hand feed to stoker conversion slab heating project

Greg,
I was a little nervous about posting the pictures because it clearly shows that my boiler is very dirty. Especially seeing all those pictures of beautiful installs and clean surroundings. I started my tests dirty and feel that I should not change that till have data from my next experiment. Just came back from Lowes for an 8 to 6" reducer to test a extension in the boiler.
I noticed for what I know after reading around here an EFM boiler in the local junkyard ( fins inside). It had a rust hole on the outside but I will check if it is fixable and see how much they want for it. Are they worth something? At least I can measure it and determine the heat exchange surface area.

kevin ,
Funny enough this unit does not have one. I asked the chimney installer and he said that was not required for this wood boiler??? He sold me an AA130 for $500 and I did not want to press him about it. I have a 6" laying around and will put that one on. I think that the pipe extension lower in the boiler will help some also. I put the dwyer on this for these experiment and obvious will leave it on.

I have a vacuum switch out of a washing machine ( water level adjustment) and want to try if that could detect loss of draft so that alarm goes of. Will see.

Back to barn and experiment some more.

Thanks for the help,J

Closed the side gaps in the top plate so that less heat can escape along these side gaps. Installed 6" flu pipe to bottom. Draft over fire fan ON 0.05 and with fan OFF 0.06. I guess the next step is reducing that further but it is good that the 6" flue pipe did not affect things to badly. Stack temperature is lower again, also the bottom of my 30 degree inclined flue is significant cooler then the top side. I will follow up with some more numbers and see how it measures up to other boilers after a cleaning.

Later J

Good progress...but I might be a little more generous with the clearance between that flue pipe and the grates...it wouldn't take much flyash to create a restriction. Maybe you can just shake the grates once in a while?

If the stack temperature is lower, you are on the right track. Curious - what do you observe for an internal stack temperature after a 20-30 minute burn?

Happy New Year everyone,

Installed a draft barometric damper and set in at 0.03. It pulls full open.
Installed before the baro damper a 8" magic hat heat reclaimer.

After an hour run to bring the water on temperature:
Draft over fire ( actually right beside it) 0.025
Stack temp at exit of boiler measured in the center of the pipe 608 F
Flue temp after magic hat reclaimer with fan running 464 F

When stoker is OFF cycle draft is 0.05
Stack temp at exit of boiler 347 F.

I can not get the draft lower so I think I have to install an additional manual damper in the pipe itself.

The chimney is double wall insulated 20 ft straight up and 8 feet under 30 degrees all SS.
Later J

Your heat exchanger surface [the inside surface of the boiler] just isn't absorbing enough heat.

My AA when it first starts up will have only 200* inside flue temp,, the pipe temp is ~100. after about a 5 minute run, the flue inside temperature
may be 400-450.
I think the main reason for the temp rise is the fire is just idling when the run starts, but the fire is really stoked up at the end of the 5 minute run, the entire inside of the heat exchanger is full of blue flames.

I think you said you had an EFm Boiler to check out?? and you had bought an AA 130?? seems like you need to move on to a better boiler design

Greg L

Greg, you probably are right, thanks for your numbers , it is nice to compare. Anyhow it was a good try. The heat exchanger area of this boiler is about 20 sq feet and as a hand fed boiler rated 120 to 140000 BTU. The EFM is scrapped, oh well. I have another job for the aa130 in a rental property but there is already a natural gas boiler there so currently not that competitive.

I think I have to try to reduce the draft and still have the fan experiment and then of course as you mentioned clean the whole thing out.

Later J

joeblack5 wrote:Installed before the baro damper a 8" magic hat heat reclaimer.

I'm curious about your results with the heat reclaimer. You get much heat from it??

You would probably cut your coal consumption by at least 1/3rd if you switched to a more efficient boiler. My EFM runs an internal stack temperature of 350-375F on long burns.

JB5 do a search on the forum for EFM: Electric-Fireman Hybrid forum member europechris posted some photos of his EFM boiler, it had the 'comb' rows of ribs in the heat exchanger to increase surface area, hi posted photos of the inside of the boiler, so you cna see what it looks like.


Did you block off the gaps around the stoker in the doorway?? I'd buy a 6" 'scrub brush' with wire bristles and put it on the broom handle and wipe down the interior or the boiler, see what i a difference it makes..

GL

Evening,

Thank you for all the help and advice.

Lightning, I think it works good. The water temp is about 140, slab inlet temp 72 slab outlet temp 62. My feet are not cold, it is nice to have some extra heat blowing, not a lot on this floor area 1500 sqft plus a 1500 sqft second floor in this gambrel barn. I will do some temp measurements before and after the heat reclaimer.

Rob, you are probably right but i do like to have the possibility to hand stoke and burn wood

Greg, I studies that post, VERY IMPRESSIVE, I noticed the fins that why I new that it was an EFM in the scrap yard but is gone now.
I heard that the square area of the EFM is 22 sqft. Not much more then what I have here.

This morning I found a large build up of ashes on the K8. The rice was dropping over the side. To much air?? or to much draft with the old setup? Burned about 40LBS coal during the night.

Today I mounted a motor actuated damper in the flue pipe. The damper disk is smaller then the pipe so it always allows some draft.
This is an experiment , as the whole project is, but I felt that my draft was way to high.
With the motor damper set so that the baro barely opens the draft over fire is -0.02 with fan running and -0.035 at idle.
My ON /OFf cycle to maintain 140F water temp to heat the slab is about 1 to 4 . The flue temp before the baro in the center of the pipe is 320F On and 250 OFF. I am measuring it with a wire thermocouple and that responds very fast.
My timer is 20 sec ON 80 sec OFF . I need to get a better timer to get longer ON and OFF times. Overall I think I am getting closer to the desired temps.

The other thing I did today was lining the bottom of my coal bin with tin to make it more slippery and also prevent the bottom from rotting out over time.
This one holds 3.5 Ton of nut or I guess about 3 ton of rice. My supplier says that the rice is heavier and that it could hold 3.5 ton as volume as well . We will see the rice is coming Monday at $ 240 / ton delivered.

I did work also on the gaps and made a filler plate but there are no real seals. No cleaning yet as I still want to compare.

3.5 ton of rice does fit but it was some work to shuffle it around so that it would fit.

I have a Bacharach tester PCA25 and this is what it showed.

Stack -temp 311F
AMB.- Temp 62.0F
O2 12.9%
CO2 7.3%
CO 239 PPM
O% cor CO 621 PPm
efficiency 83.5%
ex.air 155.74
draft 0.04 WC

The fuel setting is on coal. The probe was inserted in the stack 2 feet after the breach and before the baro but after the economiser.
I tweaked the air flap to the lowest CO level. It seems that is pretty sensitive. I would have thought more air would mean less CO but that is not the case , at least according the instrument. Can anyone with more experience please chime in on these results.

Thanks J

I think your results are excellent.

Thanks Rob,

I am no expert on a flue analyzer, the efficiency is probably the combustion efficiency may be not the overall efficiency in how much hot water energy I get out of the boiler. Here is an interesting link I found in the mean time. http://www.habmigern2003.info/216_combu ... eters.html
You were right about that extra space needed so the ashes would not plug the 6" pipe. I have to shake it down, easy but I should not forget. Since i do not have an "inspection " access to the fire or the internals I have to fly blind till the hopper is low enough so that I can remove it and then partly disassemble the cover and peek over the fire.

J