OWB water temp issues?

[Nickota]

My brother and I are builing our own OWB. We used two propane tanks big one for water jacket swaller one for fire box. Weled out in front with 3/8" plate. We lit the fire yesterday and got the 330 gallons of water warmed up set the aqaustat @ 180 started a pump circulating through 50 ft 1" line a small exchanger with fan. Nothing is insulated at this point,(plan to after all bugs are worked out) just sitting out in frint of the shop it will eventually heat. The water temp at top reached 180 but it seem to only heat to about 140 around the bottom. The suction and return lines are located down in the bottom 1/3 of the water jacket. Pump moves about 12 GPM in this configuration.

My question is will the insulation help equalize the water temp by controlling the heat loss out of the top? Do I need to move suction up towards top? Do most OWB have some variation in temp top to bottom?

Nickota

 

[John D]

Welcome to arborsite!

I think you need to move your suction line near the top,but not so high than slightly low water level will leave you sucking air.This will help move the water from low to high as the pump pushes the return water in the bottom,it will rise as return water flow pushes the water past the firebox,upward,combined with natural heat rising, you will be taking the hottest water off the top and sending it to the shop.
I was considering making an OWB for my shop where I work,If you can take and post/PM pictures of what you did,I'd appreciate it. Im willing to bet your OWB will last as long as any of the commercial units. My intention was to use a 300 lb propane cyl for the inner portion,and the outer,just build a jacket out of .250 thick mild steel 4x8 sheets.

 

[KsWoodsMan]

Insulation might help , some.

The reason the CW inlet is low and HW outlet is high it to get better mixing inside the water jacket. If you are pulling 180* water out from the top, the circulating water will pass around the firebox reheating it. Instead of just letting it sit at the top as you pull from the middle you could be getting more heat by pulling from near the top.

And , Welcome to Arboristsite.

 

[Nickota]

Thanks guys, I will try to post some pics later today, I have to get to work in a few minutes. The reason we started with our suction and return down at the bottom was just looking at a Taylor model and a CB. I assume circulation will be the key. We plan to put a few taps in and make the suction height adjustable before we insulate and install.
The propane tanks were available took a 1000 gal and 330 gal and split in half. We will end up with a stove each.

 

[showrguy]

my mahoning has a 007 that pulls from the bottom and returns to the top and it runs constantly to keep your internal water temp consistant, i would definately do that if i were building one as you are...
i set a owb for my neighbor last week it's a heatmore brand (i think), he's having issues with his takeoff temp. right now he has his aquastat sat at 170 but his temp coming out is only 140, it has no internal circulator ?? the supply they had marked to come out of the bottom side of the unit ?? i think i got him talked into adding a pump and changing the supply/return from low-hi to high-low........hope that helps..

 

[John D]

my mahoning has a 007 that pulls from the bottom and returns to the top and it runs constantly to keep your internal water temp consistant, i would definately do that if i were building one as you are...
i set a owb for my neighbor last week it's a heatmore brand (i think), he's having issues with his takeoff temp. right now he has his aquastat sat at 170 but his temp coming out is only 140, it has no internal circulator ?? the supply they had marked to come out of the bottom side of the unit ?? i think i got him talked into adding a pump and changing the supply/return from low-hi to high-low........hope that helps..

If your using a suficiently sized main circulator,you should be able to use the main circulator to kill 2 birds with one stone by letting it run full time.Positioning the inlet and outlets in the proper locations is all that should be needed.Running an additional circulator is just an added expense,and electric cost.The one should do it unless the unit is huge,and in that case,it should be plumbed with bigger lines,and a higher GPM pump anyway,which should move enough water around the firebox to keep from needing a second pump. I only say the above because i am a miser, I am anal about my electric usage,I hate wasting power to run circulators.Our electric here is thru the roof now,its bad enough we need to run 2 circs full time with an OWB and a heat exchanger.,I just wouldnt want to add a third.

 

[cleanburn]

showrguy,

which heatmor does he have? I have a heatmor and it runs fine, I run it from 185-165, pulls from the bottom and puts water in the top.

Nickota, what you are seeing is called water stratification, the water is layering in temperature, you need to change your lines so you have a better flow system. I would suggest pulling from the bottom and putting in water at the top, if that doesn't work quite right, try putting a pipe in the top or bottom line so that it pulls or pushes water toward the front of the stove and pulls from the bottom back. That will help give you a better water flow.

 

[fletcher0780]

showrguy,

try putting a pipe in the top or bottom line so that it pulls or pushes water toward the front of the stove and pulls from the bottom back. That will help give you a better water flow.

I agree, I know Shaver added a pipe to their return line that ran to the front of the water jacket to help create some turbulence and mix the water.

What do you plan to use for insulation? how is your chimney set up, out the top or the back? Either way, try to keep the flue down as low as possible to trap the heat at the top of the firebox. Do you have a blower installed, or are you using natural draft? what type of control are you using to activate the blower/ damper? I have a Shaver, but have been steadily making minor modifications to improve its efficiency. I'd love to see pics when you get a chance.

 

[showrguy]

my unit is huge i guess (sorry, had to laugh) , naw, my outdoor unit holds 350 gal. i have a pair of 009's one pushing inside basement 225ft. away, one pulling at the unit, have 125 gal. nurse tank in basement that all radiant zones come out of with 4- 007's, 009's only come on when nurse tank drops below 137 deg. shuts em down at 140 deg. works great..... guess it all depends on the individual situation/installation....
cleanburn, i don't know which unit it is but it weighs 1600 lbs. empty, i did'nt think he got much for $8,000.00 but he did his research and made his decision, so i guess he'll be happy once he learns to "drive" his unit ??

 

[cleanburn]

my unit is huge i guess (sorry, had to laugh) , naw, my outdoor unit holds 350 gal. i have a pair of 009's one pushing inside basement 225ft. away, one pulling at the unit, have 125 gal. nurse tank in basement that all radiant zones come out of with 4- 007's, 009's only come on when nurse tank drops below 137 deg. shuts em down at 140 deg. works great..... guess it all depends on the individual situation/installation....
cleanburn, i don't know which unit it is but it weighs 1600 lbs. empty, i did'nt think he got much for $8,000.00 but he did his research and made his decision, so i guess he'll be happy once he learns to "drive" his unit ??

Not sure which unit you have, the weight sounds like a 200, but the gallons sounds like an 800

Your stove holds 350 gallons of water?

 

[showrguy]

no, no, my neighbor just got his heatmore, i set it with my backhoe last weekend, his unit weighs 1600 and i think it holds 100 gal. or so....
my mahoning weighs 4000 lbs. empty and holds 352 gal.

 

[cleanburn]

Oh I see. Your neighbor has about a size 200 Heatmor then.

It is YOUR unit that is HUGE.

haha

 

[Nickota]

I don't have a final plan for the insulation we have seen regular pink R-19 used and some foam applications. There seems to be a lot of conflicting reports of which one is best for trapping moisture etc. I have a friend at work who does the insulation design for piping and such, I am going to pick his brain later this week.
The furnace has draft fan on the front and is controlled by an aqua-stat that operates the blower. Temp set point shuts power off to fan and gravity damper seals off the air flow going into firebox. The pump will flow continuous. We can locate suction and return ports anywhere on the jacket we want and do some trial burns before we insulate and install. The goal is to use this to heat the house and shop in the future. My brother is a great welder and insisted I provide the disclaimer that he spent a lot of time on the internal and water jacket welds that must hold water and we just threw the door and air box setup on quick for testing. The final door is being welded up as I type and will be much better to look at.

I can't get the pics to upload! I'll try again later

 

[Nickota]

Second shot at it

 

[Nickota]

This may be better front view the current suction port on right return on left. The aqua-stat is not in the pic bur the well is up on the right pipe nipple in front top right will be sight glass with temp gauge in the future.

 

[urhstry]

Maybe somebody already answered this but would it make a difference if you pulled water off the top on one set of lines and pulled water off the bottom on the other? I know the Shaver has two ports that you could do this with.

 

[mtfallsmikey]

I think that answer may be spot on...There was a brand of oil-fired hot water boiler years ago...company was Harvey-Whipple, that made a boiler similar to that design!

 

[uglydukwling]

Theoretically, you should take the water from the top of the boiler ( that's where the hottest water should be) and feed the return into the bottom. Trouble is, when I hooked mine up that way, it wouldn't work. Mine has a header tank above the boiler, which ensures that the boiler is full and the pump is flooded. Even so, the pump wouldn't draw water from the boiler. I reversed the connections and now it works fine, even though it might be a little less efficient. It seems the pump needed that extra couple of feet of positive suction head to work. An alternative might have been to move the pump to the boiler rather than leaving it in the basement, which would have reduced friction losses on the suction side of the pump, but I took the easier way.

 

[cleanburn]

Theoretically, you should take the water from the top of the boiler ( that's where the hottest water should be) and feed the return into the bottom. Trouble is, when I hooked mine up that way, it wouldn't work. Mine has a header tank above the boiler, which ensures that the boiler is full and the pump is flooded. Even so, the pump wouldn't draw water from the boiler. I reversed the connections and now it works fine, even though it might be a little less efficient. It seems the pump needed that extra couple of feet of positive suction head to work. An alternative might have been to move the pump to the boiler rather than leaving it in the basement, which would have reduced friction losses on the suction side of the pump, but I took the easier way.

Since a boiler heats water and you use that to heat your house....you want to put your coldest water where your heat is to heat it up, so that is why you want to return to the top (where the hottest water is) and take the water from the bottom.

You would not utilize all the water in your stove if you are pulling from the top....

 

[sstan]

I don't understand the last post at all ... the hotter water should be at the top of the boiler and as it goes to the house cools off .. I pump it back to the the bottom of the boiler. Why pull the cooler ( ok not much I don't imagain) into the house .. I am trying to use that heat. My boiler came with very spesific instructions on which ports to use to feed and return.