DIY forced draft grate?

[MarkL]

Hi, I have the steel v-shaped grate that came with my Leader half pint arch. I've mounted a fan on the firebox below the stoking door to increase air turbulence.

Would it be worth the effort to drill a bunch of holes in the grate to allow more air flow to the wood? Should I flip the grate so the v points up, too? What about stacking some bricks in the ash area under the grate to direct the air up under the grate?

Any other suggestions to tweak this system to increase boil rate?

[Cjadamec]

The open end of the V grate should be on facing up.

fire
wood
vvvvvv
air

The open V catches ash from the fire and insulates the grates helping to protect them from warping. They also collect the coals and prevent them from falling down into and blocking your forced draft air space.

The open spaces between the V's is more than enough area for your draft air to come up thru the fire so you don't need to drill any holes.

In an air tight arch the draft air has no place to go except up thru the fire and out the stack. You don't need to direct the air up into the fire but you may want to make a tunnel for the air so that it exiting the tunnel under the middle of your grate. This will help put more air into the middle of the fire.

You should be seeing around 15 gph with your set up as long as you are using good dry wood, have the wood split small, are feeding the fire regularly, and have a preheater setup. Your AUF fan should be in the 200CFM size range, or bigger with either speed control or air diverter setup. If you find that you are getting a very hot fire but are getting heavy and or black smoke out the stack you will need to consider looking into adding air over your fire (AOF).

[MarkL]

Thanks for that suggestion. I’ll give it a try.

My wood is dry, I do small stokes every 5 to 7 minutes. I have never hit 15 gallons per hour, by my estimate the best is around 5 to 8 which is very disappointing considering what this pan is supposed to do.


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[ecolbeck]

If you have a half pint with standard pan I would think that you would top out at 9 gph. Although I’ve not used a half pint (I have used a 2x3 with blower) I don’t think 15 gph is realistic.

[Cjadamec]

If you have a half pint with standard pan I would think that you would top out at 9 gph. Although I’ve not used a half pint (I have used a 2x3 with blower) I don’t think 15 gph is realistic.

He has the Smokey Lake drop flue hybrid pan for hiss half pint. That pan should exceed the output of a standard flat pan by a good amount.

What size blower fan are you trying to use for the AUF?
Also how are you adding sap and are you preheating the sap?

[MarkL]

I believe the blower is 50 CFM. I have a float box on the side that lets in the sap, there is a small preheat channel in the back of the Smoky Lake pan. Do I need a stronger blower?

I should be boiling tomorrow - tonight I am going to rig up some ducting under the grate to direct the air up at the fire and see how that goes.

Mark

[ecolbeck]

I completely missed the part about the SL pan, whoops. I think 50 cfm is too little.

[Cjadamec]

You need a bigger blower. I would say at least 200CFM. Don't bother with ducting under the grate you really just need more air if all your current blower is doing is 50cfm.

You don't want to blow at the fire you want to blow air under the fire and have it rise up thru the fire. AUF is about saturating the fire with oxygen with high volume low pressure air.

[MarkL]

Thanks, hopefully I can get a new fan installed by Friday or Saturday.