School me! Furnace not working properly- What should I do?

School me! Furnace not working properly- What should I do?

PostBy: CoalisCoolxWarm On: Thu Oct 11, 2012 12:27 pm

Okay, time to start at the beginning. Apparently I need help on coal furnace designs and installs :)

First, some background.

I have a circa 1950's round firebrick lined combustion chamber with a circular grate around the perimeter and clamshell dumps in the center. The outer grate is now broken, but shakes mostly okay with the occasional poke at it and remove clunkers. The grate does stay in place but doesn't really rotate, but it does "bounce" which does okay.

It has a firebox approx 20” diameter, lined approx 20” high with firebrick, about 6” more to the exit flue and about 8” above that to a domed top.

The flue is 8” round to a VERY heavy kidney I built using the pattern from the old, burnt out one. I believe it is 14 gauge, with 10 or 12 gauge top and bottom pieces. Plasma cut and welded together. I didn’t want it to burn out 

The exit flue from the kidney is about 4” or so lower IIRC than the entrance flue and has a plate at the entrance flue (I think to divert the flow so it circulates in the kidney instead of just flowing straight through).

I have a very heavy walled steel exit pipe from this exit flue of the kidney welded in place to allow the shroud to cover everything. The pipe is about 8” long, then 90 deg up, about 4’ vertical black walled stove pipe with a cast iron manual damper, another 90 deg to horizontal, about 12” to clay thimble. Thimble is about 10” horizontal into chimney.

Chimney flue has a 17” x 17” chimney block so that would be 8” x 8” flue. I can’t get to roof right now, it is on 3rd story and I have to borrow a ladder for that. I estimated visually where the exposed one meets the brick at the top and measured, then called the place where I got the 3 block I added 2 yrs ago and got their sizes. Pretty sure it is correct.

My furnace is in basement, 7’ ceiling, below grade in the back. Chimney starts on grade and goes in a brick encased double chimney on outside of house (each chimney with its own blocks and liners, but sharing the brick outside) and extends 3 3/4 blocks above the peak of the roof. Chimney is basically centered on peak.

We have a VERY LARGE oak tree about 100 ft upwind from us. We are in a hollow and the tree is more than twice the height of our house.

I build a custom shroud out of 14 gauge steel to top of furnace, then added standard galvanized box for about 18” above that for ductwork. I used homemade Z seams to attach them. It is *mostly* airtight. I’d say leakage is in the single digit percentages.

It has a box on the side with its own enclosure for filters and blower motor sticking through a hole in the side of the shroud. A little air leaks out of the bottom where it meets the floor, but not much. It is a big old slow and steady blower the runs mostly full time once up to temp.

The furnace is steel. I rescued and refurbished it a few years back, even painting it with high temp black paint after sandblasting.

The loading door is rectangular and steel with a steel baffle on the inside covering the door slide vents.

The ash door is large rectangular with a flap style damper. I believe it is setup for an auto-damper motor, which I have, but I’ve never used or setup yet. I haven’t been happy with its performance yet, so not ready to automate. Maybe that is backaswards???

Now the problems.

Although it puts out a LOT of heat, it seems like I always have to have a nearly full firebox to get good heat and keep shaking and stoking it to get a hot, effective burn. A small fire just doesn’t make much heat or last very long.

When I can get it banked nicely, it likes to get crusty and hollow out by burning all the coal under/inside the crust. Trouble is, when we poke it down there may not be enough hot coals to load it back up without a few intermediate loads and checks to build up the bed of hot coals.

This all makes for a fire that needs nearly constant attention. It heats, but overnight is a bear. I have to start a few hours before bed and fire it hot to get hot coals and bed it over. Late night and early morning, else the fire will burn out. It is usually quite cool in the am and we have to stoke it with wood to get it fired up again. Not rebuild, but definitely build it up.

If I cut it down too far, it drops temp and starts to smoke instead of putting out heat. No smoke in house, except when fixing the fire and forgetting to open the stove pipe damper first ;)

We get a LOT of ashes. About 3 5-gallon buckets in 2 days.

These are worst case. Not always that bad, especially if I have it HOT, but then it uses a lot of coal. But these scenarios do happen about half the time- enough to classify it as a problem.

I have a few possibilities and am looking for some input?

1. Chimney changes. Extend chimney, reduce it with a liner, add barometric damper
2. Seal up ash pan door and shaker rod holes and add a fan to ash door using pipe to direct air and protect fan.
3. Seal up loading door
4. Reduce flue sizes on furnace and/or kidney.
5. Some sort of auto controls?
6. Line more of firebox with firebrick. Current firebrick are in poor to fair condition and it is HARD to find curved, so likely going to be doing some 15 sided polygon or something soon anyways ;)
7. Add internal deflector plate or baffle of some kind inside firebox- welded or suspended?
8. Add baffles or air channels or magic pixie dust to firebox?
9. Change coal to other size, heat range, or hard coal?

I have access to a manometer (borrow) but don’t know what its value should be.

I am using nut sized soft coal from local source in Western PA. Tried some “hotter” coal, but it was harder to light and that seems to be something we do (build it back up) quite often.

Oh, our house is just under 4000 sq ft and half of it is semi-remodeled and well insulated while the other half is not and poorly insulated.

When fixing the fire and the chimney is smoking, the smoke goes out the chimney and often rolls down the roof and side of chimney, leaving very light soot. I have about 2-3 inches of soot in cleanout from last season.

I can build and fabricate most things. Have access to plasma cutter, torches, MIG, grinders, etc. Just don’t know *what* to change???

I am obviously missing something! Please help me understand *what* it is I need to modify and tame this beast. We love the hot air and the way it heats, but not being a slave to it. Funds are limited, but “heat” is not an option :)

Sorry so long, trying to be complete.

Thanks!

- JC
CoalisCoolxWarm
 
Stoker Coal Boiler: Keystoker KA6
Hand Fed Coal Furnace: old Sears rebuilt, bituminous
Coal Size/Type: Kittanning Seam, Stove size
Stove/Furnace Make: old handfired bituminous

Re: School me! Furnace not working properly- What should I do?

PostBy: rockwood On: Thu Oct 11, 2012 2:05 pm

How 'bout finding an underfeed stoker to interface with your furnace?

Look at these photos....scroll down and you will see the furnace which is similar to your design but without ductwork.

http://www.dapcom.com/hamfriends/ko7r09.htm
rockwood
 
Hot Air Coal Stoker Furnace: Stokermatic coal furnace
Hand Fed Coal Stove: Rockwood Stoveworks Circulator
Baseburners & Antiques: Malleable/Monarch Range
Coal Size/Type: Soft coal: Lump and stoker (slack coal)

Re: School me! Furnace not working properly- What should I do?

PostBy: Pacowy On: Thu Oct 11, 2012 2:28 pm

Please check your private messages (envelope icon at top of page).

Mike
Pacowy
 
Stoker Coal Boiler: H.B. Smith 350 Mills boiler/EFM 85R stoker
Coal Size/Type: Buckwheat/anthracite

Visit Hitzer Stoves

Re: School me! Furnace not working properly- What should I do?

PostBy: CoalisCoolxWarm On: Thu Oct 11, 2012 3:36 pm

That furnace in the link does look very similar to mine without the shroud.

What is an underfeed? Are you running oil/waste in that furnace as a pot furnace?

I also checked pm and will get back to you shortly, thanks.

Any other input about tweaking my setup?
CoalisCoolxWarm
 
Stoker Coal Boiler: Keystoker KA6
Hand Fed Coal Furnace: old Sears rebuilt, bituminous
Coal Size/Type: Kittanning Seam, Stove size
Stove/Furnace Make: old handfired bituminous

Re: School me! Furnace not working properly- What should I do?

PostBy: CoalisCoolxWarm On: Thu Oct 11, 2012 3:42 pm

That furnace in the link does look very similar to mine without the shroud.

What is an underfeed? Are you running oil/waste in that furnace as a pot furnace?

I also checked pm and will get back to you shortly, thanks.

Any other input about tweaking my setup?
CoalisCoolxWarm
 
Stoker Coal Boiler: Keystoker KA6
Hand Fed Coal Furnace: old Sears rebuilt, bituminous
Coal Size/Type: Kittanning Seam, Stove size
Stove/Furnace Make: old handfired bituminous

Re: School me! Furnace not working properly- What should I do?

PostBy: Rob R. On: Thu Oct 11, 2012 3:49 pm

After reading your post, it sounds like the characteristics of the coal make it a poor choice for hand-firing. It also sounds like the heating load of your home is quite high.
Rob R.
 
Stoker Coal Boiler: EFM DF520
Hand Fed Coal Stove: Hitzer 50-93
Coal Size/Type: Lehigh Rice
Other Heating: Dad's 1953 EFM Highboy

Re: School me! Furnace not working properly- What should I do?

PostBy: Pacowy On: Thu Oct 11, 2012 3:50 pm

An underfeed stoker feeds coal and air into the underside of a burn pot. An underfeed conversion stoker (see example in pic) is normally intended to slide into the bottom/ash door of a furnace or boiler. They vary widely in size and output capability.

Mike
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Pacowy
 
Stoker Coal Boiler: H.B. Smith 350 Mills boiler/EFM 85R stoker
Coal Size/Type: Buckwheat/anthracite

Re: School me! Furnace not working properly- What should I do?

PostBy: rockwood On: Thu Oct 11, 2012 4:02 pm

Other replies happened before I was able to submit this post so sorry if some of it is redundant ;)


In the first of the three photo's of the furnace in that link I posted shows the stoker (rusty green device with lid/door on top sitting in front of the furnace).
An underfeed stoker is an electromechanical device that feeds coal into the furnace automatically when a controlling thermostat calls for heat.
Here is a cutaway diagram of a underfeed coal stoker connected to a boiler.

http://www.google.com/imgres?imgurl=htt ... wAg&dur=45

You dump stoker coal (this coal is approx. 1 inch and smaller) into the hopper and an auger (worm/feedscrew) at the bottom of the hopper moves the coal through a tube that leads to a pot (retort bowl) at the bottom of the firebox where the coal burns with intense heat due to a forced draft fan (located in the stoker unit). There are holes in the firepot (called tuyeres) to supply air to the fire. Because the fire burns so intensely, clinkers are created that should be removed daily...also, there is very little smoke from burning bituminous coal when using underfeed stokers because fresh coal is being pushed into the fire from underneath so almost all the volatile matter in the coal is consumed.
rockwood
 
Hot Air Coal Stoker Furnace: Stokermatic coal furnace
Hand Fed Coal Stove: Rockwood Stoveworks Circulator
Baseburners & Antiques: Malleable/Monarch Range
Coal Size/Type: Soft coal: Lump and stoker (slack coal)

Re: School me! Furnace not working properly- What should I do?

PostBy: CoalisCoolxWarm On: Thu Oct 11, 2012 4:16 pm

Underfeed looks very interesting! By removing clinkers daily...reaching into firebox or some other way?

@ Rob R- Are you saying I should use a different size coal?

How much does a typical underfeed addon run? I am familiar with auger feed keystoker anthracite from about 25 yrs ago in a boiler, but underfeed is new to me.

Update: I just made a call. The stainless steel auger is still around and in good shape.

I'm picturing the underfeed as an on-demand, self-feeding setup that would require filling a hopper and emptying ashes and doing something with clinkers.

I haven't bought more coal this season yet, so it's easy to change size/type/supplier. Still have some from last season.

Also- what about my flue size/height and such...is it okay?

Thanks. All good info so far. I've been reading quite a while, but it's time to jump in and ask for some help ;) I do appreciate it!
CoalisCoolxWarm
 
Stoker Coal Boiler: Keystoker KA6
Hand Fed Coal Furnace: old Sears rebuilt, bituminous
Coal Size/Type: Kittanning Seam, Stove size
Stove/Furnace Make: old handfired bituminous

Re: School me! Furnace not working properly- What should I do?

PostBy: rockwood On: Thu Oct 11, 2012 4:27 pm

CoalisCoolxWarm wrote:I'm picturing the underfeed as an on-demand, self-feeding setup that would require filling a hopper and emptying ashes and doing something with clinkers.

You got it!...In days gone by you were considered "uptown" if you had a mechanical stoker instead of having to fire the furnace by hand.

Clinkers are best removed using tongs but it can be done with a typical fireplace poker or an ash shovel.

Depending on where you are located, used underfeed stokers can still be found.
rockwood
 
Hot Air Coal Stoker Furnace: Stokermatic coal furnace
Hand Fed Coal Stove: Rockwood Stoveworks Circulator
Baseburners & Antiques: Malleable/Monarch Range
Coal Size/Type: Soft coal: Lump and stoker (slack coal)

Re: School me! Furnace not working properly- What should I do?

PostBy: Berlin On: Fri Oct 12, 2012 12:29 am

an underfeed stoker is an excellent choice, but I think the problem you're having with you appliance now starts with the coal. You need a DEEP bed of coal, good coal, and large size. In western Pa try to get some pittsburgh lump or try valier coalyards "oversize" coal. The swelling and crusting over is a sign of a high coke button which makes hand firing coal as bad as you've discovered. It may well be that the draft is not adequate or that your setup needs some changes, but, start by changing a definite problem - your coal.
Berlin
 
Hot Air Coal Stoker Furnace: Will-Burt Combustioneer 77B
Coal Size/Type: Ohio BITUMINOUS pea stoker coal

Re: School me! Furnace not working properly- What should I do?

PostBy: CoalisCoolxWarm On: Fri Oct 12, 2012 10:12 am

Berlin wrote:an underfeed stoker is an excellent choice, but I think the problem you're having with you appliance now starts with the coal. You need a DEEP bed of coal, good coal, and large size. In western Pa try to get some pittsburgh lump or try valier coalyards "oversize" coal. The swelling and crusting over is a sign of a high coke button which makes hand firing coal as bad as you've discovered. It may well be that the draft is not adequate or that your setup needs some changes, but, start by changing a definite problem - your coal.


I never considered the coke being an issue, but it makes sense. What size do you suggest? I have been getting it from Mill Creek in Seward, PA. Actually it was the high rock content that jammed my grates and caused the breakage. Pieces of shale in the coal.

I had some 'hotter' coal before I added 3 blocks to the chimney and had trouble lighting it. Probably would be fine now ;-)

Fired it up last night and it worked great. We really do like the heat it gives. I'm thinking if I had a way to open the flue damper when the fire gets low, it would be a major improvement between hot and cooling fires?

A baro and draft automated systems wouldn't hold the heat like the manual damper does. When the fire is hot, I close the damper almost all the way, open lower draft damper about half, open feed door vent about half, and she makes heat like mad with a beautiful fire.

But we can't sustain it. Either we load coal on the burning coals and set it back but will keep it lit, or we wait and when it burns down it may give us trouble stoking and building back up.
CoalisCoolxWarm
 
Stoker Coal Boiler: Keystoker KA6
Hand Fed Coal Furnace: old Sears rebuilt, bituminous
Coal Size/Type: Kittanning Seam, Stove size
Stove/Furnace Make: old handfired bituminous

Re: School me! Furnace not working properly- What should I do?

PostBy: CoalisCoolxWarm On: Sat Oct 26, 2013 12:42 pm

Update: Oct 2013

I have replaced the broken round grate. Myers Supply in Johnstown,, PA is my 'go to guy' for old cast iron parts. I post this to help others, but don't take the parts I need ;) According to Mark (yes, his name is really Mark Meyers!) I have a 17" Sears grate/stove. Sounds about right. I showed him a pic of the stove and he seems convinced, so I won't argue.

Went in the back parts room and found the right grate by matching up the features. Then found out there is a number on the grate that would have saved time...duh! Cost is $128-$158, depending on what you get. I don't know what others may cost. It was about double what I found on Craigs List, but nobody returned my emails (pay attention if you are advertising on CL).

I replaced the stove pipe this year (2 yrs on the last set, I didn't clean it last year). A few points on this.

1. You ASOLUTELY should clean your pipe, kidney, and furnace each year. I have some medical issues, but should have called a friend last year instead of skipping it.

2. Lower section had a longer piece of straight pipe (all 8"), then elbow, straight with MPD, then elbow at top and another straight piece.

3. Lower elbow/pipe was about 1/3-1/2 filled with ash! Kidney had about 10" of ash in it, near the exit pipe. I vacuumed it all out. I need to work out a better vacuum system next time. Shop vac hates this stuff.

4. When I rebuilt the stove a few years back and fabricated a new kidney, I made some mistakes. Learn from mine. A) You should not use the heaviest gauge you have for it. Thicker lasts longer, but heat transfer suffers. B) Exit pipes should slope 1/4" per foot. I only found this recently, but makes sense- like plumbing but in reverse.

5. I used a very short piece of straight pipe from the back of the stove, at the bottom of the kidney. 4" inside the exit pipe (at least 1/4", I'm okay with that, 8" ID EXACTLY) and about 1.5-2" sticking out. ATTACH ELBOW HERE! Start the pipe upward direction as soon as possible from the back of the stove.

6. About 10" of straight pipe from the elbow and contains the MPD. I use the very heavy tin snips from Harbor Freight to cut my pipe. I've used tin snips, grinders, saws all, and about everything else in the past. The giant angles about 10" long set works great. Un-roll pipe as you cut. Make a matching cut from the opposite side as far as they will go until they jam. The 'un rigid' (no ridge, if you know what I mean) side should be to the LEFT for your main cuts. It unrolls well, where the ridged side will hold its shape and refuse to unroll. Get that? Read it again, it will make your life much better ;)

7. Next is a Tee for the Barometric damper. Get a FULL SIZED damper, meaning match the diameter of your stove pipe. 8" pipe means 8" baro. Again, Meyers had all this. Not always the cheapest, but fair and QUALITY. 24 gauge black pipe (call ahead, this is a limited stock item in 8" and gets bought up all the time). This pipe is MUCH BETTER than the stuff I got from a local hw store before, which is the same or a bit better than big box stores. Make sure your baro is level left to right. This is a RC calibrated version.

8. Next is another 90* elbow. I used all my vertical (not used by the tee) for the MPD section.

9. I used about 18" or so exposed horizontal pipe (Sorry, don't remember exactly) into the clay thimble. The pipe is a fair amount smaller, leaving gaps and the ability to SLOPE IT UPWARDS at least 1/4" per foot.

10. Start at the bottom with a helper to hold it all in place and put in your screws in each joint. Adjust it as you like, then use RUTLAND FURNACE CEMENT in the cartridge/tube. Home Depot carries it, but Tractor Supply is $.50 less per tube, when they have it. Call ahead, this is hard to locate instock. BTW, HD with price match TSC, being a 'sister store' I used the furnace cement to fill in all the gaps and then seal each joint. I work it with 2 fingers into every gap in the seams. Give it a half hour or so before trying to remove from your fingers and you'll keep the skin.

11. 1 hr or so for the cement to cure, then heat with newspaper and then small pieces of very dry wood for a slow ramp up to temp to cure both the stove pipe paint and the furnace cement.

12. I also cleaned out the chimney cleanout, THAT I THOUGHT WAS CLEAN, using a very small shovel. The cleanout door was clear, but by sticking in the shovel I ended up removing about 2/3 of a bucket of stickey black junk from the chimney. I used the furnace cement to seal the door closed. It is easy to remove when necessary using a hammer to tap it gently.

13. Note about the furnace cement. Do NOT use DAP. Google for the reasons. Do NOT use the tan or grey 'fireplace mortar' from any vendor. Only use the BLACK FURNACE CEMENT as it will stick steel to masonry, steel to steel, masonry to masonry, etc. About $3 /tube, I used 1 full tube, patching everywhere I thought I should. I will use another tube to stick additional row of firebrick in the furnace itself.

14. Start with Baro at .06 as marked, per the baro instructions. I don't know if I can lower this, but I think so. More on this later.

15. I also had to fabricate a new roller holder and remove the old rivets and pieces from the stove. Welder, torches, grinder, etc. Fun, but worth it. You would be AMAZED at how easily bolts/nuts are removed after a few years in the heat. I used stainless when I rebuilt it a few yrs back and am glad I did.



16.
Last edited by CoalisCoolxWarm on Sat Oct 26, 2013 1:06 pm, edited 1 time in total.
CoalisCoolxWarm
 
Stoker Coal Boiler: Keystoker KA6
Hand Fed Coal Furnace: old Sears rebuilt, bituminous
Coal Size/Type: Kittanning Seam, Stove size
Stove/Furnace Make: old handfired bituminous

Re: School me! Furnace not working properly- What should I do?

PostBy: CoalisCoolxWarm On: Sat Oct 26, 2013 12:52 pm

I am using the same Valier stove bituminous as last season. I may try nut soon as things are really getting more stable. It's amazing how much the baro is moving and how many gusts we have here with all the trees and such.

My air chamber is staying about 120F, moving only occasionally, far less than last year, 180F to 100F wasn't uncommon in an hour or so. The fire seems to be lasting better. And we burnt it from Wed about 9pm to Saturday am on only had ONE BUCKET OF ASH!

Other years this would have been at least a bucket a day.

I do wish we could have our air closer to 150F, though. But it just doesn't seem to want to be there. It feels like it 'wants' to be at 120F. I don't have a thermometer on the fire itself or the pipes, so no idea what they are.

I can tell you our house has been at 52F a couple days the past week or so before the furnace and 2 days after getting it going, it is 67-70F . Last year it was ALWAYS 50-60F in the am when I got up, even though I would bank the fire about 1am.

This am with 36F outside, the house as 67F, from 1030pm and nothing done until 830am. I added coal at night, but didn't 'bank' it and cut it way back, just let it go.

Hopefully this is the sign of things to come. We just brought in 1.05 tons of coal yesterday, so we'll see what the consumption is long term.

I'd really like some input on the draft setting for the baro. That may be where I am losing some heat?

I am not an expert, but thought this may help some others. Learn from my mistakes and offer some tips if you have them!
CoalisCoolxWarm
 
Stoker Coal Boiler: Keystoker KA6
Hand Fed Coal Furnace: old Sears rebuilt, bituminous
Coal Size/Type: Kittanning Seam, Stove size
Stove/Furnace Make: old handfired bituminous

Re: School me! Furnace not working properly- What should I do?

PostBy: lsayre On: Sat Oct 26, 2013 1:20 pm

Having your barometric damper open at 0.06" is OK for if you don't have a manometer installed with which to monitor your actual draft. The factory setting of 0.06" is only approximate. With a manometer you can take it down to where it just begins to break open at an honest (as in measured) 0.04".
lsayre
 
Stoker Coal Boiler: AHS S130 Coal Gun
Coal Size/Type: Stockton Anthracite Pea
Other Heating: Resistance Boiler (13.5 KW)

Visit Hitzer Stoves