I'm building a homemade boiler

Yeah you will figure it out, just a little learning curve. I would suggest keeping the temps up though once you start burning. Since you are using a higher efficiency design then most conventional boilers you are going to be more susceptible to lower temps causing moisture. When I burned softwood it was always more of a pain than it was worth.

You will get it figured out pretty quick. Its mostly about getting a decent coal bed going, once that happens things will work pretty smooth. I found with my old stove that I would always place a piece off to the side away from being directly blown on by the blower which kept me a nice area of coals that if I let the stove run down to nothing I could rake it over and use that to light the next load. I also put a second Ranco aquastat which I used to break power to the blower motor and flapper on the boiler if my water temp dropped below 165. I ran my boiler 170 on 180 off. If the boiler dropped to 165 it meant I was out of wood, so the aquastat would kill the fan and flapper and leave me a nice big bed of coals instead of burning the coal bed up. It worked out really really well.

Quick math to raise your boiler from 140deg to 180deg, 120gal x 8.43lbs x 40deg= 40,464btu/6050btu/lb of wood = 6.6 lbs wood. Possibly in moderate weather with low load, your wood does not have much of a chance of a consistent burn to generate a reliable coal bed, as inferred above. Softwood unless you can match your load [ throw a few pieces of lumber scrap in while you are under full load] won't give you a reliable coal bed, as above with what you currently have, hardwood would be much better. Hopefully cold weather will generate more frequent cycling reducing the problem. With moderate storage and weighed wood loads all your efforts will shine! Your craftsmanship is flawless.

Just a couple quick points. Your 6600 Btu is based upon 100 percent combustion efficiency of the stove. The boiler is probably around 50 perfect efficient. Also does anyone really weigh their wood?

hondaracer2oo4 said:

Also does anyone really weigh their wood?

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Yes, there are some here that do...

Honda, the wood btu value does not change, the boiler combustion and system effiency determine how much wood you will need at a given moisture content. Here are some examples from my records, start water temp=141.5, end temp=174.2, delta of 23.7deg with 100lbs wood= 3.05lbs/deg raised. My boiler 1906 gallons= 15896btu/deg raised, or 5211btu extracted out of the 6550 available= 86.1% effiency, for this particular burn.
Yes i weigh my wood.

Yes I understand that the BTU's available in 1 pound of wood does not change based upon the efficiency of the particular unit. My point was that he stated that he would need 6.6 pounds of wood to raise the temp the desired amount which is not the case since the unit is probably 50% efficient at moving the available btus from the wood to the water which would mean that he would need twice that weight of wood to raise the water the desired amount.

warno said:

I did have that though about a second aquastat to cut power at a lower water temp. I may still do that. But my question with that is how do you bypass it to get things going again with a new load of wood?

Thanks for the numbers on my BTUs. I don't know the math but I do know this things heats water extremely fast. Recovery time is pretty much minutes.

We are having high 50s today so I dropped my differintial down to 3 degrees in hopes to keep it going. I worked in the garage for about 3 hours this morning and the blower in the garage only kicked on one time, and that was after I opened the drive in door.

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on mine I added a low temp aquastat but I used it to cut off my circulator pump and heat exchanger fan. figuring if my temp got low in the boiler I didn't want it to keep sucking heat away from it. without it if the boiler fell behind on really cold days (below zero) the loop would just keep sucking it down and the air would come out of registers luke warm.

on a side note I started out with a forced combustion blower. had a hard time with keeping coals overnights on real cold nights. around year 7 or 8 my blower died and I cut it off and welded on a gravity closed door with a solenoid to pull it open and was much happier with it. not sure if it would work in your application with the long section of horizontal heat exchanger and the bends might not have enough natural draft. but my old boss signifigantly reduced his wood usage and burn times on his old aquatherm by adding a speed control to his fan. he was a cheapskate and used a dimmer switch. I would have used something like this. http://www.harborfreight.com/router-speed-control-43060.html .. hey for 20 bucks try it in a few different speeds and if it doesn't help your only out 20 bucks.

I used a homemade owb for about 15 years. but with my new house with virtually no land and right on the edge of town so this year I switched to a regular wood stove. with room to stack a months worth of wood easily on the enclosed front porch, about 1/2 a face cord in the back room 12 feet or so away. I loved my boiler but the going out in the snow 2 or 3 times a day to fill it I wont miss.

My point is that even if you put 25lbs wood in the boiler, your hard pressed to find enough coals left for a relight. Relight time with 120 gallons can become a challenge, cold weather you could go through your load faster than thought=no coals or shoulder seasons idiling for prolonged times =no coals. The aquastat differential time changes might help, but keeping the combustion air inlet slightly open with 120 gallons could overheat. My long term thought would be to calculate what a 12 hr btu load would be and add storage.

Yes sometimes you will misjudge the amount needed untill the next fill on those cold days. My old boiler was 120 gallons though and my firebox was 20 cu ft, not sure how big your firebox is? The way that I had my low temp aquastat set up was I brought power into both the aquastat and a bathroom timer switch. Out of the aquastat and timer I ran the power to the blower motor and soleniod. If the aquastat cut the power to the blower and soleniod because the water temp dropped I would go and press 1 hour on the bathroom timer which would power the fan and soleniod for 1 hour. By the 1 hour mark the water temp will rise above the cut in on the low temp aquastat and it will continue th power after te bathroom timer kicks off.

Holy crap. That's 1/4 cord.

Mine's like 3 cu.ft.

nature of the beast when your firebox is surrounded by water. especially when your coming back on after an up to temp smoldering cycle. the pine might help bring the combustion chamber temp up a little faster shortening the "freight train" smoke. but mix to much in and it will shorten your burn time and make less coals.

I second notshubby, do you have time to build your storage now, it will help alot with both your prior posts, hows your seasoned wood supply?

warno said:

I hate to admit it but right now I'm "that guy" since I've been trying to get this thing leaving me some coals I've been burning my hedge pieces. The pic isn't real clear but this is what I've got this going on now. It's a pretty dense smoke coming from the chimney. I'm also wondering if I should put on another section of chimney to get the smoke up higher. What do you guys think?

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When I was burning the pine lumber pieces it was only little whisps of smoke. I know these types of boilers smoke but if I start mixing my pine lumber in with my hedge do you guys think it will help cut down on my smoking problem?

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Are you sure that is all smoke? Might be some steam in there?

This is kind of a catch-22 time of year for an OWB. Heat load isn't that high so if you try to put enough wood in to last the hours you want for a re-load, it will smolder a lot & condense creosote in the firebox, then when you load up again it will burn that creosote off & make smoke. Might have to just load for the heat you want until you come back, and plan on having to relight a new fire when you do come back.

Most all of us indoor boiler guys make a new fire every day - so not having hot coals to load on is a given. For me anyway.

Don't get discouraged its a learning thing. Like I said before, the softwood and scrap is a pain to burn, leaves no coals, burns fast and appears like you have enough wood to last 12 hours but it never is. Something that will also help you to keep a coal bed is to cover a piece of your grates so that the blower can't directly blow on th coals and kill your coal bed.