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

 
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gaw
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Post by gaw » Tue. Nov. 14, 2017 9:19 am

Pacowy and I disagree on the use of the secondary blower Keystoker has added to their KA6 and larger stokers. I call it Continuous Supplemental Combustion Air and it is the best thing they ever did.

My experience started with the purchase of a used older KA6 boiler, one that pre-dated the addition of the little blower. I was quite happy with my find but most people I told looked sorry for me. They said you will have nothing but trouble come warmer weather. A local plumber told me that Keystoker had a “fix” for it and if I had trouble pay them a visit and buy the fan conversion kit. Well I thought I would get this thing working without the fan, after all that is how they were made for years and all you people who can’t keep a fire in the summer just don’t know what the hell you are doing, I on the other hand am smart and I will get this thing working fine, who needs the auxiliary fan?

I installed in the fall and had this thing burning like a charm all winter long, what was everyone talking about? She works great! Well then along came the first hot day, you can feel it in the air, it is hot, heavy and stagnant, and wouldn’t you know the fire went out and I was greeted with a full tub of unburned coal. Over the course of the next few weeks I increased the size of the thimble to the chimney, adjusted the air control and increased time on the timer, exceeding two minutes of run time every fifteen minutes, all to no avail; it just could not reliably keep fire. Other than opening a hot water spigot and letting it flow 24/7 what else could I do? I was defeated.

Fast forward; I got the auxiliary fan conversion from Keystoker and installed it and lived happily ever after. The End

The auxiliary fan provide that needed air flow to keep the fire going because my draft gets too weak in the hot weather. I have a drafty old two story house and would think it should have good chimney draft but in the hot weather it goes to a -1 when Keystoker calls for a -2. Keystoker has put a metal disc on the blower that is used to throttle the amount of air going into the fire. The intake is about ¾ closed so the amount of CSCA is not much, just enough and that may differ a little from user to user depending on installation conditions. Now with a reliable idle fire I have my timer runs down to forty-five seconds every fifteen minutes. This is important because the Keystoker gearbox completes a feed cycle once every minute so I went from eight plus feeds an hour to about three, this necessarily means you will burn less coal through the summer.

For heating season I can’t say there is much or any difference. The guys at Keystoker are proud of the fact that the coal burns more complete and they believe that you my save coal over the year but my experience cannot prove much difference. The theory goes like this; when the stoker quits running the auxiliary fan keeps the fire burning a little hotter a little longer and this extra heat is going into the boiler being stored for the next heat call. When the stoker starts again you are starting with a hotter fire and run time is reduced. I think it would be very hard to quantify any savings during heating season or even if there is increased consumption as has been suggested, I just didn’t see a lot of difference in performance.

A few years ago my little fan seized up. My wife tends the stoker when I’m gone and I complained about her not letting the ash tubs fill up before removing so she would pull the tub and dump them together in the cellar right next to the motors subjecting them to a plume of abrasive dust, yes she even wiped out the stoker motor this way but this is a topic for the marriage counselor not the coal forum, anyway the blower died in late fall or winter and I just let it go, got a replacement in the meantime and put it on when the weather warmed up and I experienced my first out-fire.

In summary I would say if you plan to run a Keystoker year-round the auxiliary fan is absolutely useful and probably necessary in the majority of situations. If I was going to run it only during the heating season, say October through April or May it is probably not necessary or worth the money to add it onto an older unit. If I were installing a KA6 for Pacowy I would simply put a switch on the auxiliary fan so that he could turn it on or off.


 
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Post by memco man » Tue. Nov. 14, 2017 10:06 am

Good morning gaw I just want you to know I took your advice and bought a blower for mine I am not sure if I am going to run my KA6 in the summer or not but I figured that while I am rebuilding mine this was the time to do it I also talked to the folks at Keystoker's and they seem to think it would be to my benefit to put one on, those people are really good at what they do and also extremely nice to deal with, they also said that it was one of the best improvements that they have done to there boiler along with the DHW tunnel.

Have a good day
Memco man. Bill

 
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Post by Rob R. » Tue. Nov. 14, 2017 10:14 am

Seems like the blower with a switch is the best of both.

Thanks for sharing your experience.

 
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Post by Pacowy » Tue. Nov. 14, 2017 3:51 pm

gaw's rationale for the secondary blower appears to rest primarily or entirely on summer draft issues, while my concerns relate more to system efficiency during the heating season, so I'll talk about them separately.

From the forum and other sources I believe numerous owners of older-style KA-6's have been able to use them year-round without secondary blowers or insurmountable draft issues. If I knew of someone having the experience gaw describes I would make 2 suggestions:

- don't try to push the summer feed rate too low (through short stroke and/or timer run) or you may kill the draft. I had this happen once, even with an underfed stoker.

- check the height of the throat bar. The depth of the coal bed can substantially affect its ability to hold a fire, as seen in AA/AHS units, underfed pots and even the Harman Vertiflow. Try it at the full 2".

From gaw's description, not much improvement would have been needed to meet the draft spec. If the above suggestions and other "conventional" remedies still failed so solve the problem, I wouldn't have a big concern if a secondary blower were needed (at least with one of Rob's switches) to enable summer operations.

IMO the real problem with those units is what actually happens - as opposed to what is said to happen - when the secondary blower isn't truly needed to keep the unit operating. gaw repeats "the theory", also referenced in the Keystoker manual, that "...when the stoker quits running the auxiliary fan keeps the fire burning a little hotter a little longer and this extra heat is going into the boiler being stored for the next heat call." What the theory overlooks is that the blower keeps pushing air into basically the same coal on the grate, gradually converting it to a pile of ash, and introducing air that moves away from combustion gas temps toward ambient boiler room temps. The cooler air washes over the heat exchange surfaces and carries up the flue btu's that otherwise would remain in the boiler. If Keystoker (and other mfgr's of flat/inclined grate stokers, not to mention underfed stokers) really thought it was efficient to blow boiler room air through dead ash, they wouldn't specify ash bands that start beyond the last row of air holes on the grate. If they really wanted boiler room air in the combustion chamber, there would be no need for gaskets/cement/high temp silicone to seal the combustion chamber against air infiltration. In the end, to get back to the btu's the boiler would have held absent the secondary blower, extra coal needs to be burned to satisfy the next call for heat or aquastat low limit. It's conservation of energy, and it overrules the intuitive appeal of blowing in extra air to squeeze a few more btu's out of the coal on the grate. There will need to be some serious advances in telekinesis before you can make the btu's go into the boiler water where you want them, and not up the flue where you don't. On this basis, I believe the secondary blowers are harmful to system efficiency when not specifically justified on the basis of, e.g., unique summer draft situations.

Mike

 
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Post by Rob R. » Tue. Nov. 14, 2017 3:57 pm

To be fair, the amount of air from the secondary blower is small, and adjustable. In my mind you could adjust the blower to mimic the airflow through the coal from a chimney with strong draft.

 
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Post by Pacowy » Tue. Nov. 14, 2017 4:35 pm

Why should the draft be anything other than spec? Wouldn't a higher airflow than that defeat the purpose of the baro?

Mike

 
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Post by Pacowy » Tue. Nov. 14, 2017 4:37 pm

Does anyone know the CFM rating of the secondary blower?

Mike


 
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Post by gaw » Tue. Nov. 14, 2017 5:22 pm

Pacowy wrote:
Tue. Nov. 14, 2017 4:37 pm
Does anyone know the CFM rating of the secondary blower?

Mike
45 sans restrictor plate.

 
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Post by Scottscoaled » Tue. Nov. 14, 2017 5:58 pm

Your "theory" is so flawed it's stupid.
1. When is there ever a full grate of coal on a flat bed that doesn't contain mostly ash on the end.
2. Since when does summer time running involve the same efficiency that winter time running does.
3. Does the burnt coal ash lets the same amount of air thru it that unburnt coal does?
4. Isn' t the issue about keeping the fire going?
5. How many Keystokers have you actually ran for several years?
6. What qualifies you to second guess the factory upgrades? You seem to quote the factory specs pretty tight on other brand/models.

 
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Post by Clousseau » Tue. Nov. 14, 2017 8:56 pm

Ran my KA-6 all summer this year for the 1st time. Did not go out once in 5 months. Empty ash can once every 8 days or so. Cost me 13 lbs. of coal a day at $4/bag. That's $1.33/day for hot water 24/7. Used to turn off the coal boiler and turn on the tankless oil boiler once a day to shower,etc. Then it would be turned off after 2 hrs. until the next day. No hot water by end of day. Burning that from June 1st to Nov 1st cost me almost a tank of oil/summer. That's 1.5 gal/day x $3.60/day with hot water for only 6 hrs. or so. What's the better deal?

 
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Post by Rob R. » Tue. Nov. 14, 2017 9:03 pm

Pacowy wrote:
Tue. Nov. 14, 2017 4:35 pm
Why should the draft be anything other than spec? Wouldn't a higher airflow than that defeat the purpose of the baro?

Mike
Mike, I think you misunderstood my point. I was saying that the blower can provide the airflow that would otherwise be present if the draft was at spec...which it rarely is in the summer.

 
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Post by Pacowy » Tue. Nov. 14, 2017 11:03 pm

Rob R. wrote:
Tue. Nov. 14, 2017 9:03 pm
Mike, I think you misunderstood my point. I was saying that the blower can provide the airflow that would otherwise be present if the draft was at spec...which it rarely is in the summer.
Yes, I read your reference to "strong draft" as meaning something other than spec. The OP had described draft that was not strong but was only slightly below spec. If you intend it to replicate spec, and are talking about summer conditions that can't readily be addressed without a blower, I think we are on the same page.

Mike

 
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Post by Pacowy » Wed. Nov. 15, 2017 12:17 am

Scottscoaled wrote:
Tue. Nov. 14, 2017 5:58 pm
Your "theory" is so flawed it's stupid.
1. When is there ever a full grate of coal on a flat bed that doesn't contain mostly ash on the end.
2. Since when does summer time running involve the same efficiency that winter time running does.
3. Does the burnt coal ash lets the same amount of air thru it that unburnt coal does?
4. Isn' t the issue about keeping the fire going?
5. How many Keystokers have you actually ran for several years?
6. What qualifies you to second guess the factory upgrades? You seem to quote the factory specs pretty tight on other brand/models.
I'm guessing that your opinion isn't going to be changed by anything I say here but for completeness of the record I offer the following responses:

1. That occurs when there is insufficient air or excess feed, and hot coals are going into the ashpan. Keystoker and several other mfgrs have specific recommendations for the quantity of ash that should be at the end of the grate under load at steady state. If the grate under load at steady state is "mostly ash" (your words), it is running with excess air or insufficient feed relative to mfgr specs.

2. I have not assumed or depended in any way on any such assumption. What is your point?

3. I haven't made an independent study of that. I rely on the fact that Keystoker and several other mfgrs have recommended ash bands that start at or beyond the last row of air holes on the grate. I believe that recommendation to be reasonable in that it avoids the inefficiency of both hot coals in the ash pan and blowing cooling air through dead ash that has no prospect of producing fire. If you want to question that, be my guest, but it's hard to see how that goes anywhere.

4. The OP's issue was about keeping the fire going, and as described I don't have a problem with that if the secondary blower really is the only option for doing so. Outside of summer, the OP doesn't really make a case for needing the secondary blower. In contrast, the Keystoker manual introduces the secondary blower with a statement that its purpose is "(t)o obtain a more complete burn out of coal...". This is where my issues with it really start.

5. I have not run Keystokers for my own use. I have run three underfed stoker boiler set-ups, an underfed stoker furnace (I bought from you), three flat grate stoker stoves, a flat grate stoker furnace and a vertiflow stoker stove. These cumulatively burned approximately 250+ tons of coal for my own use, and were operated consistent with mfgr ash band recommendations. Over the years I have repaired/reconditioned approximately 6 Keystoker boilers and furnaces I have received in trade from others, including an A-150 furnace I received from you. I am highly familiar with the way Keystokers operate, as well as with the Keystoker manual and the experiences of numerous Keystoker owners as posted and discussed on the forum. Do I need more than that to offer an opinion here?

6. I believe and have pointed out how the effects of the secondary blowers are inconsistent with the recommendations of Keystoker and other mfgrs regarding ash bands and air infiltration, and have explained in detail my concerns regarding their adverse efficiency impacts.

Mike

 
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Post by gaw » Wed. Nov. 15, 2017 6:52 am

To respond to a few things, Keystoker’s draft spec is -2 or -.02, I call it -2 because that’s what my gauge reads but that is in hundredths inches of water. Just so nobody is confused. A stronger draft in a Keystoker can be problematic in that if it draws strong enough to pull air in through the hopper guess where the fire will go, it will migrate right up into the hopper and that will be a bigger headache than losing the fire. This time of year draft is a piece of cake, my 9” baro is always open. In the summer at about 80° and above that draft falls to a -1. The little blower is rated at 45cfm and with the shutter set to about ¾ closed I would guess the output is probably in the 15 – 20 cfm range. You will not lose your draft; you are not forcing feeding air into the stoker as much as you are supplementing what the draft is supposed to do.

All these arguments and theories may be true in some cases and not in others, no two houses are the same, no two installations are the same. I already explained I have an old drafty house; it breathes, a lot. It was built around 1900 and has 1900 era insulation, figure that out for yourselves. Heating zone number 1 is the house. Zone number 2 is… that’s right, this is an old house. In the heating season when the temperature is cold out I see a lot of heat calls. My fire on the grate is hardly ever less than 4” when on standby; it never gets a chance to shrink back to summer time idle fires, this combined with the good draft this time of year is why I said the secondary blower was not necessary for me for heating season use only. I could have shut it down at the first out fire and bought an electric or propane hot water heater and solved my problem as well and don’t think that I didn’t consider it. Keeping the boiler hot year round is the best preventive maintenance you can do so I am glad I went the route I did.
Pacowy wrote:
Tue. Nov. 14, 2017 3:51 pm
IMO the real problem with those units is what actually happens - as opposed to what is said to happen - when the secondary blower isn't truly needed to keep the unit operating. gaw repeats "the theory", also referenced in the Keystoker manual, that "...when the stoker quits running the auxiliary fan keeps the fire burning a little hotter a little longer and this extra heat is going into the boiler being stored for the next heat call." What the theory overlooks is that the blower keeps pushing air into basically the same coal on the grate, gradually converting it to a pile of ash, and introducing air that moves away from combustion gas temps toward ambient boiler room temps. The cooler air washes over the heat exchange surfaces and carries up the flue btu's that otherwise would remain in the boiler.
This part of your theory is a bit sketchy. If you are blowing air through the grate and it is less than the 160° to 180° that your boiler temp is I would have to say your fire went out. Anthracite is said to burn at about 900° more or less. I think I would be generous in saying that even the smallest idling fire in the summer is pushing at least 200° into the boiler heat exchange area.
Pacowy wrote:
Tue. Nov. 14, 2017 3:51 pm
If Keystoker (and other mfgr's of flat/inclined grate stokers, not to mention underfed stokers) really thought it was efficient to blow boiler room air through dead ash, they wouldn't specify ash bands that start beyond the last row of air holes on the grate.
You do have air being blown through dead ash. The grates have holes all the way to the bottom end and Keystoker calls for I believe about 2” of dead ash on the bottom edge of the grate at full fire or let’s say WOT.
Pacowy wrote:
Tue. Nov. 14, 2017 3:51 pm
If they really wanted boiler room air in the combustion chamber, there would be no need for gaskets/cement/high temp silicone to seal the combustion chamber against air infiltration.
You do get boiler room air in the combustion chamber, that’s what burns the coal. We seal everything else up to force the air to come in through the grate and the coal sitting on it otherwise the air would just take the path of least resistance witch would be all those cracks and seams.
Pacowy wrote:
Tue. Nov. 14, 2017 3:51 pm
- don't try to push the summer feed rate too low (through short stroke and/or timer run) or you may kill the draft. I had this happen once, even with an underfed stoker.

- check the height of the throat bar. The depth of the coal bed can substantially affect its ability to hold a fire, as seen in AA/AHS units, underfed pots and even the Harman Vertiflow. Try it at the full 2".
Interesting idea but I can’t help but wonder if it were only that simple why didn’t we hear of this “fix” long ago and why does Keystoker set the throat strap where they do? Too thick a coal bed will push coal over the side boards.

FWIW; I just looked at the boiler a minute ago. The stoker is not running, I am guessing 4 – 5 inches of burning coal on the grate, boiler temp is about 175° and the top of the stove pipe about 6” from the breach is 150°

Again, and I stated this before; I cannot say that I burn any less coal in the winter with the auxiliary fan but on the same note I cannot say I burned any more. In my situation no discernable differences were observed. Well insulated multi zone homes may observe something totally different. However, for year round burning to provide domestic hot water I would not do without it. If I were a plumber and had customer with an old Keystoker losing fire in the summer I would offer this upgrade satisfaction guaranteed or you money back.
Last edited by gaw on Wed. Nov. 15, 2017 11:20 pm, edited 1 time in total.

 
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Post by k-2 » Wed. Nov. 15, 2017 8:51 am

Clousseau wrote:
Tue. Nov. 14, 2017 8:56 pm
Ran my KA-6 all summer this year for the 1st time. Did not go out once in 5 months. Empty ash can once every 8 days or so. Cost me 13 lbs. of coal a day at $4/bag. That's $1.33/day for hot water 24/7. Used to turn off the coal boiler and turn on the tankless oil boiler once a day to shower,etc. Then it would be turned off after 2 hrs. until the next day. No hot water by end of day. Burning that from June 1st to Nov 1st cost me almost a tank of oil/summer. That's 1.5 gal/day x $3.60/day with hot water for only 6 hrs. or so. What's the better deal?
Yea oil is the worst choice for HW. When i was using a conventional electric WH i paid roughly $35 a month for HW. With a 4 person household. I pay about $10 a month now with a HPWH. Seems like a standard electric WH would be just a economical or more so if want to give yourself a vacation from fiddling with the stoker for the summer. I know some like to keep their stoker going year round especially if the basement is damp and the rest of the house isnt affected by the additional heat.


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