Building my own OWB - the lowdown

[cleanburn]

You should only need one pump for the boiler

 

[trialanderror]

You should only need one pump for the boiler

one pump per zone you mean? i'm going with a 2 zone to begin with. then possibly 3 or 4 zone.

Also highly considering a high volume of water to 'store' the heat from the wood you could say..

i'm shooing for a 500-800 gallon system, with 100gallon in the boiler itself. Lots of insulation as well

36 cubic feet of poly is ~$700, r value of 7.

I think i'm going to install the 1". i don't think i'll ever use 1.25" pex. Maybe if i need to pull a tremondous amount of BTU per hour off the water, then i might need volume per minute to move around quickly. but for 3 or 4 100K exchangers, operating randomly, never at once, and such a massive amount of stored BTU's in the water, i shouldn't have a problem.

 

[trialanderror]

It could be 10 times that much wood in the cold weather to heat all you want to heat. I know how much I use, It would be quite a job to come up with 2 or 3 times as much wood. Looks like a great project, I admire anyone who can fabricate something like that.

my mom's quite forgetful, and she left the door open on the woodfurnce inthe basment 3 times. each time we had a chimmey fire....

i'll burn a few more sticks to have a house to live in.....

 

[cleanburn]

one pump per zone you mean? i'm going with a 2 zone to begin with. then possibly 3 or 4 zone.

Also highly considering a high volume of water to 'store' the heat from the wood you could say..

i'm shooing for a 500-800 gallon system, with 100gallon in the boiler itself. Lots of insulation as well

36 cubic feet of poly is ~$700, r value of 7.

I think i'm going to install the 1". i don't think i'll ever use 1.25" pex. Maybe if i need to pull a tremondous amount of BTU per hour off the water, then i might need volume per minute to move around quickly. but for 3 or 4 100K exchangers, operating randomly, never at once, and such a massive amount of stored BTU's in the water, i shouldn't have a problem.

You will need one pump for the boiler. You will need one pump for your house, the water from the boiler and your house shouldn't normally mix depending on how you set it up. You could put multiple pumps for multiple zones or just use zone valves. I have zone valves in my house.

Why so much water? Again water is only used for storing heat, the only main advantage to storing all that heat is that your woodstove/OWB cycles less often. This means a longer on cycle and a longer off cycle, if you try to store too much you could have to load your stove twice before you have stored enough heat in your water....if you plan on doing 800 gallons your firebox should be roughly atleast 40-50 cubic feet, that is just an estimate off the top of my head....but a smaller firebox than that and you'll be loading it twice before all your water is 185 degrees....you could also possibly store so much heat your fire goes completely out before your stove turns on again (very long off cycle)....and you'd have to relight your stove everytime you fire it up....500 gallons is A LOT of water....

 

[trialanderror]

why would the fire go out if there's wood in it?
the damper woudl close and the fan shuts off, and it does the classic 'smoldering' . As long as i check on it every 12 hrs, it should never go totally out....

water chills, boiler cycles, heats the water, shuts back down.

that is the point of using so much water. So it won't cycle so often. yeah, it's going to take a long time to get heated. but the stored BTU's will be much higher with so many gallons. Assuming go crazy insulating everything.

FYI, the noodle 8ft foam pieces from CB has an R-value of 13. Or so says one of the techs.....

 

[blakey]

I agree it is better to have the fire outside, I have an owb myself. Just from a couple of your comments I thought you may be grossly underestimating the wood usage heating that kind of square footage. I won't mention it again.

 

[cleanburn]

why would the fire go out if there's wood in it?
the damper woudl close and the fan shuts off, and it does the classic 'smoldering' . As long as i check on it every 12 hrs, it should never go totally out....

water chills, boiler cycles, heats the water, shuts back down.

that is the point of using so much water. So it won't cycle so often. yeah, it's going to take a long time to get heated. but the stored BTU's will be much higher with so many gallons. Assuming go crazy insulating everything.

FYI, the noodle 8ft foam pieces from CB has an R-value of 13. Or so says one of the techs.....

Well the fire going out depends on a number of things, how long it is off for, how air tight your firebox is, how much brick or no brick you have....I was just saying your fire will be smouldering for a longer amount of time than a "normal" OWB because your off cycle will be very long due to all your stored water. Depends on how close you set your aquastat to turn on and off your stove though too....but if you set your aquastat closer then you defeat the purpose of having the water. You could effectively store heat just by also increasing your range (stove comes on at 150 off at 180 instead of say on at 170 and off at 180) You can do the BTU math on that one too

 

[trialanderror]

I agree it is better to have the fire outside, I have an owb myself. Just from a couple of your comments I thought you may be grossly underestimating the wood usage heating that kind of square footage. I won't mention it again.

more like 3500 sq ft.
i overestimated because of poor building insulation.


and i agree. set a the on/off further apart.
I'm buying new fiber rope for the ash door and firedoor. going to use 6" of urethane spray-foam on all sides. Plus install a damper with the blower motor so it'll shut airtight, won't draw air past the draftblower. I've read from others that always suggest a draft fan when buying one, especially if building one...

150, even 130F water will be better then nothing.... I don't have storage tanks at the moment. Between the boiler and plumbing, i may have 200gallon at the most. But i have loads of ballvalves, so, i'll just set it up to add tanks later if needed be.

I have $0.00 into this burner. Well, a little bit invested. 2 miles of driving and 5 minutes of time.. and i don't have $15,000 to buy one right away, nor $4000 for material to build a 120Cubic foot monster... . I'm burning $3000 a year in propane, 2 years of this setup will allow me to save up to buy one or make one. what have i got to loose? couple of weekends of fukin' around. Both need power and plumbing, so the it's not like that'll be a waste of time or money.

 

[DLav]

1 1/4 pex? or 1"?

1" or 3/4" copper for inside the building?

I don't know the technical aspects of 1 1/4 versus 1, but the company I bought mine from recommended 1 inch and the fittings on my heat exchanger are 1 inch, so I used 1" for everything. It depends on where you buy your fittings, but most of the home improvement stores Menards, Lowes, etc have better selections when it comes to 1", they don't seem to stock as good of selection in 1 1/4. Attached are some pics I took of my pipe last fall before I got the trench backfilled, there was 180 water running through the pipes when I took the pics, and the snow never melted. I emailed the pics to Foam Plus.

 

[trialanderror]

looks impressive. Really looking forward for you to post incoming and outgoing water temps If it's working that good for you, maybe i'll just by the stuff from foam plus.

 

[trialanderror]

aqua-stats

Alright, welded another 12" on the backside of the boiler, so the rear of the firebox will heat some water instead of dead space, plus give me a lower temp area to actually spray foam and not burn in flames... and another 32gallon on the boiler instead of stored somewhere else in the system.

it has a draft on the front, and a small blower on the rear. probably close the back and use the front or vice versa. probably use the front, blower will have a tendency to blow the ashes a bit?

i read some where it's best to have 2 aqua stats; one for the draft, another for the blower. draft 180-195, if it can't keep up, 2nd stat @ say 160-185 will call for blower assist. Naturally, i was going to have the draft on the blower so when both stat's are satisfied, everything closes somewhat air tight., i

question is do they make a aqua-stat that has 2 switches, each temp setting independent.
or should i buy 2 single switch's?

Honeywell for rep?
a better company maybe?

i would like to go with 110v instead of 24v which needs relays and a transformer blah blah blah.

oh yeah, digital? mechanical w/dials?

 

[fletcher0780]

Why not use a digital programmable 2 stage aquastat like either of these:

http://www.rancoetc.com/ranco-etc211000000-stage-p-105.html?osCsid=b9860bd0f43c32c7deff9fdab6f7c679

http://www.dwyer-inst.com/Products/Product.cfm?Group_ID=125&Product_ID=289&sPageName=Ordering

 

[trialanderror]

http://www.rancoetc.com/ranco-etc211000000-stage-p-105.html?osCsid=2dffeae47b0da6ac378ac10875951839


couldn't find the right one on your first link.

awesome pick though. Might even order the pre-wired one for convenience ...
pretty much set. gonna call up CB and ask them for a draft solenoid.

 

[fletcher0780]

http://www.rancoetc.com/ranco-etc211000000-stage-p-105.html?osCsid=2dffeae47b0da6ac378ac10875951839


couldn't find the right one on your first link.

awesome pick though. Might even order the pre-wired one for convenience ...
pretty much set. gonna call up CB and ask them for a draft solenoid.

Don't go through CB, they're expensive. Get it here: http://www.drillspot.com/products/42984/Dormeyer_2005-M-1_Laminated_Solenoid

 

[trialanderror]

any particular reason you posted that one? i see theres quite a selection.

what's the differences? able to pull more leverage at the expensive of pulling more amps?
stroke?

 

[fletcher0780]

any particular reason you posted that one? i see theres quite a selection.

what's the differences? able to pull more leverage at the expensive of pulling more amps?
stroke?

I was just trying to give you an alternative option to buying from CB. They have a tremendous mark-up (at least my local dealer) on almost everything they sell. The Dwyer controller I gave you a link to is used by CB and they sell it for more than double what you can get it for. Just like their Ashtrol product, 1 gal for thirty something bucks (I'm pretty sure it's just lyme).

It's a pretty popular solenoid among OWB's. I modified the blower on my Shaver to include a automated damper and used that one. The thing has a tremendous amount of power and would be able to lift a heavy damper plate with ease. I've been using it for a couple months now and works very well.

 

[blakey]

Actually I was surprised when I purchased a solenoid for my CB a couple years ago, it was only $35 Canadian from the dealer.

 

[uglydukwling]

Blakey, who is your CB dealer? I need to add a solenoid to mu boiler, and that seems as good a place as any to get it. Do you have the part # handy?

 

[blakey]

pm sent

 

[Sawmill]

There is a place in Grand Rapids call Arevon ( not sure if I spelled it right) that makes foam sheets and all shapes. I bought my insulation from them and I had them make it so I had an R 10 value all around the pex. I think it is the same stuff you buy at Bitley. They will make whatever length you want up I think 12 foot. It has been 4 years since I bought it but I had them make mine 8 inch Dia with holes down the middle for the pex and then I used a plastic sleeve to cover it. When I bought this foam I paid 50 cents a foot. I am sure the price is higher now but may be worth checking out.