Outdoor Wood Furnace Info

All-Purpose OWF Discussions => General Outdoor Furnace Discussion => Topic started by: harley on February 09, 2014, 10:03:54 AM

Title: Forced draft over fire or fan under the fire
Post by: harley on February 09, 2014, 10:03:54 AM
It would seem to me that if you have a ash or hot coal build up in bottom of the fire box it would be hard for the fan to force air up through the grates  from the bottom of the fire box so over the top of the ash would burn better and hotter. 
Title: Re: Forced draft over fire or fan under the fire
Post by: Scott7m on February 09, 2014, 10:08:11 AM
It would seem to me that if you have a ash or hot coal build up in bottom of the fire box it would be hard for the fan to force air up through the grates  from the bottom of the fire box so over the top of the ash would burn better and hotter.

nope, opposite is true

Unless u simply let ur ash get packed in there and never stir it

When it comes up through the coal bed it gets hot and intensifies the burn making it burn hotter and cleaner


Thats not to say that a forced fan through the door doesnt Work because it does, but there is an advantage to it coming up through the coals...
Title: Re: Forced draft over fire or fan under the fire
Post by: mtoll on February 09, 2014, 10:15:32 AM
So it better to stir the top draft it little more often
Title: Re: Forced draft over fire or fan under the fire
Post by: Scott7m on February 09, 2014, 10:19:57 AM
So it better to stir the top draft it little more often

yea with any stove once your coal bed gets fairly deep its good to give it a quick stir once a day. 

One advantage top draft has is that if folks get lazy and dont keep ash loosened up that it always burns the same.  For example if u have below grates air coming in and only have a 6 Inch spot in grate thats open all air will wanna come up through there, either will work and work well though
Title: Re: Forced draft over fire or fan under the fire
Post by: racnruss on February 10, 2014, 11:28:16 AM
some stoves have both!
Title: Re: Forced draft over fire or fan under the fire
Post by: Marktk on February 11, 2014, 11:25:08 AM
Have both would be the ideal setup im assuming? Could a guy add over the fire air easily enouhg?
Title: Re: Forced draft over fire or fan under the fire
Post by: racnruss on February 11, 2014, 12:30:32 PM
With some fabricating skills, anything is possible.  Heatmaster has some models with over and under air.  In your case, maybe some sort of scoop in the back of the firebox that extends down into ash area to catch some of the air blowing in and directing it up into back of firebox above the fire.