintain a smaller idle fire and a better burn from the coal."

I followed up to ask how to rewire the combustion fan, and received this response:

"You would need to run a wire from #1 in the relay to the combustion fan. You can use the white wire that is there already."

I have to assume that makes sense to many here, and maybe it will make sense to me if I'm able to spend a day taking everything apart and figuring out what's what, so I suppose it's really just a matter of if the better coal burn is equivalent to a more efficient coal burn; in other words, if I get more hours per bag of coal used, then I'll give it a go on trying to rewire the fan.

The fire in my video wasn't at its highest; it takes about 90 full seconds after the combustion fan kicks back on for it to get the fire back to its height, but even then it doesn't reach the top of the firebox. I always assumed it was because I don't feed a lot of coal to the bed; my feeder goes up to 9 turns, but I generally keep it between 3.5 and 4. I feel like I remember it does get to the top of the firebox when I first start the stove, because I start the feed at 6 and leave it there until the room is up to temperature. I do vacuum and brush the grate at the end of every season (and also if we go on vacation and shut down the stove, I'll usually vacuum and brush before restarting the fire), but I've never cleaned the fan blades or each individual hole, so I can definitely give that a try to see if that increases the fire. The coal has never gone out; I assume either a temperature sensor or a timer kicks the combustion fan on if the thermostat doesn't trigger it during a warm stretch, but during those times, I just decrease the coal feed so that the room temperature doesn't exceed the thermostat setting.

But back to the question of whether or not rewiring the combustion fan will stretch the # of hours I get out of each bag. We keep our basement door open all winter, so the stove assists the heat pump with heating the main level of our 1400 sq ft rancher; it also keeps the finished part of our basement (roughly 800 sq ft) at 70 degrees, outside of the random minute or two here and there where it briefly drops to 69 degrees. With all that, one bag gets me about an average of 36 hours during an average winter stretch. I feel like that's pretty good, but if rewiring the fan can get me upwards of 48 hours per bag, that's definitely worth it. So that's where I'm at right now, trying to decide if taking on this project will be worth it.....

I'd suggest cleaning your fan blades and holes before rewiring... If the fan is like mine, there are two screws holding the fan shroud on. Just take it apart and brush or vacuum the blades until they are clean. The leading edge is where they get dirty and cause a decrease in airflow.

It sounds like keystoker is saying run a black wire from the #1 connection to the fan (you can use a voltmeter to make sure there is always 120v on #1) and use the white that's already there. Typically, all the whites are ultimately hooked together and you can use any of them.

I seriously doubt you'll get anywhere near that type of improvement with rewiring... Maybe a little, but nowhere near that...

Have you been oiling your
combustion motor every year? Not doing that can also decrease airflow...