Do I or Don’t I; Keystoker Boilers & Auxiliary Blowers

 
Pacowy
Member
Posts: 3555
Joined: Tue. Sep. 04, 2007 10:14 pm
Location: Dalton, MA
Stoker Coal Boiler: H.B. Smith 350 Mills boiler/EFM 85R stoker
Coal Size/Type: Buckwheat/anthracite

Post by Pacowy » Wed. Nov. 15, 2017 9:37 am

gaw, thanks for having a civilized dialogue on this. I have a few brief replies to your comments:

- Even at a number around your 20 cfm you are changing out (i.e., putting up the chimney) all of the internal air in a KA-6 approximately once every minute or 60x each hour. I believe that is far more air than would be moved through an idle stoker by a -0.02 draft. Keystoker basically confirms that when they cite the secondary blower as a way to control boiler overheating. Once you accept that the secondary blower is, in effect, turning the flue into a btu dump zone that never shuts off, you may get a better view of my efficiency point.

- If you follow the mfgr specs for steady state ash band under load, you aren't blowing air through dead ash. If you don't want to take my word, take a tape measure and measure from the last row of air holes to the end of the grate. Add a reasonable amount for the length of ash overhanging the end of the grate. When you find a mfgr who tells you the ash band should be bigger than that total dimension, please let me know.

- I'm disappointed that your reaction to my throat strap suggestion is to conjure up irrelevant reasons for discounting it. I suggested 2" because it's the max of the permissible range mentioned in the current manual. You have no reason that I can see to postulate it would put coal over the side. More generally, you described a summer draft problem and I suggested this as a potential way to address it. Resisting ideas solely because you haven't heard them before makes it hard for people to help you.

Mike

 
k-2
Member
Posts: 1744
Joined: Thu. Sep. 28, 2017 10:57 am
Location: Coal Township Pa
Stoker Coal Boiler: K2- Keystoker
Hot Air Coal Stoker Stove: Alaska Stoker Stove
Coal Size/Type: Rice

Post by k-2 » Wed. Nov. 15, 2017 12:47 pm

I have to somewhat agree with Pacowy about the added air. When ever the fan is on your blowing hot air up the flue. Over steel that must be reheated again. Its a must on high fire but not always on low fire .My boiler k-2 now comes with an always on fan. Im sure i would use more coal if i were using the newer model. It would be simple to wire mine "always on" but iv no desire to do so. Its a fix that cures poor draft but im sure at the expense of coal use. Not everyone needs always on air, but you know its a one size fits all world.

 
User avatar
gaw
Member
Posts: 4437
Joined: Fri. Jan. 26, 2007 2:51 am
Location: Parts Unknown
Stoker Coal Boiler: Keystoker KA-6
Coal Size/Type: Rice from Schuylkill County

Post by gaw » Wed. Nov. 15, 2017 11:29 pm

OK I have a few comments on your comments. I have no idea what the air flow through an 8 or 9 inch stove pipe drawing a -02 draft is, I guess someone in the HVAC industry would be able to figure that stuff out but that’s not what I do. It would be safe to say that where there is fire there is smoke so air must constantly be going up the chimney, fan or no fan. I downloaded the new Keystoker manual and as a side note I must say they did a nice job, but you are taking what they say out of context to support your argument. This is what they say about eliminating overheating.

During summer operation, the small combustion motor will force a small amount of air through grates at all times, which will cause the ash to become like powder. It also prevents the fire from going out. At the same time, it reduces the size of fire bed to approximately 1 ½” to 2” which will prevent boiler water from becoming overheated
It is a fact that a smaller fire can be maintained and that prevents the boiler from overheating. I was actually going “off label” in the summer by reducing feed to keep a smaller fire. Keystoker says do not do this, reduce timer runs but I have an old style timer and I am already at minimum so what do you do? This year I said to hell with it and let it go all summer; boiler temps averaged 40° hotter this summer and I burned 17 pounds a day average versus 12.5 in past years. Guess what I am going to do next year. But back to the heat dump via chimney; I can understand burning more coal because the feed was higher this year but why did my boiler idle at 200° - 220° this year versus the 160° - 180° I experienced in the past. All that extra heat should have been washed up the chimney. (I really would not have minded)
Pacowy wrote:
Wed. Nov. 15, 2017 9:37 am
If you follow the mfgr specs for steady state ash band under load, you aren't blowing air through dead ash. If you don't want to take my word, take a tape measure and measure from the last row of air holes to the end of the grate. Add a reasonable amount for the length of ash overhanging the end of the grate. When you find a mfgr who tells you the ash band should be bigger than that total dimension, please let me know.
Well I didn’t take your word, I went down and turned the stoker off a few minutes, scraped the grate off on the end and measured; the last row of air holes is 1” from the edge, rows are half inch apart so at 2” of ash on the grate you are blowing air through at least an inch of it. To count “overhang” as part of the 2 inches is a creative way to interpret what is not actually stated in the manual. It has been a couple of years since I had any overhang, that is caused only if you have fusion and lately the coal I have gotten does not create clinkers. Don’t forget this 2” dead ash is only for a sustained continuous run, intermittent runs will have more dead ash and summer burns will only have 1 ½ to 2 inches fire and the rest will be ash so yes, the Keystoker does blow air through the dead ash, by design and if you look at the manual you can see it in their diagrams.

The strap suggestion; so the website says they are in business since 1946, I don’t know how long the KA6 has been around in its current design but to imagine that many years passed and nobody else stumbled on this “fix” is a hard sell. If you re-read their manual you will find that they suggest the coal bed can be too deep and impede air flow. My belief is that the deeper adjustment is for buck which is coarser and lets air through it more freely. But forget all that, the Keystoker moves a bed of coal across a grate, when the coal gets to the airflow it starts to burn from top to bottom pretty much all et once and requires the stoker to provide fresh fuel to keep the fire going. How is a deeper fire going to make a difference? We all know the fire triangle; fuel, oxygen, heat; we have the fuel and the heat what we need is oxygen and the little blower provides that.

Anyhow still civil here, food fights are at FSC.

 
Pacowy
Member
Posts: 3555
Joined: Tue. Sep. 04, 2007 10:14 pm
Location: Dalton, MA
Stoker Coal Boiler: H.B. Smith 350 Mills boiler/EFM 85R stoker
Coal Size/Type: Buckwheat/anthracite

Post by Pacowy » Thu. Nov. 16, 2017 11:26 am

Sometimes even civilized dialogue needs to address arguments that try to nitpick or wordsmith their way to conclusions that depend on ignoring fundamental relevant facts. For example, you reference air flow through an 8- or 9-inch pipe under spec draft conditions as if it supports your proposition that "air must constantly be going up the chimney, fan or no fan". However, you leave out the part where the air in question has to pass through 1/8" holes that are covered with coal or ash and make up a very small fraction of the area of the burn grate. Sure, natural draft will pull a small quantity of air through the grate and up the flue, but waving your hands and pretending it's comparable to your 20 cfm estimate is pretty far-fetched. Heck, if the fan doesn't materially change airflow relative to a fairly weak natural draft, why would anyone with spec draft want one? Sorry but it seems like when k-2 reaffirmed the importance of airflow to efficiency, your first reaction was to try to create a misleading impression that the secondary blower doesn't change airflow.

On the overheating issue, I can't find any place where you have addressed the self-contradiction of the manual on the effects of the blower. Bearing in mind that we're talking about an idle boiler ("when demand cycle has been completed"), the manual states the secondary blower will both put more heat into the heating system (i.e., raising the temp of the boiler water) and prevent the boiler from overheating, relative to no blower. This may make sense to someone trying to justify use of the blower, but on its face it is inconsistent with conservation of energy. And it sure as heck doesn't account for the extra btu's going up the flue.

On the dead ash issue, the ash band guidance is offered so that the operator can control the system based on what he/she sees without shutting down the stoker and breaking out a tape measure. In my experience, spanning hundreds of tons of coal from multiple sources burned in many flat grate and underfed stokers, long runs under load typically produce some amount of ash overhang. You try to attribute the lack of overhang you have experienced in recent years to the coal you have used, seemingly overlooking two obvious other factors: (1) the fact that you have been using a secondary blower that is promoted on the basis of the way it burns out ash to powder, and (2) the fact that the past few years have seen very mild heating seasons in much/most of the northeast, during which heating systems generally were subjected to atypically light use. If all you have observed is powdered ash dropping off the edge of the burn grate, I would submit that you likely haven't been looking at the steady state to which the ash band guidance is meant to apply, so your fraction-of inch quibbling is kind of pointless. Not to mention that I provided a description of how the ash band guidance implements an optimality condition, and I don't think you've offered any explanation of how it would improve efficiency to have a stoker under load cool the combustion chamber by blowing boiler room air through dead ash. I agree that the Keystoker manual shows an idle fire profile that causes lots of boiler room air to be blown through dead ash, and that is Exhibit A supporting my efficiency concerns regarding the secondary blowers.

On the throat strap, I don't think it matters if Keystoker has been in business since 1946 or 1776. I already described how the stokers with thicker beds of coal generally can hold the fire longer than flat grate stokers with thin beds. AA/AHS units and some underfeds can be run successfully with zero or minimal timer cycles. Your comments reveal that you would rather talk about how the secondary blower is needed, rather than rotate your tape measure 90 deg and see if you, your installer, or some previous owner might have - perhaps in the name of "saving coal" - set your throat strap height low, creating a comparatively thin bed that produces both a weak summer draft and a heightened susceptibility to outfires. What's the harm in checking?

Mike


 
User avatar
gaw
Member
Posts: 4437
Joined: Fri. Jan. 26, 2007 2:51 am
Location: Parts Unknown
Stoker Coal Boiler: Keystoker KA-6
Coal Size/Type: Rice from Schuylkill County

Post by gaw » Thu. Nov. 16, 2017 6:10 pm

Well here again you are making it up and reading into something that was not said just as you go on to accuse me of. My statement was one of curiosity as to the difference in air flow not implying there was no difference. Your rebuttal did not provide me with that information so I am still left curios.

I don’t work for or have any affiliation with Keystoker so I don’t have to address any inconsistencies with their manual. I do know from first hand use that what you are doing is mixing summertime overheating with what Keystoker claims happens during heating season when the fire is larger. I said it before that I, me, my experience has shown no noticeable difference in coal usage with or without the little blower during heating season. The blower is a guaranteed fix for reliable summertime domestic hot water use and until you show me the Keystokers you fixed with your solutions I will continue to recommend the auxiliary blower for people who want to burn year round.

I measured the grate because you told me to and I knew you were wrong on that point. I have no need to measure the throat strap because what ain’t broke don’t need fixing.

No need to address your frivolous ash overhang comments but my friends and neighbor appreciate your support by burning hundreds of tons of coal, keep it up.

Again you really are fixated with that throat strap. I don’t have time to make fire every other day in the summer but please show us all that it works on your time, if you can prove it works I may even try it but until then I have something that works. One last thing, thinking that making the coal bed a bit deeper will turn the Keystoker into an EFM style underfeed or something like an Axeman Anderson is ridiculous and i hope you know better than that.

I will be traveling for a week so I doubt I will be posting on this thread during that time, using a tablet is tedious. Post any arguments you wish, I didn’t go away mad, I just went away… for a while. :out:

 
Qtown1835
Member
Posts: 705
Joined: Sat. Nov. 08, 2014 11:47 am
Location: Quakertown, PA
Stoker Coal Boiler: Keystoker '81 KA4 (online 1/16/17)
Coal Size/Type: WAS Lehigh Rice (TBD)
Other Heating: EFM SPK600

Post by Qtown1835 » Thu. Nov. 16, 2017 7:10 pm

8" flue at .01wc = 136.9cfm
According to my Google calcs.

Velocity FPM= 4005x√w.c.
4005x√.01=400.5 FPM

Xsecton area flue= r2xπ
.33x.33x3.14= 0.342sf

CFM= vel FPM x area of flue
400.5x0.342= 136.9CFM

 
User avatar
Rob R.
Site Moderator
Posts: 17980
Joined: Fri. Dec. 28, 2007 4:26 pm
Location: Chazy, NY
Stoker Coal Boiler: EFM 520
Hand Fed Coal Stove: Chubby Jr

Post by Rob R. » Thu. Nov. 16, 2017 8:58 pm

That probably assumes a straight pipe, with open ends. Sucking through a layer of coal would certainly choke things down.

Someone needs to mount a flow hood over the stoker. :D

Post Reply

Return to “Stoker Coal Boilers Using Anthracite (Hydronic & Steam)”