Tuning in ye old stoker strategies

CoalisCoolxWarm wrote: ↑

Sun. Mar. 07, 2021 2:17 pm

I noticed a couple of things in your post that may help.

1. Heatilator is NOT necessary on KA6, in fact it may be bad for your chimney and draft because...

2. Stovepipe after barometric damper should easily be cool enough to touch. I can hold my hand there all day. (I watch my woodburner buddies turn green when they consider how much heat is NOT going up the chimney, LOL)

This further reinforces my earlier opinion that you have too much air blowing into your stoker bed. If your stovepipe is too hot to keep your hand on it, there is too much heat going up the chimney.

My full-time fan (the small one hanging off the rear) is BARELY open, just a sliver. My blower motor is open further, but not by much.

I'm on a medical thing at the moment, but I will be checking the ashes later today and will snap a few pics for you.

Anything else you want to see?

Wow thanks so much for your input, maybe if you could snap a pic of your fire after a solid 1/2hr-hr stoke that would be helpful. I still think/know (especially regarding your statements about stovepipe temp) I'm losing heat up the chimney but my secondary motor is open about 3/8" or less and my main shutter is actually closed. This is a duel fuel unit so it has that gate I would normally drop to almost closed for oil (it is currently completely up/open). Do you also think that burning buck is part of my problem? My ashes seem pretty decent (red and white mix and about a full ashbin per 150/lbs of coal) so I don't think I have bad coal per se. Anything else I can do to limit my air? I've used furnace cement around the entire area where the boiler meets the whole stoker+pot assembly and around the b30 secondary fan.
Keystoker told me I didn't really need a heatilator but my friend just gave me one so I figured no harm.
Also, when it's cold it pretty much stokes non-stop, I'm talking if it's less than 30'F. I'm leery to turn up the feed because that would just seem to mean a bigger bed of heat to lose more out of. Feel like I'm missing something really obvious.

I just took some pics for you. The BEST advice I have is after you open your inspection door and have the camera in one hand, do NOT reach over with your bare hand to close the door a bit from the top so you get a better pic. Three fingers on my left hand now share a "tattoo" LOL

This is at current idle. You can see the sliver I have for my constant-on fan. I tried to get you an end and underneath pic of my main blower motor setting, too.

You can see my lower and upper temps on my triple aquastat. Also my bed of coals, barometric damper, and manometer reading. My draft is running a bit on the high side, probably time to top the door and knock some fly ash and/or rust off the bottom.

It is currently 27F outside.

Here are pics while stoking on the timer (no call for heat).

The stovepipe (vertical, but it's flipped for some reason) is about as hot as water you would use to wash your hands without scalding. You *could* hold your hand on it, but probably wouldn't unless you had a reason. This is during STOKING, not at idle.

Notice the draft is a bit less while stoking. So I won't be adjusting it. This is when it counts

I also took pics of the ashes that I changed earlier this eve and pics of the fire with and without flash. You want this flame to be literally BLASTING up into the wet walls (means there is water on the other side). This is how you transfer BTUs to the water.

You do want a strong radiant fire to transfer a lot of heat while stoking.

Let me ask- did you install the bypass loop from the top output of the stoker down to the stoker side of the pump going into the bottom of the stoker? (Helps eliminate stratification and overheating when the pump isn't running.

I will be somewhere between 3.5tn - 4tn of buckwheat this year. House is 73F in the living room, 68-72F in other rooms, including the basement (without zones turned on). Still pretty leaky insulation-wise as we have some areas pretty open do to an interruption in remodel.

Hope this helps.

So what is the actual way to gauge whether you're getting good heat transfer to the boiler? Stack temp? I might be being over paranoid about efficiency and blaming things that really aren't a concern. But I'm just really struggling how to judge proper firebed and all. My draft is holding steady, right about -.02/-.015. Two guys told me to aim for bluish flames about 12" high, without a blinding coal bed....keystoker says about aiming for 2" of ash at the end of the grates but I know I'm more like 3" (although when burning actual rice it was a nice 2")

Yes, I do have the bypass loop, here's some pictures. Looks pretty BIG for being 'rice'
This is how I think it should look, but once it's stoking for a while I get more yellow flames and a much brighter bed.
Nothing crazy here
Secondary barely open
Sealed up air gaps
Shutter pretty well closed

Those are some helpful pics.

This is how I do it.

1. Don't worry about bluish flames. You have a stoker. Get the air to match the feed with a proper draft and it will burn as it was designed. Quite different than a handfired where you have a lot of chance for adjustments and such.

2. As for getting it tuned-in, the first step is your draft setting. Check, you got that. Make sure whatever else you change, you get back to this proper draft.

3. The next step is to match the burning bed to the incoming forced air. I would start by cutting your full time fan down to try to match mine. You might have to change it later, but good chance what is working in my very similar setup will work for you or at least get you a solid start. I have buckwheat, you have rice, so might be a little different.

4. Let it burn for an hour or two and settle in. Then check your stoker bed to see how much burning coal you have. I usually do 2-4 inches of ashes at the end.

When considering air vs feed, remember that too much ash is either too little feed or too much air. Too little feed and the fire "burns back" and creeps towards the hopper. Too much air and the coal burns too fast, when it should be finished burning just before it get to the end of the stoker bed (that's where the 2-4 inches comes from)

The size/area of the burning coals determines your heat transfer. The more wet-wall area that gets heat, the better the transfer.

A key difference between buckwheat and rice is the airspace between the coal. Rice has smaller spaces, which is *usually* addressed by adjusting the feed instead of the coal.

If you were to ask what I would do, I'd cut the air of the constant fan. (It's main duty is to provide "just enough air" to keep the fire from going out between burns. Plus the timer helps with this.)

Then I would adjust the feed to get the size of burning area you need.

I can also say that when I was setting up my boiler, there was a dramatic difference from "not quite right" and "dialed in" I'll bet you have the same experience.

FYI. Some people offer that with buck I could eliminate the constant fan. I haven't tried that yet. I think with rice you will need it , though.

You might want to adjust your main blower shutter to match mine, too. At least start with it and you can adjust from there. Just don't be too worried if you lose the fire until you get it adjusted. No biggie

Do you have pics of your timer settings?

Also remember the total combustion air is your main stoker fan PLUS the constant fan. Let's do the adjustments I mentioned and see what we get and can go from there.

It's possible that your constant fan is too high, it burns up all the coal before the stoker kicks on and gets a chance to burn it. The goal is to reverse that problem and take it from there.

BTW, roughly what area do you live? If you're near, you are more than welcome to come see my setup.

Retro_Origin wrote: ↑

Mon. Mar. 08, 2021 7:39 pm

So what is the actual way to gauge whether you're getting good heat transfer to the boiler? Stack temp? I might be being over paranoid about efficiency and blaming things that really aren't a concern.

Heat transfer has to do with how the boiler is designed. Nothing you can to to change that except keep the boiler walls clean.

Retro_Origin wrote: ↑

Mon. Mar. 08, 2021 7:39 pm

But I'm just really struggling how to judge proper firebed and all.

Your over thinking this, it's simple. When the stoker is on a long heat call, 30 minutes or so, you will have a bout 2" of ash and the rest of the grate should be burning coal. If the ash is much greater than 2", turn the feed up, or turn the air down. Repeat until you get it right. This may take a few days due to the nature of a coal fire burning slowly and adjustments need time to truly take effect.

Basically, you set the feed rate to match your heating load (pounds per hour). Then you adjust the air setting until you get that 2" ash band near the end of a long heat call (at least 30 minutes).

Additionally, if your chimney drafts well enough, you can unplug that secondary fan and close the shutter. You don't need it.

-Don