My homemade outdoor wood furnace (boiler)

[stee6043]

Awesome thread. Thanks for sharing!

 

[Lapeer20m]

I had an epiphany this morning when it comes to automatic draft control....I considered using some crazy Rube Goldberg mechanism crafted from junk I have laying around, but I want something simple and reliable.

Unless someone talks me out of it I think I'm gonna use a series of 1 inch solenoid sprinkler valves. However many it takes to equal the area of my current draft control. 3 inches.

I'll have to take steps to keep them from getting too warm.

I could even control half of them at a time when I don't need to make as much heat.

What do u guys think?

 

[stayfitz]

I want to be you when I grow up! Absolutely amazing work! Thank you very much for sharing!

 

[Lapeer20m]

I talked myself out of solenoid valves. Not because its not a good idea, but because its too expensive.

I did the math: Pi r2 indicates that I would need almost 10 one inch solenoid valves. At almost $13 each plus the cost of plumbing fittings it is cost prohibitive.

Home Depot sells a 6" auto damper for $59.

To be continued....

 

[Lapeer20m]

here are photos....

Here is the spot where the lines run into the house. In this photo, you can see the naked red pex lines, and a pair of lines that have armorflex insulation over the pex.

Here is the culvert that the lines are running through......

I started insulating the boiler with R-30 insulation.

The entire boiler will be built into a "cabinet" which will be inside an 8x8 shed.

Here is the heat exchanger just prior to installation:

I'm sure the installation process is not as pretty as some of the other members, but it'll do. I only had to go back and fix one leak.

For the automated draft control, I found this awesome 24vac actuator. It has built in limit switch so you can leave power to it all the time. This takes a lot of complexity out of trying to manufacture your own control. I paid less than $7 for it. I may also add a damper control in the future. I actually picked up three of these handy little gizmo's.

I still have a lot to do, but it is operational right now. Low temperature outside this morning was 32 degrees F but it was nice and toasty in the house.

 

[Jags]

Pretty neat build. I think you are doing a fine job for a 100% DIY. It will be interesting to hear the wood consumption of this beast when we get deep into heating season.

 

[saladdin]

I thought I was a DIY'er. If you are calling yourself "only" a DIY'er then I'm demoting myself to village idiot because we're not in the same league.

Please keep the updates coming.

 

[Lapeer20m]

here is my draft control version 1.0. I may go back and make a more heavy duty flapper door. This one is made from a paint can lid with a spring loaded hinge. The actuator from the above post will open/close this little door.

first i want to finish insulating and building the shed. Then i need to figure out all of the logic circuits: I think i have most of it worked out in my head.....

I need the lpg boiler in the house to fire when there is no heat available from the owb,

The draft control needs to close at 190? and reopen at 160-170?

I also want built in freeze protection, so if the owb temperature drops to perhaps 35 or 40 degrees the lpg boiler will heat the water in the owb. I don't want to waste propane, but a little propane is a lot cheaper and easier than allowing the owb to freeze. It's too bad that i can't find a simple way to install a 60 watt light bulb or a toaster oven element inside the burn chamber. I'm sure this would be enough to keep things from freezing.

since the boiler will be insulated to a value of at least R-50, plus it'll be inside of a shed that will eventually also be insulated, the risk of freezing should be minimal. We don't usually get too many days down in the single digits. Perhaps simply circulating water through the heat exchanger in the house even without lpg being used will keep things from freezing. We may leave home for a couple of days at a time on great occasion, which is about the only time freezing should be a concern.

 

[Jags]

Why not use a 110V 1500W water heater element? You would obviously need a control thermostat on it, but it could be integrated right into the system.

 

[Lapeer20m]

Why not use a 110V 1500W water heater element? You would obviously need a control thermostat on it, but it could be integrated right into the system.

That's genius! I could just drill and tap a hole in the back of the water jacket. And most importantly, it should be feliable because its very simple.

Thanks for the suggestion!

 

[Jags]

I think they are standard thread. Weld the appropriate pipe coupler onto the water jacket and carry on.

 

[maple1]

McGyver in da house!



On the freeze thing, could you just run the circulator 24/7? Then when the LP boiler sees cold water it'll just do it's own thing. I'm not fussy about running a circ 24/7, but lots of people do it.

 

[BoilerMan]

If you run a water heater element, you can simply supply it with 120V instead of the rated 240V and half the wattage. Get a cheap 3500W element and it becomes a 1750W. Plenty to keep your boiler from freezing and you can feed it with a 12-2 piece of UF buried to the boiler.

TS

 

[ewdudley]

If you run a water heater element, you can simply supply it with 120V instead of the rated 240V and half the wattage. Get a cheap 3500W element and it becomes a 1750W. ...

(Whoops, probably not what you meant since wattage varies as square of voltage, so 1/2 the voltage yields 1/4 the wattage, or 875 watts in the example.)

 

[BoilerMan]

You are correct, and to think I work with it everyday. I was thinking amperage.

TS

 

[Lapeer20m]

I feel privileged to tap into such a vast knowledge base here on this forum.

 

[Fred61]

how many watts do you think are needed? You're talking much higher numbers than the original 60 watt bulb contemplated above.

 

[Lapeer20m]

how many watts do you think are needed? You're talking much higher numbers than the original 60 watt bulb contemplated above.

It's not as if I did any scientific calculation. 800 watts, while approximately 8x the power consumption of the light bulb should do a fine job and would likely use the same amount of energy to raise the temperature of the water above 40 degrees but it would add more btu's in less time.

 

[Fred61]

I was just thinking about the economic side. I would want the lowest wattage that would do the job but it would be difficult to calculate the wattage needed given all the variables. I was rummaging through my junk (treasures) last week and found a McMaster Carr bag with 4 heaters in it that I had purchased years ago for some experimental project. Two were built like hose clamps that would fit 3/4 inch copper and 2 were tiny rods that would go into a dry well quite nicely. I don't recall the wattage but memory tells me they were at least 100 watts.

Installing something like that and moving the water would hold off jack frost quite nicely, I would think.

 

[maple1]

If you just ran the circ all the time, it should pick up heat from the HX when the fire is out & LP is doing backup duty. Right?

 

[Lapeer20m]

I am not sold on running the circulator 24x7. Plus, I don't want the lp boiler to heat the owb on a regular basis, and with my current setup that's what would happen if the owb circulator was running while the lp boiler was in operation.

I really like the simplicity of a water heater element and thermostat, assuming the tstat has an anti freeze setting. It's cheap, reliable, simple, and effective.

Efficiency is not top of the list for anti-freeze technology. It may never actually be utilized and it only has to keep the water above freezing. The difference in efficiency between a 100 watt element heating 900 pounds of water 3 degrees vs an 800 watt element is likely negligible. And all the parts for the 800 watt setup is redily available from Home Depot.

I appreciate everyone's opinion and input.

 

[maple1]

What about just running the circ when the boiler goes cold, or it's a certain point below freezing outside? Or you could just manually turn it on with a switch if you'll be away for a while.

Just thinking with a circ already in place, and the OWB already attached to a backup heat source in the house - everything basically is already there for freeze protection, no plumbing mods or opening of the system needed. Plus a circ pump draws a lot less electricity than a heating element.

 

[mchasal]

I am not sold on running the circulator 24x7. Plus, I don't want the lp boiler to heat the owb on a regular basis, and with my current setup that's what would happen if the owb circulator was running while the lp boiler was in operation.

I really like the simplicity of a water heater element and thermostat, assuming the tstat has an anti freeze setting. It's cheap, reliable, simple, and effective.

Efficiency is not top of the list for anti-freeze technology. It may never actually be utilized and it only has to keep the water above freezing. The difference in efficiency between a 100 watt element heating 900 pounds of water 3 degrees vs an 800 watt element is likely negligible. And all the parts for the 800 watt setup is redily available from Home Depot.

I appreciate everyone's opinion and input.

Even with heating element(s) in the boiler, without a circ running won't you still have an issue with the outdoor lines freezing up? Or do you expect to get enough natural cycling to curb that?

As an off the wall idea, for truly emergency protection, you could tee in a zone valve to one of the lines hooked to a thermostat that would just dump the water if it's getting close to freezing. Water's pretty easy to replace

 

[Jags]

As an off the wall idea, for truly emergency protection, you could tee in a zone valve to one of the lines hooked to a thermostat that would just dump the water if it's getting close to freezing. Water's pretty easy to replace

That is a neat idea - not sure how practical for this application, but I like it. Way to think outside of the box.

 

[Lapeer20m]

Even with heating element(s) in the boiler, without a circ running won't you still have an issue with the outdoor lines freezing up? Or do you expect to get enough natural cycling to curb that?

As an off the wall idea, for truly emergency protection, you could tee in a zone valve to one of the lines hooked to a thermostat that would just dump the water if it's getting close to freezing. Water's pretty easy to replace

That is an interesting idea also......and cheap, easy, reliable.