Killed the draft fan on my 4400 Woodmaster- results so far.

[Butch(OH)]

This started on another thread I didn't want to hi-jack but I was prompted to try my 4400 without the draft fan.
A few facts are I have always suspected that the the Woodmaster air intake system was designed for wet and snow covered rounds as big as one can lift but we burn nothing but 3 year old splits that are stored under cover. Figuring out what exactly it is doing has been difficult since we go from the hi 30s over the weekend to this morning 7 degrees, typical Ohio winter plus the wife doing 30 loads of clothes and fooling with the 'stat. All I know at this point is we are definitely burning less wood, I suspect that given same circumstances, a LOT less but I am not ready to make that statement. A few observations are the stove smokes more than it did before. The build up inside may need to be burned out occasionally with the fan (which is now on a switch). We also have to relearn how we roll and fool with the coals and ashes as the thing burns differently. By that I mean it now seems to burn more completely towards the door before burning what is in the back.

I think ideally a two stage inlet program would be the ticket where when the temp drops to a set point the draft door opens. Then if it drops a few more degrees the fan runs long enough to bring it back to say the cut in point and then shuts off.
We have never varied much from 160 cut in to 170 cut off and by "two stage" I mean something like this
160- draft door opens 170- draft door closes
150 fan cuts in 160 fan cuts out
Not sure if the ETC has the capabilities or if I would need something else to control the fan? Really stretching my electronics abilities here. I also though about a timer on the fan so that it cuts in with the draft door and runs for X minutes before shutting down?

I will add as facts present themselves.

Butch

 

[Stihl310]

Do you by chance know how large the air intake is on yours? I've tried running mine minus the blower once, but the opening wasn't large enough to supply the necessary air. I'd be interested in seeing what results I could get with mine as well.

 

[Butch(OH)]

Opening is about 3x12. I have two extra sections of pipe on the chimney that no doubt makes a difference too.
View attachment 271115

 

[NC4AB]

Butch -

The RANCO two stage thermostat will allow you to program the the draft door and the fan the way you want. I have been running my Hardy H2 just as you described for the past 6 years and tracking the water temperature, damper position and fan status with a data logging program, just about the only time the fan kicks in is when someone takes a long hot shower.

 

[H-Ranch]

Thanks for the info Butch! I think I'll try to add a link to my original post so this pops up there too. With all the variables you had it's not quite a concrete case, but I'm interested in hearing more of the facts with a longer test period.

 

[Steve NW WI]

I also though about a timer on the fan so that it cuts in with the draft door and runs for X minutes before shutting down?

I will add as facts present themselves.

Butch

I'm no OWB expert, but I like that idea. Use the fan to get the fire going good again after a smolder period, then let the natural draw take it from there.

Have you watched it enough to get an idea how long it takes to go from cut in to cut out with natural vs forced draft?

 

[Stihl310]

I'm no OWB expert, but I like that idea. Use the fan to get the fire going good again after a smolder period, then let the natural draw take it from there.

Have you watched it enough to get an idea how long it takes to go from cut in to cut out with natural vs forced draft?

I'm going to try exactly this, I've got a timer relay at home, I'll pull wires back to my control box and place the fan on a timer. When it calls for heat I'm going to charge the fire for a predetermined time, then kill the fan and let natural draft take over.

 

[Butch(OH)]

Well almost two weeks into it now and we are definately saving wood. Seems like the time we save the most is when the firebox has mostly burned down. When using only natural draft and when the loop temps drop and the draft door opens over the bed of coals The 4400 wil maintain temp for a very long time while the coals burn and turn to ash. I had suspected that at this point the draft fan was forcing so much air in the firebox that could not be used for combustion that it was actualy cooling the fire box which seems to be the case. Outside temps are still all over the place, been zero and almost 50 here in the last week. My best guess at this time is 25-30% less wood to do same work. Heating my 1945 1 1/2 story 3 BR home and my 24x22 work shop plus domestic for 4 people we are burning about 1/2 to 2/3 of a firebox full per day of very dry split wood most of which is Sycamore and Ash.
I did have to run the blower fan once over the weekend for one cycle to burn the chimney out, nice spark show. We have much more crud building inside the fire box. Have not played with the running temps yet but past experiance tells me that if I raise it that it will reduce build up inside.

Probably wont mess with it until next summer but I think the ultimate program for my OWB will be the additon of another aquastat, probably digital to control the draft blower seperate of the draft door. Studying the actions of my unit so far I would program it so the fan would run if the loop temps drop 5 degrees lower than the door opening set point and shut off when it reaches it.