Burn Cycle

[ColdHouse]

Just Spitballing here.
I assume that there is a burn cycle that happens with any hand fired stove.
Unlike a stoker that is constantly providing the correct amount of fuel, a hand fired stove gets loaded and then burns until tended.
I have had great success with minimal tending but that does not work when temperatures get really cold.

I am of the opinion that even with a hopper, the coal doesn't really deplete from the hopper until the grates are shaken. When temperatures are milder less ash gets shaken out and the fire bed is not effected that much by the new coal that moved down. Plus even if it takes awhile for the stove to get back where it was, it doesn't significantly effect the indoor temperature.

However, when the stove is burning hotter, when it is shaken, the fire bed is much thinner and nearly depleted if tending is not often enough. When the hopper disperses the coal onto the bed, there is not enough massive heat to recover the stove as quickly and without drastic measures, it could take hours to get the stove to a temperature to keep the house warm.

So it seems that even if you don't need to empty the ash pan, giving it a shake more frequently allows the ash to fall out and new coal to exit the hopper onto the fire bed. I guess if it was shaken every 15 minutes, which is unrealistic but stated to make a point, it would be like a stoker. It would keep the grates clear, and a vibrant fire with new coal always added. If you go 36 hours, the fire would be go out and there would still be unburnt coal after shaking. So shaking at some optimum time and topping off the hopper would keep the fire robust all the time.

[Sunny Boy]

My Glenwood base heater has a tall magazine that is a repro of an original mag for that stove. It holds about 25 lbs. of nut.

In about 12 hours it will use up that entire mag full without shaking the grates, just gravity feed.

After 12 hours the firebed level - which is about 50 lbs. - continues to drop even more without shaking. If left alone without shaking, it can continue to drop enough so that it needs to be built back up in layers to reach the bottom of the mag so the mag can then be refilled without smothering the firebed by dumping a lot of coal in the mag.

Paul

[ColdHouse]

My Glenwood base heater has a tall magazine that is a repro of an original mag for that stove. It holds about 25 lbs. of nut.

In about 12 hours it will use up that entire mag full without shaking the grates, just gravity feed.

After 12 hours the firebed level - which is about 50 lbs. - continues to drop even more without shaking. It drops enough so that it needs to be built back up in layers to reach the bottom of the mag so the mag can then be refilled without smothering the firebed by dumping a lot of coal in the mag.

Paul

Tomorrow I am going to look at the hopper on my Hitzer 503EZ before shaking. My suspicion is that coal will still be in the hopper and only slightly settled from where it was before I filled it. I too add 50 pounds or thereabouts. But as I shake, I watch new coal coming from the hopper onto the fire bed.

I am pretty positive the hopper is almost full before the shake because watching the firebed before and during shake I see it pretty much diminish with the new coal going on top

[ColdHouse]

I can say that this morning my stoves were not running very hot and after tending it took quite a while to get them where I wanted them. This afternoon, a shake down, ash pan dump, and new coal, and firebox nice and hot in no time.

[Sunny Boy]

Tomorrow I am going to look at the hopper on my Hitzer 503EZ before shaking. My suspicion is that coal will still be in the hopper and only slightly settled from where it was before I filled it. I too add 50 pounds or thereabouts. But as I shake, I watch new coal coming from the hopper onto the fire bed.

I am pretty positive the hopper is almost full before the shake because watching the firebed before and during shake I see it pretty much diminish with the new coal going on top

If the level in the hopper has not dropped, check to see if the firebed has "bridged" by running hot enough for the coal to fuse into a layer that will support the weight of the firebed and a not-to-tall hopper.

My Glenwood mag is narrow and tall. From grates to top of the mag is over 30 inches. The weight of that tall, narrow column of coal rests only on the center of the firebed, so it takes a lot of hot running to fuse a bridge strong enough to support that much weight of vertical column. I've been running it hotter with these really cold temps and it has a bridge that needs to be poked down around the edges of the firepot every time I tend it, or it won't clear all the ash during shaking. Just whatever loose ash is below the bridge.

A wider, shallower hopper may not have enough vertical weight of coal to push more than a mild case of firebed bridging down ???? Running it hotter with such cold weather makes the firebed hotter up into the fusion temperature range and that makes for a stronger bridge.

Paul

[ColdHouse]

If the level in the hopper has not dropped, check to see if the firebed has "bridged" by running hot enough for the coal to fuse into a layer that will support the weight of the firebed and a not-to-tall hopper.

My Glenwood mag is narrow and tall. From grates to top of the mag is over 30 inches. The weight of that tall, narrow column of coal rests only on the center of the firebed, so it takes a lot of hot running to fuse a bridge strong enough to support that much weight of vertical column. I've been running it hotter with these really cold temps and it has a bridge that needs to be poked down around the edges of the firepot every time I tend it, or it won't clear all the ash during shaking. Just whatever loose ash is below the bridge.

A wider, shallower hopper may not have enough vertical weight of coal to push more than a mild case of firebed bridging down ???? Running it hotter with such cold weather makes the firebed hotter up into the fusion temperature range and that makes for a stronger bridge.

Paul

The Hitzer is wide and shallow.

[Sunny Boy]

The Hitzer is wide and shallow.

There ya go - less vertical load. Now the question is...is the hopper level not dropping because it is bridging ?

Easy to check. Just shake the grates and using a poker pushed down into the edges of the firebed, see if the level then drops.

Paul

[Rob R.]

The ash content of the coal may also be a factor.

[waytomany?s]

The ash content of the coal may also be a factor.

A factor in the way it settles.? Like firmness?

[Rob R.]

Yes. I have some nut coal that burns to a powder, so the fire just keeps settling until the coal is all burned up. I have some other coal that produces a chunky ash that holds the shape of the coal until you shake the grates.

[ColdHouse]

Well This morning the house is 5* warmer on all levels.
I just tended the stove on the main floor and the hopper was depleted into the fire bed.
So the hotter stove temperature definitely consumed the coal and depleted the hopper.
Probably the way I usually have my stove set it never depletes because it simply isn't burning as much fuel.
I consumed 50# or so in one stove in around 12 hours twice as much as I do when I run the stove cooler.

Regardless, another notable difference is that this morning the fire bed was thick and hot. So after the shake there was a copious amount of lit coal and the stove was throwing a lot of heat. After the shake there was no unlit coal in the stove. The warm dry coal that I added will light and the stove will continue to stay hot and produce the needed heat. I figure if I didn't tend that stove now, there would be much less energy in the stove and it would have lost heat and taken a long time to get going again.

So basically tending based on the burn rate is much more critical when burning a stove hotter. If you want it to say hotter you need to keep it going hot with a nice thick bed of coals that are actively burning.

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[ColdHouse]

Update:
When I tended the stove, I did not open the damper or leave the ash pan door open. The door was only open for the time it took to empty the pan and shake the grates. An hour later, the stove looks like the picture here. I would imagine if we compare a stove with a roaring firebed to a bonfire and one that is idling to a tiny fire, keeping the bonfire going will require a lot of fuel and even after ending the fuel supply the coals will simmer for a long time. If I threw a bucket of water on a raging bonfire, it wouldn't effect it in any significant manner if I put it on the tiny fire it would extinguish it.
Point being, if running a stove at higher heat output, tend it more often and preferably before its firebed is getting depleted.

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[Greenleaf]

Using a hopper design, the level only drops slightly between services from what I noticed. It obviously drops a considerable amount upon shaking (and poking from the large front door to the bottom of the firebed)