My experiences converting to coal

Things seem to be real quiet on this forum lately so I thought I would post a collection of my random thoughts and experiences converting my central heat from oil to coal. It's been 2 1/2 years now and I think I am just at the point where I think all of the loose ends are tied up.

The house was originally heated with coal (cast iron radiators) so switching back was pretty simple. There was a handy spot for a coal bin right next to the boiler location so it was a simple matter of rebuilding a couple of 8-foot walls walls to contain it. I used 2x4 construction on 12" centers with joist hangers and lots of anchors in the top and bottom plates to make sure it could handle the pressure. Even so, loaded with 6 feet of coal the wall bulges by 3/8" or so. Glad I didn't go for lighter framing!

I choose a Watts 70A to temper the water off the domestic coil. It requires heat traps, a throttling valve and in my case a check valve to make it work right. And it works pretty well except in very low-flow situations when the output temperature soars close to the boiler temperature. The only time I notice it is when I am using the trickle valve in the shower . If I was doing it again I would try one of those double-throttling designs instead.

The first problem I had when I first fired it up (in January!) was not enough heat. Answer: Open the primary air damper all the way.

The second problem showed up when the weather warmed up: an irritating amount of unburned coal in the ash. Answer: Double the timer setting and cut the coal feed in half during warmer weather. The secondary combustion blower the Keystoker has will keep the fire from going out but isn't enough to keep the fire vigorous if the house isn't calling for heat for a long period of time.

I made a couple of modifications to my KA-6: insulated the top, flipped the small blower over so the oil hole is on top , reglued the ash door gasket with RTV rather than stove cement, and drilled oil holes in the stoker bushings. Also had a second flow control valve plumbed into the return line just before the connection to the bypass loop to keep the hot water from convecting out and being wasted.

Cleanout and Storage:

After the usual scraping and vacuuming, I seal up all the doors and openings and put a 60 watt heat emitter in the bottom. They last a lot longer than light bulbs (5-10 years) and are sold to heat birds and reptiles by most pet supply places. So far it has worked very well. To clean out the stove pipe, I brush it out real good, spray a baking soda, water, and dish soap solution on it and flush it out real good with the garden hose. Using soap and rinsing well makes a big difference. Corrosion has been nil since I started doing this.


Thoughts?

It sounds like you were a perfect candidate for a stoker boiler. Existing central heat, and a handy spot for the boiler and coal storage. We love pictures.

How much oil were you burning before you installed the Keystoker? Ballpark cost of the boiler & installation? I'm guessing you are already past or approaching the break-even point.

The first problem I had when I first fired it up (in January!) was not enough heat. Answer: Open the primary air damper all the way.

It seems odd that you cured the heat issue with an air adjustment and no change to the feed rate, but it's certainly possible the air was way out of whack. Did you follow Keystoker's instructions for adjusting the baro and air damper?

I choose a Watts 70A to temper the water off the domestic coil.

No more Watts mixing valves for me, I have had much better luck with the Honeywell units.

Did I mention we love pictures?

Ask and you shall receive:


I should have set the air to the max that would still have enough draft (in hindsight) - instead I set the draft right but left the air at about 2/3. I was totally exhausted after 2 days of nonstop work so I wasn't functioning at 100%. The Keystoker manual leaves a lot to the imagination.

I have the good fortune to have a 30' interior masonry chimney and a grade-level walkout 10' from the boiler too, so, yes I was the ideal candidate. I spent a little less than 5K for the boiler and 2K for installation (with me doing most of the work). Coal delivery had to be cobbed up at additional expense but I figured the payback (heating oil + propane) at 6 years when oil was $3/gallon. I figured 750 gallons/year. Payback is still a couple of years away.

Here is the heat emitter in action:

Nice job on the installation. Looks like you're on the right track!

PRengert, your payback started the second you were producing a comfortable home at a reasonable price, and as oil floats at the 3.65/gallon range, you will sure be glad you jumped on the 'coal train' as early as you did. Welcome aboard!
Please don't use the toilets when in the Station area..................

PRengert wrote:flipped the small blower over so the oil hole is on top , and drilled oil holes in the stoker bushings. Also had a second flow control valve plumbed into the return line just before the connection to the bypass loop to keep the hot water from convecting out and being wasted.

Can you provide pics of these three things? Thanks!

Sounds good to me! You've done well.

PR,thanx so much for joining and posting. Your project is just what we Coal Critters Of The Board hope to inspire and see go forward for common sense Folks. You're now a part of it. Who knows how many Folks will see your fine pictures and comments on how you designed your system. The heat emitter was a great change in thought. Thanx for sharing and making this a place of Coal Accomplishment !

Sterling40man, here are the pictures:

Stoker with drilled bushings and flipped secondary blower:

Return piping with flow-check valve (flow is right to left):

One mystery that I never solved is that the max output is nowhere near the 122K BTU that Keystoker rates it as. I am burning buck- does anyone know if the max output is different with rice?

PRengert wrote:One mystery that I never solved is that the max output is nowhere near the 122K BTU that Keystoker rates it as.

What do you think the output actually is?

PRengert wrote: I am burning buck- does anyone know if the max output is different with rice?

The answer is...it depends! In theory you would feed less lbs/per hour with buck...but the air should come through the coal bed easier as well. If you were unable to max out the feed rate with rice due to air flow, buck may allow you to reach a higher output. All other things being equal, a given stroke on the stoker should move more rice than buck...and I would expect more btu's.

EFM says that one tooth of feed on the S20 stoker feeds 2.5 lbs/hr of rice, 2 lbs/hr of buck. I have found that 4 teeth with rice is fine for domestic hot water, but when burning buck I bump it up to 5.

What are you heating with the K6? Do you have to run it hard in the cold weather?

I usually agree with Rob, but in this case I don't think the feed rate would be different to the extent it is on an S-20. On an S-20, the individual pieces of buck are large relative to the space available between the auger and the inside of the auger tube, and the smaller piece size of rice leads to less "wasted space". The overall density of buck and rice are very close, so with a larger opening for the coal to feed through, I'd be surprised if there were much difference in the effective feed rate.

To me, it seems like the low output might be related to the original comment about opening the primary air damper all the way. I agree with Rob about air flowing through buck much more easily than it does through rice. As a result, all else equal, you probably would need a lower air setting with buck than you would with rice. Too much air would tend to move the fire too far "up" the burn plate, and introduce unwanted "cooling" air into the combustion chamber. I'd suggest checking whatever guidance Keystoker supplies regarding the location of the fire on the burn plate, and trying to adjust your air to achieve that.

Mike

I heat about 2500 square feet (old and leaky construction). I have the air maxed out and with max (meaning 2" of ash at the end of the grate) coal feed I would guess 80-90K btu/h is what I am getting based on my old oil boiler netting out at 86K btu. Probably burning about 80 pounds/day in cold weather. I stopped using the setback on the thermostat as an experiment and the temperature was so much more uniform throughout the house that I left it that way.

The reason that I asked about rice is that it seems like it ought to burn faster than buck meaning that a faster feed rate would be possible.

Pacowy wrote:I usually agree with Rob, but in this case I don't think the feed rate would be different to the extent it is on an S-20. On an S-20, the individual pieces of buck are large relative to the space available between the auger and the inside of the auger tube, and the smaller piece size of rice leads to less "wasted space".

Good point on the space between the auger and tube, it makes senese that would be more sensative to coal size. I agree that a pusher-type stoker should be less sensative to the difference in size from rice and buck, but I still think you would see some difference. I think the difference (% wise) would be more noticeable at a low feed rate; especially if the stoker moves back and forth a small distance...in that case I think the rice would feed more readily than buck? At the end of the day I don't own a flatbed type stoker, so I can only speculate. Hopefully a Keystoker "pro" will chime in and summarize their experience with rice vs. buck.

Thanks for the pics PR. I added an arrow to your pic of the small blower. Is this the oil hole your talking about? I didn't think we had to oil it. As far as the bushings go.......are you going to use 3'n'1 oil? Thanks.