OWB Wood Usage

[boyland]

hi All,

I built my own Wood Burning boiler following the DEB Design Plan IV boiler my burn box is 2x3x3 with a 24x24 door.

My water jacket is about 120 gallons.
I heat ahouse 4500 SQ pool, spa, and hot water with it.

I burn a lot of wood I mean 2 cords a week during the cold periods my burn times stink 4-6 hours.

My unit is a natural draft unit, I ahve tried adding grates which basically burn up in a few weeks.

I am ready to install a blower assembly but I am looking for suggestions on improving the efficiency of this unit. I expected to burn a lot but I sure would like to get 8 hour burn times out of it so I can at least get a full nights sleep.

My smoke stack is located on the top in the front closest to the door. I have a deflective plate that seperates the burn chamber from the exhaust so that air goes to the top then across the plate to exit.

I ahve measure the stack tempature at arou 400-450 degree my stack is 9 foot tall my inlet opening is 8x8.

I burn mostly hardwoods some season some not.

Hit me with your suggestions and opinions,
I have tried adding
additional deflection works to a point however seems to increase cresote build up
reducing the intake extends burn times never hit set point temp
reducing the exhaust works well for an extremely hot fire once it cools problems seems like it cannot ever get going again.

I am ready to install an intake induction blower and reduce the exhaust again which seems more the shaver design.

Let me know your thoughts. Still trying to learn how to make this thing run like a pro.

 

[ericjeeper]

Dude how much was it costing you to heat prior to that magic box?
All them btus are going somewhere, either up the flue, Into the heating load or into the ground through your piping to the house and such.
How is your boiler tied in? To a air to water HX? or radiant in floor of some sort?
You certainly will not benefit from a forced draft, as it sounds to me like it has one hell of a draft as it is.. Figure as often as the door gets opened to feed that crack whore..My goodness.
When it gets cold here I have burned 2 face cords in a week, and I had a fit at that. But as most of the guys here know,.. I keep my 3200 sq. Ft house toasty. Heck my garage is 75
Are your line sets insulated?

 

[Butch(OH)]

2 cords a week? 4'x4'x8' 128 cubic ft cords? whoa! do you feed it with a loader? There is a guy down the street that is heating his rental business, a shop and two rentals with a big Hawkins Energy unit one and from watching his pile go down I'm guessing he is using a couple cord a week. Your heating a big house, pool, spa and domestic, that is a big load. I just went out and measured my pile when I read this and heating 2500 ft to 75, workshop to 60 and domestic I have burned 8.25 cords of mixed ash,oak and sycamore since September 1. I am guessing that if I shut the shop off and the domestic I could be heating the house with half that much. With four taking long showers and washing machine going all the time domestic is a big load. a week ago it was pure cold here, below zero about every morning and 17 below once. I think I burned up 2/3 of a cord that week guessing but my neighbors gas burners never shut off. You could have some efficiency problems with your unit but I suspect a big load, There are no magic baffles or tricky things in my Woodmaster. Just a round chamber and one baffle to keep the heat from going straight up the chimney.

 

[slinger]

When it's cold (O around here) I put in a wheel barrow (contractor size slightly heaped) full in the morning and night. Might throw a few pieces on at noon if I'm home.

Hardy H2 heating 1660 upstairs + full basement.

Closed cell urethane insul. walls(2")and ceiling(3").

On track to burn 8-10 cords this winter (middle of Oct till??)

Also heats hot water for domestic use.

 

[boyland]

big load

Yeah I know it is a big load, I cannot really say exactly how much used before because my house is zoned so I used to keep part of it cold like 60 and living area.

Yes 4x4x8 cord.

I am not really concerned about the amount but I sure would like to extend the burn time at least to 8 hours. How large are your burn chambers.

I was thinking the forced draft would allow me to choke off the exhaust more and force more air increasing the heat level and reduce the chimmeny heat.
But that was question. I went ahead and installed the blower I can control the input a lot more that an open door. Basically my door is open all the time.

After you load and leave what do your temp got to 185 shut off and what is the temp at the next load?

I am seeing quite lare variations and without grates I get this charcoal size coals that just build up. I built my unit much like a central boiler but I had never seen one operate before building mine and I appreciate any feedback as I have noone to bounbce ideas off of. Glad I found this place

 

[Butch(OH)]

I think mine is 38" x 44" The controller is currently shutting the draft off 170 and turning it on at 160. The coldest we have had around here since I bought it was a week ago and -17. I think the draft was on maybe 1/3 of the time, certainly not half. This of course has to do with loads. On any unit with over fire draft you will have the coals build up unless you feed it very carefully only what it needs. They will burn down if you dont feed it. I load mine twice a day as a rule. Have never had to fill it, usualy just over half unless it is going to be REAL cold. I dont load it by temps but by time, before work and after supper. One thing I forgot to mention is youir underground installation. Are you seeing any snow melt over your lines? Are they insulated and dry?

 

[boyland]

Butch I insulated my own pipes. I put them in a 6 in title wrapped with foam insulation and then wrapped with reflectix foil insulation. I lose about 1 degree in temp diff between the boiler and house the boiler is 70 feet from the house.

After installing the blower this evening I am noticing a major difference in my stack temp my stack is a 8 inch square tube steel pipe.

Before the blower I was seeing 400-425 exterior temp that temp is now 200-225 almost 200 degree difference and when I look in the boiler I see a lot of flames.

I am beginning to think the blower controls the burn.

Butch was are are temp difference on the water between loads?

 

[blakey]

Your water capacity is pretty small at 120 gal. You need something more in the 400 gal range, in my opinion.

 

[AIM]

Try dropping your water temp to 130° or 140° and see what happens.
I run mine at 130 or 140 (I play with that a little). I tried to raise the temp up a couple different times and my wood consumption went way up. And I mean WAY up.

 

[boyland]

I have an 2 settings one is set at 180+- and the other is setat 150+-.

I can try reducing it to the lower one but before the fan I had heck of time keeping up with the house. But i am seeing more consistant heat so far with the blower.

My pool is inside and the spa is outside.

I will try that this evening and see if I notice any difference in the ability to heat the house versus the water temp. I raised it thinking I would be able to get the house at a better temp.

I 4 furnaces set is different zones, pool room set at 67, bedrooms set at 70, middle area set at 69, living area set at 71.

 

[Stihl310]

I'm no expert but your boiler sounds way undersized for what your trying to do... I will only be heating a 1700 sq/ft house, but my water cap will be 140-150 gallons...

 

[Windwalker7]

How far does your flue go down into your fire box?

If it is at the top then alot of your heat is going right out.

 

[Stihl310]

How far does your flue go down into your fire box?

If it is at the top then alot of your heat is going right out.

Thats the one thing I did on mine, I believe the pipe sticks down in the firebox about 8-10 inches... I figured if it doesn't work, then I can always just cut it back some...

 

[boyland]

mine does not stick down in the box

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This is kind of what my boiler looks like door and exhaust face the same direction and the water circulates through my door also.

I ahve the exhaust closed down to about 1/2 of the 8 inch exhaust. size so like 4x6 there is over lap from the box. The water capacity is low I wish I had made it larger I think I can accomplish this by adding storage inline. What do you think about doing that?

 

[November Wolf]

I think the only way to increase your burn times is by having a larger water jacket. Putting some water storage inside is a good idea. I would at least put in 100 gallons minimum.

 

[ericjeeper]

I honestly feel you have way to much load..
I asked earlier.. How much was it costing you previous to the wood.. To heat all of the above?
This will give us a true BTU count basically..
You are asking for a whole lot out of a small unit.

 

[boyland]

So far the fan has help a lot increasing the burntimes almost 1/3. I am now getting close to 8 hours yeah....

Before I would spend on average 400 a month for gas or about 400 therms during the colder parts of the winter. Now this was heating the house at a lower temp and keeping the pool at 62.

With the boiler I try and keep the house warmer as layed out above in a previous post, so I would expect 20% more demand than before so I would say 480 therms would be usage during dec-feb each month.

I had planned to add additional water capacity inline if necessary, so a burn chamber of 2x2x3 is smaller? I kind of thought that was in the middle, the water jacket I agree is smaller than I wanted I wish it 2 times the size.

I have 2 new stripped water heaters 50 gallons that I had planned to add inline sounds like I should do that this weekend.

 

[November Wolf]

Please let us know how that works out for you.