The Epoch of the Axeman

 
CDF_USAF
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Post by CDF_USAF » Thu. Apr. 14, 2022 7:39 pm

Which exchanger did you choose for the hot tub?


 
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Lightning
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Post by Lightning » Sun. Apr. 17, 2022 9:12 am

CDF_USAF wrote:
Thu. Apr. 14, 2022 7:39 pm
Which exchanger did you choose for the hot tub?
It's a stainless steel 55000 BTU tube exchanger, I'll post more details when I start a thread for it :)

 
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Lightning
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Post by Lightning » Thu. Apr. 28, 2022 6:27 pm

Another 2 full ash tubs with a period of 11 days. The average temperature keeps climbing, along with the pounds of coal consumed per HDD. Broke 2 pounds per heated degree this period. Had a few really warm days with highs in the 60s 70s and 80s and one day averaging above 65 degrees.

An interesting noteworthy observation was that a full bucket of coal brought the mini bin back to level for 2 days worth of running. Meaning, it used around 20 pounds per day. I'm hoping that summertime use will be at or around that amount. Keeping the hot tub warm and heating DHW with the Axe will keep my expenses in the green by offsetting electric while there isn't any home heating demand. Also, there's the benefit of helping the basement keep dry and corrosion down to a minimum.

Other than that, the Axe has been running without incident or issue. I did move the exhaust parameter down 10 degrees to 200 so that it would get a little more ashing time. This move is to keep the fire from getting too thin. Some black rocks are starting to show up in the ash pan at 12.8% but that's bound to happen once you get into the <50 pounds per day range. About 18 pounds of unburned coal went out with the ashes basing that on anything above 9%. Considering that happened over 11 days, that's less than 2 pounds per day.

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Jkohanski
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Post by Jkohanski » Thu. Apr. 28, 2022 8:31 pm

nice, you got it humming along.

 
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StokerDon
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Post by StokerDon » Fri. Apr. 29, 2022 7:14 pm

Lightning wrote:
Thu. Apr. 28, 2022 6:27 pm
The average temperature keeps climbing, along with the pounds of coal consumed per HDD. Broke 2 pounds per heated degree this period.
Thanks for doing the pounds per heating degree day. Your numbers are very interesting and, so far, confirm what I have been noticing with my Axemans. The warmer the outside temps get, the efficiency very noticeably falls off.

-Don

 
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Lightning
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Post by Lightning » Sat. Apr. 30, 2022 12:39 pm

StokerDon wrote:
Fri. Apr. 29, 2022 7:14 pm
so far, confirm what I have been noticing with my Axemans. The warmer the outside temps get, the efficiency very noticeably falls off.
I would tend to think that this would be the case with any solid fuel burner where HDDs are being counted. As we start to have days where the temperature goes above 65 degrees there will be periods of time where the fire is being maintained and standby losses aren't contributing to any HDDs. The fuel that's being consumed during those periods gets counted into the total used. So, it gets added (mathematically) to the periods where heating IS needed, like during nighttime.. As we continue into progressively warmer days, the pounds of coal used per heated degree will climb until it doesn't make sense to track them anymore. The number will eventually become undefined, since you'd be dividing by zero heated degrees.

As for the percentage of unburned in the ashes, the ash divided by coal used will eventually plateau around 20%.. This will mean 10-12 pounds of unburned coal will go out with the ashes per 100 pounds of fresh coal going in. Which really isn't terrible..

 
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Rob R.
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Post by Rob R. » Sat. Apr. 30, 2022 12:41 pm

StokerDon wrote:
Fri. Apr. 29, 2022 7:14 pm
Thanks for doing the pounds per heating degree day. Your numbers are very interesting and, so far, confirm what I have been noticing with my Axemans. The warmer the outside temps get, the efficiency very noticeably falls off.

-Don
That is true for any boiler that maintains a fixed temperature without any regard to load. Some are better than others.

It would be interesting to compare the "efficiency curve" of a few different stoker boilers to see how they compare.


 
Jkohanski
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Post by Jkohanski » Sat. Apr. 30, 2022 6:37 pm

Agreed, i also see that the warmer out, efficiency goes down. There seems to be a point where coal being burned, to keep a healthy fire, exceeds the heating requirement. Thus, coal is being consumed at a rate that outweighs, heat needed. This is just a result of a solid fuel, vs a controllable liquid instant fuel, when required.

 
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Lightning
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Post by Lightning » Sun. May. 01, 2022 6:01 pm

Jkohanski wrote:
Sat. Apr. 30, 2022 6:37 pm
Agreed, i also see that the warmer out, efficiency goes down. There seems to be a point where coal being burned, to keep a healthy fire, exceeds the heating requirement. Thus, coal is being consumed at a rate that outweighs, heat needed. This is just a result of a solid fuel, vs a controllable liquid instant fuel, when required.
I agree. That is a very good "in a nutshell" description of what is happening.

 
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Post by Lightning » Sun. May. 08, 2022 10:32 am

Two full ash tubs that took 13 days to fill. Every "two ash tub" period is variable in length of course due to heat demand. Combined, the two ash tubs generally weigh between 55-65 pounds and I always subtract the weight of the tub itself and sometimes I let them get a little or less full. This 13 day period generated 63 pounds of ash. Of that 63 pounds, I'm figuring about 23 pounds of unburned coal went out with the ashes with 14.3% ash divided by coal used. This unburned coal is based on anything over 9%, so 5.3% of the total used (440 pounds used) is 23 pounds.

A striking consistency or possibly horse shoe luck is that I measured a small period of warm weather several weeks ago that had an average OAT of 48 degrees which is the same as this period.. the uncanny similarity is that both periods had exactly 14.3% ash divided by coal usage.. things that make you say hmmmmm :lol:

I'm down to a few buckets worth left in the bin. I have a coal delivery of 3 tons ordered for Wednesday which should get me into late fall with a lot to spare. I'll get 5 or 6 more to last the winter based on what I have left of it in October or November. Right now it's $250 per ton.

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Lightning
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Post by Lightning » Wed. May. 11, 2022 3:03 pm

So a little change of plans. I hesitantly ordered two tons of buckwheat size for over summertime instead of the pea. It got delivered today. From what I've learned in my hand fired days, the smaller coal will idle easier so I figured it might be a better choice. I'm excited to get into it and do some measurements.. :ugeek:

My guy did tack on another $5 per ton to bring it to $255 per ton delivered. But no complaints here!

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Post by Rob R. » Wed. May. 11, 2022 3:34 pm

You did read the note in the manual about additional over-fire air for buckwheat, right?

 
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Lightning
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Post by Lightning » Wed. May. 11, 2022 3:47 pm

Rob R. wrote:
Wed. May. 11, 2022 3:34 pm
You did read the note in the manual about additional over-fire air for buckwheat, right?
Thanks for the reminder. I may have to improvise that since I'm using the glass plate instead of the original steel plate with the extra secondary air hole on it. Maybe a paper clip to keep a thin gap around the plate?

I wonder if Don used any extra secondary air when he was running rice thru his Axe.

 
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StokerDon
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Coal Size/Type: Rice, Pea, Chestnut and whatever will fit through the door on the Harman
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Post by StokerDon » Fri. May. 13, 2022 10:53 am

Lightning wrote:
Wed. May. 11, 2022 3:47 pm
I wonder if Don used any extra secondary air when he was running rice thru his Axe.
Looking back to page 42 of the Axeman Anderson 1959 130M thread, we were running the fire view door which has no hole in it for overfire air.

I don't recall there being any fire problems running the Blashchak Rice. It really depends on the volatile content of your coal. I had some Direnzo Buckwheat that required a lot of overfire air due to high volatile content.

One thing to keep in mind, I found that Rice feeds slower than Pea through the Axeman auger. This is completely counterintuitive to my experience with standard augers where the feed rate increases with smaller coal. I'm still not sure why this happens.

-Don

 
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Post by Lightning » Fri. May. 13, 2022 5:02 pm

StokerDon wrote:
Fri. May. 13, 2022 10:53 am
we were running the fire view door which has no hole in it for overfire air.
Cool, that's good to know!

I discovered an outfire a little too close to bedtime last night so I cut the power. Then I thru a couple valves on the DHW to prevent cold water from circulating thru the coil and let the electric tank take over hot water duty.

So today after work I figured it would be a great time to empty out the mini bin and fill it with buck size. Then I relit the Axe, did some manual ashing and got a good ripping fire going and reset the valves so the Axe is back on for DHW. Since the Axe has made temp at 166 and shut down, it's crept up to 187 and leveled out. Which is normal after a hot burn without any heat demand.

Cause of the outfire - Either it was an odd coincidence, or maybe my shutting off of the circulator had something to do with it. I decided to shut the circ off yesterday afternoon just to see how the boiler would respond. With the circ on, the water to air exchanger stays hot. It's possible that the little bit of bleeding heat makes the boiler run just enough to help keep the fire alive. The circulator is currently back on. I'm gonna keep it on for a while. My insulating of the boiler worked well in the winter to keep the basement cooler and put that heat into the house.. but over summer it might be working against me lol.

I also sped up the ashing today to 2-3 clicks. It was in the 1-2 clicks range before. That should help keep the fire from getting too thin.

The feed tube still has pea size in it so it'll take a little while to get the buck size into the burn chamber.

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