Increasing efficiency of Heatmor OWB

[2012outdoorsman]

Hi All,

Was figuring with how many people are on here who just are never happy with things the way they are and always trying to make them better that you'd be a great group to ask this question to.

I'm looking to add a variable blower control to the blower motor to my forced draft and was wondering if anyone has done this.

I feel this would increase the efficiency tremendously. When my stove gets going I can hear water boil insidea it. It may be in the door but I don't think it's just there. I have multiple temp dials and overall the water does that get above 180.

I can also see flames come out of the chimney from time to time while rare it does happen.

These situation don't happen every time the stove kicks on but do happen usually in the middle of the days when all the wood has dried out completely but hasn't burned down much.

I feel the blower is just pushing to much air for how quickly the water can absorb heat. I also feel that it is just pushing a lot of heat right out of the chimney instead of absorbing it. The stove is ten years old and everything is from when it was brand new.

I think a time based control would be awesome but I really want to keep it simple. Below is the controller I was looking at. I've yet to check what the amp rating of the blower is but I think it's below 2.5amps but may buy the 5amp one anyway.

https://www.amazon.com/gp/aw/d/B000...g_2?ie=UTF8&psc=1&refRID=1RASESWS3V54PCRWDE4Z

 

[dave_dj1]

Instead of going through all that why not just convert it to a manual draft? I have never been a fan (pun intended) of forced draft induction as I feel it burns a lot of wood unnecessarily.
I don't even like automatic opening dampers or draft control if you will. I set my amount of air to the conditions required IE: outside temps.
I don't own a OWB but I do have an outside forced hot air unit that I fabbed together a few years ago. I started with a Fawcette wood hot air furnace and built an insulated box around it. It has a thermostatically controlled draft door but I don't have it hooked to a thermostat, I have it wired to a timer like in your bathroom fan. I load it up, set the timer for anywhere from 5 min. to 30 min. depending on a few circumstances, outside temps, inside temps and what is going on in the stove. I have learned to let the wood burn almost to ash (I always have a good bed of coals) before loading it. I have a 1/2" hole in the door that lets in the combustion air when the draft is closed. It took a while to figure out how many 1/2" holes to leave open (the door already had a few which I have plugged) I take an extra bolt out on extremely cold days although I didn't last night (it was -15 here this morning) and at 7 this morning it was still 72 in the house.
I had an add on water furnace once in a house we lived in that had an automatic draft and it consumed a lot of wood, I cut the power to the draft control and installed a long bolt that I could thread in and out to adjust the draft, it cut my wood usage by half.
Just a thought.

 

[djones]

I like the idea of a variable speed controller. I had been thinking of a 2 speed blower but can see where a variable might be better. I do have an off switch wired into my blower fan so that it does not come on during the night, if I remember to turn it off after my evening fill up. A full blast from my blower will blow out a raging fire of pine after a while whereas a slower blower will keep it burning better. With the hardwoods I like to keep the blower on all day but don't always need a full blast. I do have a speed controller in my shop that I may have to give a try. I just don't feel like taking the door apart to get to the blower just at this moment with temps in the neg to o° range. When I try it, I'll let you know the results.

 

[2012outdoorsman]

I think it would require a lot of work to go to natural draft. The natural draft owb usually hold much more water than the forced draft. I like the idea behind the forced draft but my FIL owb uses half the wood that mine does but I will attribute some of that to a newer house and insulated foundation.

I guess not many have thought or had the need to do something like this. I'm thinking I'll order it and put in after the holidays.

 

[lindnova]

Let us know how it works. I have a 10 yr old Heatmor 200 also with exactly the same characteristics you have. I get the terrible racket of boiling in the door - the noise is steam bubbles burping or more like hammering up out of the top hose.

I burn mostly dry wood, so a slower fan does sound like it would work better.

 

[cantoo]

I thought of this thread while I was loading my owb today. Fan was on when I opened the door to reload. I had a long rod with a 3x8" chunk of flat steel on the end of it. I reach back and pull all the coals to the door. Had the door open while I put a bunch of bone dry ash in it. Shut the door and turned the fan back on. 10 minutes later I opened the door and the fire was going like crazy from the fan. Another 5 minutes and I'm sure the blower would shut off dropping the damper door and smothering the fire. I'm sure it would use much less wood if the fan just ran for 5-10 minutes and the damper stayed open until the temp kicked it off. I might have to do some thinking on this.

 

[Derrick Sawyer]

From my understanding the boiling noise in the door is air in the system, is the bladder working and has some water in it? I heard the channels inside the door need cleaning once in a while and the hoses replaced too. I have the 400 and has 2x150cfm fans, but right now im not heating much space i disconnected the rear fan and just use the front, similar to the 200. I wouldn't want to lower the cfm too much or it can't open the flapper, now you could try getting fan for the 100 model that is 75cfm, but i think that is not root cause, and that maybe the passages need cleaning, and make sure the circulator pump is on high if you have the grundfos. Also your wood water content may be so low that it burns very fast, mix in less seasoned wood and see what happens. Also do you get your water analyzed every year? Add only softened filtered water and not hard water? And add the water treatment gallon as suggested?

 

[cumminstinkerer]

@2012outdoorsman check out my thread, my homemade improved owb, I've been working on the current setup for the past four months and got her dialed in pretty darn good, best thing I've done is the added baffle system and the secondary air injection, I played around trying to get mine to go natural draft but just doesn't work, my dads hardy is an induced unit too but have tried it natural when power goes out, its a total dud, wont hardly burn and never gets warmed up, not enough chimney for any kind of draft. I've played some with variable fan speed and it may help but I think a baffle and some preheated secondary air would help ya way more.