Homemade boiler questions

Homemade boiler questions

PostBy: tigboy On: Thu Oct 30, 2008 8:36 pm

Hi everyone.I plan on building my 3rd prototype wood/coal boiler located in my attached garage.It currently is a pressurized system.I was wondering if a non-pressurized system with heat exchanger would be of any benefit ? I do not have domestic coil in presently, but have been considering.My stove would be comparable to a Harman SF 260 as far as design,however I was planning on 100 plus gals. capacity. My thinking was more is better as far as recovery time.(like a outdoor wood boiler).Does this sound feasible.Any advice??
tigboy
 
Stove/Furnace Make: Harman,Vermont Castings
Stove/Furnace Model: Mk III and Vigilant II

Re: Homemade boiler questions

PostBy: LsFarm On: Thu Oct 30, 2008 8:50 pm

Actually less is better for faster recovery.. more water is better for storing heat, but it takes longer to recover...

I don't see an advantage to building a non pressurized unit.. it just allows for evaporation and having to add fresh [oxygenated] water often,, and this only adds to corrosion issues..

A smaller water quantity with a fan forced combustion air setup will have faster recovery..

Greg L.
LsFarm
 
Stoker Coal Boiler: Axeman Anderson 260
Hand Fed Coal Boiler: Self-built 'Big Bertha' SS Boiler
Baseburners & Antiques: Keystone 11, Art Garland

Re: Homemade boiler questions

PostBy: tigboy On: Thu Oct 30, 2008 11:39 pm

I never got a chance to see a factory made handfired boiler up close. Do they use fan forced combustion? What exactly is that? My plan was to use natural draft,and try and control overfire using a aquastat that will dump excess heat through a zone valve bypass.I'd like to pick your brain more LsFarm,I understand less volume will recover faster.My last proto experiment worked kinda,when the zones called for heat, it drained the boiler from 190* to minus 150* in minutes.I figured that I had 27 gals.cap. in boiler. It took 20 mins. to recover before it would drain it again.What am I missing?
tigboy
 
Stove/Furnace Make: Harman,Vermont Castings
Stove/Furnace Model: Mk III and Vigilant II

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Re: Homemade boiler questions

PostBy: LsFarm On: Fri Oct 31, 2008 8:44 am

Hi tigboy, what you are 'missing' is that a draft-fired coal fire takes a while to ramp up the heat output.. If you have an aquastat that turns on a combustion fan that forces air through the ashpan area, up through the grates and the fire,, you will have only a minute or two before the fire ramps up to full heat.. not 10-15 minutes with natural draft..

An AHS multi-fuel boiler, or a Harman SF160-260-360 all have a combustion blower that is aquastat controled.. and usually a flapper that is temp controled to cover the inlet to the combustion fan as well.. this way the aquastat controls the air to the fire,, and the heat output..

I'm currently running an Axeman Anderson 260 boiler.. it has only about 30 gallons of water capacity.. even when all zones in the house call for heat at once, it will drop from 180* to 155* for about 5 minutes before recovering.. it has a very big fan forced turbulent draft and flame-to-waterjacket system.. the recovery rate is amazing..

Hope this helps.. Greg L

.
LsFarm
 
Stoker Coal Boiler: Axeman Anderson 260
Hand Fed Coal Boiler: Self-built 'Big Bertha' SS Boiler
Baseburners & Antiques: Keystone 11, Art Garland

Re: Homemade boiler questions

PostBy: coaledsweat On: Fri Oct 31, 2008 2:46 pm

I would say stick with a pressurized system, if nothing else, it will be cheaper.
100 gallons is way to much, 50 gallons in a hand fired and maybe 30 for a stoker max unless you are building a monster.
The forced draft is good for recovery as stated but does blow your heat up the chimney. If you are looking for some good natural draft controls, check the TARM, Burnham Woodlander and I think Energy King each have nice working natural draft control. You can find out about who makes the Burnahm draft regulator by PMing member Cheng_Baugh as he has a Woodlander. I believe it is the same control as was on my circa 1900 SEARS furnace I had back in the '80s. One thing is for sure, it won't wear out and will never fail when power is interrupted. :)
coaledsweat
 
Stoker Coal Boiler: Axeman Anderson 260M
Coal Size/Type: Pea

Re: Homemade boiler questions

PostBy: tigboy On: Fri Oct 31, 2008 7:18 pm

I was really stumped on the capacity issue ,but I think you guys are right on the money.After weighing the pro's and con's with a 100 plus cap.,I was considering 2-3" wide jackets on the sides and rear of stove. The top of the stove would hold the resevoir for a total of 50-60 gals. I was going to run smoke pipe straight thru top resevoir,surrounded by water. I have incorporated seven 1.5 " x3.0" rect tube above and across firebox,3.0" being vertical. Thanks for the info on the natural draft controls, I wanted to keep every thing simple and needed advice in this area. Any areas of this stove that I should be concerned about? I value your opinions (coaledsweat and LsFarm) on this matter.
Thanks Chuck
tigboy
 
Stove/Furnace Make: Harman,Vermont Castings
Stove/Furnace Model: Mk III and Vigilant II

Re: Homemade boiler questions

PostBy: coaledsweat On: Fri Oct 31, 2008 8:08 pm

A wet back? That is a good idea, it should improve efficiency, more heat in the water and less radiated to the room. Ideally, you want the return water to enter from the lowest point of the water jacket on each side.
The rectangular tubes, are they water filled or is it the smoke path? If it is the smoke path they will accumulate ash and require cleaning and probably frequently at that small size.

I got *censored* when I typed wet back as one word. :)
coaledsweat
 
Stoker Coal Boiler: Axeman Anderson 260M
Coal Size/Type: Pea

Re: Homemade boiler questions

PostBy: tigboy On: Sat Nov 01, 2008 11:41 pm

The rect. tubes are water filled with 1 " gap between then and 3"from top of stove.I wanted the fire to wrap through,around and above tubes to tranfere heat better.Does this sound right? My previous attempts just had water jackets on sides and top.Question, will the water in the tubes heat up and rise to top of resevoir without circulation pushing water through one side of tubes to the other. Could water just sit there and boil,or steam?? I would think that it would rise to top while cooler water took its place.Should water be circulating constantly in boiler? My friends stoker /boiler is set up like that.Any advice would help.
Thanks again Chuck
tigboy
 
Stove/Furnace Make: Harman,Vermont Castings
Stove/Furnace Model: Mk III and Vigilant II

Re: Homemade boiler questions

PostBy: LsFarm On: Sun Nov 02, 2008 1:05 am

Cut the ends of the square tubes at an angle. the water flowing up the sides will create a cross flow in the tubes.. Cut the angle to catch the water on one end , and direct the water up on the other.

Greg L.

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LsFarm
 
Stoker Coal Boiler: Axeman Anderson 260
Hand Fed Coal Boiler: Self-built 'Big Bertha' SS Boiler
Baseburners & Antiques: Keystone 11, Art Garland

Re: Homemade boiler questions

PostBy: tigboy On: Sun Nov 02, 2008 5:59 pm

LsFarm,are the ss bars on the side of the stove for support or serpentine flow? Just curious,what is the theory of operation with every other tube pointing up or down? Is the return water forced to enter from one side of the stove to the other,or does it enter from the bottom and allowed to surround stove.I believe a Harman 160-360 has its return enter from bottom of jacket,serpentine the sides to the back,through tubes across fire box,to top resevoir.I guess what I am wondering is if this is the way water needs to flow across the firebox,or will it flow on its own without being in a series circuit.By the look of the engineering on BB you must of had a theory on the most effective heat transfere. I would love to hear it if possible.
Thanks again Chuck
tigboy
 
Stove/Furnace Make: Harman,Vermont Castings
Stove/Furnace Model: Mk III and Vigilant II

Re: Homemade boiler questions

PostBy: LsFarm On: Mon Nov 03, 2008 1:14 pm

I designed the boiler to have water criss-cross through the tubes.. each tube that is slanted up on one end is slanted down on the other end.. the water 'weaves' it's way through the boiler.. absorbing as much heat as possible..

I'm not sure if a horizontal tube from left to right will circulate or not.. I didn't want to risk it, so I put in the angled cuts on the ends of the tubes.. it works.. when I first fire up the boiler, I can feel along the outside and feel the warm, cool, warm, cool, warm etc of the water circulation..

Greg L.
LsFarm
 
Stoker Coal Boiler: Axeman Anderson 260
Hand Fed Coal Boiler: Self-built 'Big Bertha' SS Boiler
Baseburners & Antiques: Keystone 11, Art Garland

Re: Homemade boiler questions

PostBy: tigboy On: Tue Nov 04, 2008 6:53 am

Some people suggested to have a circulation loop running constantly with a pump.I didn't think the water should be (forced),until the zones call for heat.Does this sound right? Does your stove circulate while recovering? I waqnted my stove to have kind of a thermal siphon effect,heated water rising,cooler water taking its place.Sound right???
Chuck
tigboy
 
Stove/Furnace Make: Harman,Vermont Castings
Stove/Furnace Model: Mk III and Vigilant II

Re: Homemade boiler questions

PostBy: LsFarm On: Tue Nov 04, 2008 10:45 am

My boiler and heating system runs a pump 24/7. I have weak glycol in the outdoor boiler, and a water/water heat exchanger to transfer the heat into the heat ahd DHW in my house and shop..

No, I don't think you should have stagnate water in a hand feed boiler,, there are too many hot spots that will boil. There are a lot of hand load boilers that do not circulate, but I prefer circulation.

Greg L.
LsFarm
 
Stoker Coal Boiler: Axeman Anderson 260
Hand Fed Coal Boiler: Self-built 'Big Bertha' SS Boiler
Baseburners & Antiques: Keystone 11, Art Garland

Re: Homemade boiler questions

PostBy: coaledsweat On: Tue Nov 04, 2008 7:03 pm

Even with the pump off, the water in your boiler will move on it's own internally. The water close to the firebox will get hotter and move to the top and the water at the top will be return to the bottom along the outside of the jacket. It will just keep cycling as the boiler builds temperature. It isn't going to happen in a rush though as water is an excellent medium to transfer heat so it is a very even process inside, you will not get a hot spot or start to boil in one corner if that is what you are thinking. Remember the system is under pressure and the temps need to go to about 260-280* before it will start to boil. You won't have water in one spot at 180 and in another at 260*+.
coaledsweat
 
Stoker Coal Boiler: Axeman Anderson 260M
Coal Size/Type: Pea

Re: Homemade boiler questions

PostBy: tigboy On: Wed Nov 05, 2008 12:28 am

Thanks for the info guys, I think I can go foward now with my design.I had an idea what was happening in the boiler ,but your info kept me from second guessing myself.I'm sure we will be talking again.
Thanks again
Chuck
tigboy
 
Stove/Furnace Make: Harman,Vermont Castings
Stove/Furnace Model: Mk III and Vigilant II

Visit Hitzer Stoves