Yes, ANOTHER OWB build thread... (Tank in tank style)

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Water volume in owb? 2500sf home and 34x48 shop

  • 100 gallons

  • 200 gallons

  • 300 gallons

  • 400 gallons

  • 500 gallons


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breymeyerfam

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Ok, so I have been planning this build for the 10 years I've lived in my house since built. Finally getting around to it! Background: home is roughly 2500sqf with radiant tubes in basement floor (planned on an owb from the beginning). Will be adding a HX in the furnace and a side arm on my electric water heater for DHW. I will also be heating a 34x48 shop to 45-50 degrees (with HX) unless I'm out there, then to comfortable temp (65° couple times a week, a few hours at a time). The boiler will be roughly 100' from the house and 10' from the shop.

Finally, this build will be a tank in tank design. I am using two propane tanks that are 30" and 41" in diameter. The plan is to use forced draft, with a ranco aquastat, and two appropriately sized pumps, one to the house and the other to the shop. I think I have decided on roughly 320 gallons for my water volume in the boiler. Please vote in the poll and comment if you have a good reason for me to change my mind on water capacity...

And yes, I know that it didn't happen without a pic, so here is what I'm working with:
20160716_134035.jpg
 
I have an old Western Pacific stainless. I'm thinking it's the 400 plus gallon model. I would not go smaller that that as it works well for me and I'm doing about what you're doing but also heat another house instead of your shop. I have all the heat I want and that's the best way to be. I know guys who have smaller ones and they feed the beast way too often and I think it's because of small firebox and small water capacity. I can put 54" long stuff in mine. I cut wood at 32" long and split it small enough to handle easily. Lots of pictures of my OWB, wood and equipment I use on here under my name. Make it as long as you can and you can burn almost anything in it. Slab wood is cheap and easy to handle if you can feed 5 or 6" pieces in. I never fill my owb full, I put in what I expect to have heat demand for and when I plan to put wood in it next. Usually burn junk wood (poplar) newspaper flyers and cardboard all summer for domestic water, put a bit of wood in every couple of days. With 400 gallons of water if the fire goes out it takes 4 or 5 days before we notice the water get cold.
 
FYIU, I was planning to build my own and was doing research and looking for supplies and I stumbled onto a used one real cheap. Some places are outlawing them and some people think they are too much work, look around for a used one while you are in the planning stages, you can always sell it once you get yours built.
 
Ok, I cut the firebox roughly 48" deep. And planning to leave the water jacket tank as long as possible. That should give me between 420 and 430 gallons.
20160717_170930.jpg
Getting used to my new plasma cutter, but the cut didn't turn out to bad.
20160717_163122.jpg
I cut the tank at roughly at 40° bevel. Made grinding fairly easy. Small tank is ready to weld to the face plate.
20160717_165200.jpg
The fit is pretty good, should make for some easy welding.
20160717_173215.jpg
 
Ok, I cut the firebox roughly 48" deep. And planning to leave the water jacket tank as long as possible. That should give me between 420 and 430 gallons.
Getting used to my new plasma cutter, but the cut didn't turn out to bad.
I cut the tank at roughly at 40° bevel. Made grinding fairly easy. Small tank is ready to weld to the face plate.
The fit is pretty good, should make for some easy welding.
Looks good - keep sending the updates.
 
***I am not taking credit for these welds on the fire box. My brother is a union pipe fitter and welding instructor. I told him I was going to mig weld this together, and he proceeded to show up at my place with 40lb of welding rod and said "f**k if you are"! So, moving on. Tacking up the firebox.
20160718_175759.jpg
Root pass with 6010:
20160718_191829.jpg
Finishing second pass:
20160718_201250.jpg
20160718_201250.jpg

Second pass complete:
20160718_201640.jpg
Second pass and cap is 7018 rod.

Cap pass 1/4 complete. Done for the evening. Forgot to snap a pic of the cap pass so far. Will get a pic later.
 
***I am not taking credit for these welds on the fire box. My brother is a union pipe fitter and welding instructor. I told him I was going to mig weld this together, and he proceeded to show up at my place with 40lb of welding rod and said "f**k if you are"! So, moving on. Tacking up the firebox.

Root pass with 6010:

Finishing second pass:
20160718_201250.jpg

Second pass complete:

Second pass and cap is 7018 rod.

Cap pass 1/4 complete. Done for the evening. Forgot to snap a pic of the cap pass so far. Will get a pic later.
You know the reason for not using mig on pipe welding especially a root pass correct?

Sent from my SAMSUNG-SM-G890A using Tapatalk
 
I don't the reason other than your supposed to stick weld pipes. I've always wondered why. I remember a few years ago an experienced welder at our shop mig welded up a testing cap on a pipe and it had leaks.
 
I voted 300 gal then read your description and changed it to 400. Sounds like you have the appropriate size now being 400+. Welds look good, slot better than one my buddy is building. His looks like the tin man took a **** on it. Good luck.
 
I don't the reason other than your supposed to stick weld pipes. I've always wondered why. I remember a few years ago an experienced welder at our shop mig welded up a testing cap on a pipe and it had leaks.
Most high pressure are a tig root then hot pass with tig or stick or once in a while flux core same with caps. The reason is being able to see you're not cold lapping the joint like you can hard wire mig. All hydraulic joints I do on my equipment and tubing I do with tig less chance of a cold lap or pin hole in the weld.

Sent from my SAMSUNG-SM-G890A using Tapatalk
 
Mostly stick welded because stick is easiest out in the field. Plenty of wire feed FCAW setups used too.

I'll be honest, for an experienced pipe welder it's pretty bad welding in those pics.
 
im gonna guess there will be some stresses in that end plate now.... be interesting to see what happens when its cut for the door. id say the weld looks very neat.
 
Good here too.

That was a fun day.

Great lookin build on the burner.
 
Ok, some more progress.

Ports cut from fire box tank.
20160725_201145.jpg
Plate cut and partly welded in. (This is second pass, forgot to take a pic of root)
20160725_182849.jpg
Cap:
20160725_201304.jpg
Door opening cut. 20" door
20160725_193956.jpg
That is all for now...
 
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