Damper Control OWB

[Stihl310]

New to this site, and currenlty in the process of building an outdoor burner... my question is that I have been reading alot and in some instances guys are wiring up the damper to operate separatly from the burner... for instance... the damper opens at 140degrees, and if the temp drops to 130 then the blower fan engages from a different thermostat... I guess the question is shuold I run the damper and fan in sync so that they both operate at the same temp. Or should I wire the damper in separetly to give the fire a chance to get back up to temp without the help of the fan, then if necessary engage the fan to kick the heat back...

I would think that when the thermo calls for heat I would want to run it back up immedietly with the help from the fan, making me think I should wire them up to operate both at the same time rather than separetly...

Let me know what you all think,

Thanks

 

[ericjeeper]

Welcome to the site

Most owbs have one or the other for feeding air.What type of design have you come up with? fan below the door? damper in the door?How big of tank? How large of firebox?

 

[Stihl310]

The design I was going to use has a fan on the door along with a damper that closes over the fan intake to shut down the air... is this necessary???? or can I just go with a damper alone??? I'll be burning mainly seasoned wood so I don't need to turbo charge my fire to get it burning or anything ... I'm going to be using two steel sleeves for lack of better words, I'll have a 26" diameter fire box with a 40" outer water jacket that will surround the entire fire.... I should get approximetly 120 gallons of water in this setup, basically I'll have a 7" water jacket that completly surroundss the fire. I'll only be heating a 1700 sq ft house so I think this should be more than sufficient, it's a very well insulated house that is using JM Spyder Insulation for all walls, I've got R 42 in the ceilings as well. Currently I'm using propane and can't stand it... just not the warm wood heat I was use to... I'm thinking with the smaller water volume I should be able to decrease the amount of wood I burn in order to keep it at temp.. but I could be wrong...

back to my original question, do you think it is necessary to run a fan on a burner when i'm using primarily seasoned wood? I had planned on wiring one in, but if it is not necessary then I will leave it out.

Thanks

 

[John D]

Stihl,i think you don NEED a blower,but it probably would help recovery time in certain situations.My shaver has just a blower,no damper controls what so ever.Id happlity give up the blower in order to have a damper that shut right down,and opened up on demand.My blower isnt that great if the damer door is shut most of the way,you cant draw enough air thru the restricted opening.

 

[ericjeeper]

I have two small blowers..

Now wishing I had one larger one. I prefer it to ramp up quick rather than have a half smoldering / fire.
Make sure your door frame is extended out from the flat plate of the end of the firebox.. My face warped, so I redid the end with a 1/4 inch x2 inch flat stock to get the firebox face some strength

 

[blakey]

A friend of mine has an owb that was built locally and it uses a blower and a lightweight damper so the airflow opens the damper, no solenoid required. I think it works ok but sometimes doesn't seal that great and it leaks a bit of air, causing his water temp to overshoot. I don't know how other units work but my Central Boiler has a fairly heavy damper that clanks shut when it hits the setpoint. I never have an overshoot problem, it completely kills the air supply. The solenoid is pretty cheap and reliable, I think $35 or so from the dealer. I would think having the blower and the damper solenoid kick in at the same time would give the best control and the least amount of smoke.

 

[Stihl310]

The design I was going to use has a fan on the door along with a damper that closes over the fan intake to shut down the air... is this necessary???? or can I just go with a damper alone??? I'll be burning mainly seasoned wood so I don't need to turbo charge my fire to get it burning or anything ... I'm going to be using two steel sleeves for lack of better words, I'll have a 26" diameter fire box with a 40" outer water jacket that will surround the entire fire.... I should get approximetly 120 gallons of water in this setup, basically I'll have a 7" water jacket that completly surroundss the fire. I'll only be heating a 1700 sq ft house so I think this should be more than sufficient, it's a very well insulated house that is using JM Spyder Insulation for all walls, I've got R 42 in the ceilings as well. Currently I'm using propane and can't stand it... just not the warm wood heat I was use to... I'm thinking with the smaller water volume I should be able to decrease the amount of wood I burn in order to keep it at temp.. but I could be wrong...

back to my original question, do you think it is necessary to run a fan on a burner when i'm using primarily seasoned wood? I had planned on wiring one in, but if it is not necessary then I will leave it out.

Thanks

I guess another question...I haven't found any recomended water jacket size, but I'm thinking 120 gallons should do fine for my house...I'll basically have a 26" diameter x 36" deep circular firebox, so it should be fairly efficient...all my wood is going to be split as well, except the small stuff, so I feel like a 26" dia. will serve me well, I also plan on making my door the full size of 26" to accomodate the wood I'm cutting... at 36" deep I shuold be able to shove two lenghts of firewood in it with room to spare.... Just let me know if there are any other suggestions you have... thanks...

 

[ericjeeper]

Keep the door square

Round door will be hard to hinge.imho
Leave some face at the bottom to hold ashes and coals in. My door is 17x17 and is plenty large. I split my wood so it is really tough to one hand it on the end.. But it can be done by me.Wife no.
I load my wood north to south as opposed to east to west.. So basically I am tossing it in so that it has the sides facing me rather than the ends.I can fit a whole heaping wheel barrel in there with a good bed of coals..
Here is the link to my beat the oilman pics
http://www.pbase.com/ericjeeper/solar&page=all

 

[blakey]

A door that large might be a problem when you get some ashes built up and they will spill out when you are loading. As was mentioned before you will likely want to build out the door at least 6 " or so to lessen the heat on the door and prevent warping.

 

[Stihl310]

Never even thought of coals building up against the door... Thanks for the info...

 

[bowtechmadman]

I would think you'd want the damper to open simultaneously w/ the blower fan coming on. Depending on the size of the firebox you may want a blower/damper for the front and the back of the firebox. I like this feature in my Woodmaster. I get an even burn throughout the firebox.

 

[Tracker83]

My OWB has both a solenoid-actuated damper and a blower. Both are activated/disactivated at the same time. I would think that you would want a true damper to keep the fire choked down properly between burn cycles.

 

[blakey]

The Central Boiler units ( and I imagine most others) have a rope on the door to seal it. Might be hard to make a groove for the rope if the door is round.

 

[ericjeeper]

I built my door out of 1.5x1.5 inch angle 1/4 inch thick

Mitered the corners. Welded it up square then inserted the piece I cut out of the face to make the door plate. Then I used 1/2x1/2 inch 1/8 wall welded to the 1.5 angle to hole my rope gasket. The new 2 inch bar stock welded to the face fits into this slot to seal against the rope.. Works like a charm

 

[Stihl310]

On mine I was going to leave the firebox protrude 3/4" out from the face, then just wrap the round door with a piece of 1/8" that would in turn go around the firebox protrusion, along with the stove "rope" to seal it... Could be more work than I think, but from the CAD drawings I've done it looks like it should seal up....

Anyone have any opinions on my firebox size and water jacket size... sufficinet for a 1700 sq/ft house???

 

[Stihl310]

I'm starting to think the square door even covering the round hole would be much easier... I want it to be as painless as possible

 

[ericjeeper]

How in depth are your fabrication skills?

You know this thing has to be as watertight as a frogs butt. LOL
And it needs to be pretty air tight too..

 

[Stihl310]

You know this thing has to be as watertight as a frogs butt. LOL
And it needs to be pretty air tight too..

Yep,I'm fully aware of all that... I have always been pretty good with stuff like that... I have been tinkering and working on stuff since I was 11-12 years old... I can weld fairly good with a stick welder, but I can do a very good job with a MIG welder which is what I plan on using for this project... The fabrication part isn't the overwhelming part to me... it's the whole hookup in my furnace that I'm still dwelling over...

 

[NC4AB]

I rewired my Hardy H2 to utilize a two stage Ranco Controller.

If my memory is correct I have the damper solenoid set to open when the water drops to 160F, and it closes at 170F. If the damper by itself can't meet the load the fan starts at 155F and runs to 165F.

The two stage setup provides a good match to my system, and in my mind it cuts down on some wood usage. During warm weather the damper only operates, when it gets cold the fan runs in addition to the damper.

 

[blakey]

I use a Ranco controller for my shop squirrel cage blower. It works well but a little tight to fit the wiring if I remember correctly. I got it at TSC. Both stages can be either heating or cooling mode, can be used for a 2 speed fan I believe, adjustable differential, digital display, weatherproof. Very versatile.

http://www.rancoetc.com/ranco-etc111000000-digital-temperature-controller-p-86.html