Homemade OWB Questions

[Turkeyslayer]

So I bought a homemade OWB from a neighbour and and am in the process of aquiring parts and pieces to hook it up. The boiler is made out of a 1000 gallon propane tank cut in half with a firebox welded into the front. The chimney is made out of well casing and runs out of the top of the stove horizontally through the water tank, then does a 90 up then another 90 to horizontal, then to the front of the boiler where it 90's up and out. I was told it holds approx 450 gallons of water in the tank.

We will be heating our house which is approx 2500 sq ft. The house is a big old poorly insulated farm house with crappy windows. We have a forced air furnace in the basement which I plan on putting a rad into. I would also like to heat my DHW with this unit.

Now I would like to find out many things including: What size of pump should I be running. What type of rad for the furnace. Heat exchanger or sidearm for the DHW. Temp settings for the boiler. Best pex to use. Should I use a blower on my damper or not. And a bunch more I cant think of right now.

Any help and/or advice would be much appreciated.

Thanks

 

[Turkeyslayer]

Here are a few more pics of the air intake and outlet. My thought is to put an automatic damper with blower on 4" flex exhaust tube and hook it into the intake.

 

[Turkeyslayer]

Once I get the stove plumbed I plan on enclosing it. I also thought I would build a woodshed onto the front of the boiler and run the rain/snow water off the roof through a double screen and into the OWB (with an overflow). Has anyone tried this? My neighbours also dont use glycol they just put rust stopper in the boiler, I thought I may try that also. I thought that if the pump dies I could just put an electric micro furnace inside the boiler enclosure to keep the water from freezing, and maybe a backup pump on hand with vales on either side of the pump so it could be changed out easily.

 

[woodman6666]

What is that little tank on top? Is it a closed or open system? First thing make sure it holds water. For pump a grund fos 26-96 will do you well. for an exchanger whatever fits in your plenum that is made for water to air exchange. Underground lines go with the good stuff from central boiler or logstor. I would highly recomend welding some steel studs to the outside to resemble a small shed and then spray foam the entire outside, then pole barn steel to finish to the steel studs. What is going on with the dryer vent and the long square tube out the back?

 

[PLAYINWOOD]

It needs insulation big time,your heating the outdoors.
I'm not sure glycol is even legal for home use, I know everyone here tops up with a garden hose periodicallyor buckets at the dairy farm.
They put a "conditioner" in for the summer.
Besiedes eating massive quantities of wood I wish I knew more about them.

 

[H-Ranch]

There's something about using a propane tank to build an OWB that just makes me feel good. :hmm3grin2orange:

I would guess less than 450 gallons capacity unless the firebox is really small. Is that extra capacity in the tank above? I'm curious because it doesn't appear that it's heated. I run mine at 150 degrees - most run higher than that but that seems adequate for my situation (2500 square foot house with 20-30' ceilings throughout.) Don't go cheap on the PEX - I think that's the best money you can spend on it. I used a blower though it can be done without and it will operate even if the blower doesn't run. I used a digital aquastat which I also like. Simple has it's advantages too so it depends on what you want. You can get a heat exchanger for the furnace plenum online or at a local dealer depending on the size for around $200. For the hot water it sounds like the plate exchangers are prone to clog up over time so I'm planning a sidearm (still haven't gotten to that.) Definitely do the quick-change valves on the pump and keep a spare on hand. Mine was $70 and is good insurance as it's really the only failure that will prevent you from using it. I don't see the need to run drainwater into it as I only add a few gallons for the whole heating season. I was concerned about freezing if I went away the first winter, but now I've been gone for a weekend to come back to 100 degree water so it's not a problem (as long as it's circulating anyway.) May want to consider insulating the front and the door also even from the outside if needed.

I would recommend mounting it 18-24" higher on the concrete pad. It looks like you'll be bending down a lot to load it. Best advice I got from my buddy who built his.

Oh, and where are you going to mount the tractor seat so you can just sit there enjoying watching it??

Here's mine with some more info in the thread: http://www.arboristsite.com/firewood-heating-wood-burning-equipment/143845.htm#post2359605

 

[dave_dj1]

All of the above is sound advice, I tend to not like a blower on the draft, I think a solenoid actuated mechanism that will close with a power failure would suit me better.
Keep us posted and of course we love pictures!

 

[H-Ranch]

All of the above is sound advice, I tend to not like a blower on the draft, I think a solenoid actuated mechanism that will close with a power failure would suit me better.

I have the solenoid to close off the blower when it's not powered, but what I'd really like is a multi-stage controller to first open the solenoid say if the water got down to 150, then power the blower if it got down to 145. Often I think just having a small amount of airflow would be enough to keep the fire going enough to keep it up to operating temperature without having to run the blower. I would also like to close the solenoid and turn the blower off if it got down to say 125, assuming the fire is out at that temperature.

To Dave's point - you do need a solenoid to keep the intake closed on moderate days so the water doesn't overheat.

 

[AIM]

Ditch the rainwater idea. Just Tee in a water line with a shut off valve into one of your pex lines and periodically top it off.

Ditch the glycol idea. No need. Even if you went on vacation for a month. Leave your water pumps running and your gas furnace would keep the boiler from freezing due to slightly heating the water through your heat exchanger.

The water conditioner idea. You can if you want. I won't tell you to ditch that idea but for one don't know anybody that uses it.

THE BEST PEX YOU CAN BUY!!!!! At least underground. Above ground doesn't really matter a hell of a lot.

Heat exchanger just get what fits but keep the inlet and outlet size the same as your pex or bigger. It doesn't do you much good to run 1" pex if your exchanger only has 3/4" ports.

I really like a blower for my draft. I think a guy can OVERBLOW his fire though if his fan is to big. Mine will blow a 3' tall flame out the chimney when it runs at times. That is just heat out the chimney. I wish I could find one that was about half the RPM's that I have.

Yep. Jack that thing up to waist level

 

[Turkeyslayer]

What is that little tank on top? Is it a closed or open system? First thing make sure it holds water. For pump a grund fos 26-96 will do you well. for an exchanger whatever fits in your plenum that is made for water to air exchange. Underground lines go with the good stuff from central boiler or logstor. I would highly recomend welding some steel studs to the outside to resemble a small shed and then spray foam the entire outside, then pole barn steel to finish to the steel studs. What is going on with the dryer vent and the long square tube out the back?

It is an open system. I think the little tank on top is just for extra capacity or expansion?? It holds water for sure. The neighbour was using it up until this spring to heat a 3000sq ft ranch. But a series of unfortunate incidents had him moving out, so I bought the unit off him before he left. The dryer vent was attached to a small squirrel fan that he used for intake air, and the long square tube is for unloading ashes (not sure if it works though).

It needs insulation big time,your heating the outdoors.

It came with an insulated shed, I figure I will reassemble/revamp after I run the lines and such.

There's something about using a propane tank to build an OWB that just makes me feel good. :hmm3grin2orange:

I would guess less than 450 gallons capacity unless the firebox is really small. Is that extra capacity in the tank above? I'm curious because it doesn't appear that it's heated. I run mine at 150 degrees - most run higher than that but that seems adequate for my situation (2500 square foot house with 20-30' ceilings throughout.) Don't go cheap on the PEX - I think that's the best money you can spend on it. I used a blower though it can be done without and it will operate even if the blower doesn't run. I used a digital aquastat which I also like. Simple has it's advantages too so it depends on what you want. You can get a heat exchanger for the furnace plenum online or at a local dealer depending on the size for around $200. For the hot water it sounds like the plate exchangers are prone to clog up over time so I'm planning a sidearm (still haven't gotten to that.) Definitely do the quick-change valves on the pump and keep a spare on hand. Mine was $70 and is good insurance as it's really the only failure that will prevent you from using it. I don't see the need to run drainwater into it as I only add a few gallons for the whole heating season. I was concerned about freezing if I went away the first winter, but now I've been gone for a weekend to come back to 100 degree water so it's not a problem (as long as it's circulating anyway.) May want to consider insulating the front and the door also even from the outside if needed.

I would recommend mounting it 18-24" higher on the concrete pad. It looks like you'll be bending down a lot to load it. Best advice I got from my buddy who built his.

Oh, and where are you going to mount the tractor seat so you can just sit there enjoying watching it??

Here's mine with some more info in the thread: http://www.arboristsite.com/firewood-heating-wood-burning-equipment/143845.htm#post2359605

Thanks for the info. I will definitely check out your thread. The tractor seat fell off my planter in the spring and thats just where it ended up, I may have to leave it there so I can watch the fire though, lol.

Ditch the rainwater idea. Just Tee in a water line with a shut off valve into one of your pex lines and periodically top it off.

Ditch the glycol idea. No need. Even if you went on vacation for a month. Leave your water pumps running and your gas furnace would keep the boiler from freezing due to slightly heating the water through your heat exchanger.

The water conditioner idea. You can if you want. I won't tell you to ditch that idea but for one don't know anybody that uses it.

THE BEST PEX YOU CAN BUY!!!!! At least underground. Above ground doesn't really matter a hell of a lot.

Heat exchanger just get what fits but keep the inlet and outlet size the same as your pex or bigger. It doesn't do you much good to run 1" pex if your exchanger only has 3/4" ports.

I really like a blower for my draft. I think a guy can OVERBLOW his fire though if his fan is to big. Mine will blow a 3' tall flame out the chimney when it runs at times. That is just heat out the chimney. I wish I could find one that was about half the RPM's that I have.

Yep. Jack that thing up to waist level

Thanks for the info. I plan on putting a manifold in the basement for future expansion so I may be able to jack a water line in there for topping up the boiler.

 

[Turkeyslayer]

All of the above is sound advice, I tend to not like a blower on the draft, I think a solenoid actuated mechanism that will close with a power failure would suit me better.
Keep us posted and of course we love pictures!

I am still undecided about the fan. I have heard they burn alot more wood when they have forced draft. A neighbour has an auto damper with fan, but says he doesnt run the fan. I think that might be the route I go also that way I hae the option of running the fan if that is what the stove likes best

 

[Turkeyslayer]

Well I found a length of insulated pex locally, left over from an install $5 per foot vs. $16 for new. I am heading out now to go check it out. It is commercially made stuff. I think it may be this: 1" HeatSeal Insulated PEX Tubing - Dual | HeatLink (Canada)

 

[Turkeyslayer]

That worked out well. Got the same line I priced yesterday at $16 per foot for $4 per foot. And it is the length I need

 

[Turkeyslayer]

So the pex I got is ecoflex. Anyone ever use this stuff?? Opinions??
Ecoflex - Pre-insulated PEX pipes from Durotan
http://www.durotan.ltd.uk/downloads/Pre-Insulated_Tech_Guide_Jan_2012.pdf

 

[H-Ranch]

So the pex I got is ecoflex. Anyone ever use this stuff?? Opinions??

It sure looks good - I think I'd be thrilled to get that at $4/foot. I can't speak to it's heat loss comparisons to other products.

 

[Turkeyslayer]

I am definitely pleased with that score, couldn't have worked out better.

I made a bunch of phone calls today and think I have a bit of a handle on what I need for the install. One thing I am undecided about is whether to get the high efficiency circ. pump (grundfos alpha) or not. The sales guy says the high efficiency pump will save $1000+ in hydro over 10 years.

 

[H-Ranch]

I am definitely pleased with that score, couldn't have worked out better.

I made a bunch of phone calls today and think I have a bit of a handle on what I need for the install. One thing I am undecided about is whether to get the high efficiency circ. pump (grundfos alpha) or not. The sales guy says the high efficiency pump will save $1000+ in hydro over 10 years.

Sketch out what you think you need - all elbows, fittings, valves, and so on. Then plan to go to the store several times to get the stuff you forgot. :msp_tongue: I wish I had installed a couple more valves if I need to disconnect for any reason.

Wherever the PEX enters the house, make sure you leave room for expansion. That pipe will grow a couple of feet depending on the length of your run and the temperature. Same for going to the furnace. Don't fix the pipe down too firmly as it needs room to move.

Have to weigh the cost of the pump vs. expected savings. Also have to figure replacement cost and cost of having a spare pump around as they don't last forever. I don't know that I would save $100/year.

 

[Turkeyslayer]

Sketching it out is a good idea, and I never thought of the expansion of the pipe. I will keep that in mind for sure. I am hoping to start to get some of the parts tomorrow afternoon. Today was measurement day, measured the plenum on the furnace, distance from proposed pex inlet in house to furnace and wate rheater, ID and OD of air intake of stove and pex line.

 

[hanniedog]

Someone on hear posted one made from the whole 1000 gal tank. Open up the end put whole logs in, think he had 3-4 week burn times.

 

[Turkeyslayer]

That might be woodman6666, he has a few huge units.

Well today was an expensive day I bought everything I think I will need for the install and I bought a 600sq ft spray foam kit. I plan on spray foaming the whole outside of the tank with a multiple layers of foam (I think around 7-8") Each 1" layer is supposed to be r 5.48 which should put me somewhere close to r 40. Then if I build an insulated shed around the unit I should be able to keep the temps up fairly easily making the wood monster a bit more efficient.