Forced draft?

[Pete33Vt]

I wasn't sure where to put this question. Since I am adding a blower to my rig I guess heres good.
My question is for those of you who have forced draft and are not using the factory grates how did you plumb it up to your rig.?
I know I want to go into the back of the fire box, actually into the ash pan,
I was just wondering how you did it, and if it works good. I have the blower and a bunch of duct work from an old house. Did you run just one round pipe or did you go from round to a wider duct? And on the end (fire side) did you use a diverter to force the draft up into the bottom of your fire?
I have a pretty good idea of how I want it but just looking for other ideas.

Thanks for the help!!
Pete

[Sugarmaker]

Pete33VT,
I may have some pictures on the web site.
I bought a 550 CFM blower which is what Leader recommends for a 3 x 10. It had a square discharge opening about 5 inches x 5 inches . So I just made a square tube about 2 feet long and cut a square hole in the ash pit portion of the arch. I do not have any diverters or air direction devices. I do have a damper in the square tube that can be used, but usually this is wide open.
I did pit a wire mesh cover over the entry to the blower to avoid something/some one getting in there while it is running.

I also installed a 2 speed switch for high and low speed.

This works good and is not real fancy. We are drawing air from the evaporator room to feed this.

I pit the wiring for the fan under the concrete and added a receptacle at this point under the evaporator also.
Regards,
Chris

[brookledge]

Chris
You may find that a reostat switch works better that way you have any speed you like. Try the two speed first and if it blows too much out while on low and feeding the fire then get a reostat.
With mine I made a mark on the dial for the low speed and the high speed. I have a 3X12 from the factory and if I run the blower as fast as possible then it is too much and sends smoke out the seams even though it is fully bricked. And I have noticed even if I do run it wide open I don't see any faster boiling rate only higher stack temp.
Keith

[Father & Son]

I made mine as simple as possible. I bought 2 pieces of flat metal (the same kind if metal duct work is made of) cut and bent it to fit the blower and widened it out to cover the entire back of the ash pit. Took a 2" hole saw and cut out the back panel leaving uneven edges hoping it would create a more turbulant flow and just pop riveted it to the evaporator. Wired it to a reostat as to not blow ash out through the doors. The size of the blower (in cfm's) depends on the evaporator and stack size. I think there was a previous post about blowers with the formula to figure needed cfm's. The blower made a difference in the boil and also compensated for wood the wasn't completely dry. Good luck!

Jim

[Father & Son]

Here's the post from sweetwoodmaple I was talking about to figure out what size blower is needed

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sweetwoodmaple
Maple Enthusiast

Joined: 19 Feb 2005
Posts: 521
Location: Mercer, PA
Posted: Fri Feb 24, 2006 5:43 pm Post subject:

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http://www.grainger.com/Grainger/wwg/itemDetailsRender.shtml?xi=xi&ItemId=1611630891&ccitem=

4C447 is the dayton blower I put on my 2 x 6. Best bang for the buck ($70) and ran my evaporator very well at almost full speed. I arrived at about 3 cfm per square inch of stack area is a good rule of thumb. (Brandon- I believe this is the one that is on your wood saver too).

I went through several iterations with my blower. The thing you have to be careful with is the amount of pressure (expressed in inches of water) that the fan can generate. The ones with low HP vs. flow rate usually cannot generate much pressure. You need a few tenths of water pressure to adequately push air through the ash pit.

Good luck.

1st generation sugarmaker
325 taps on vac in 2006, 10 buckets
3 x 10 D&G drop flue wood fired
16' x 16' sugarhouse with 10' x 12' woodshed

www.sweetwoodmaple.com
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The formula to figure stack area is pi x radius squared, pi = 3.1416, so the area of my 7" stack worked out like this

3.1416 x 3.5 x 3.5 = 38.48 square inches

38.48 square inches x 3 cfm/square inch = 115.44 cfm's

Correct me if my math is wrong but this gives you a way to figure what size blower you need.
I bought a 265 cfm blower just to give me some flexability for later improvements.

Jim

[Pete33Vt]

Jim, thanks for the info. I really hate math but I think I can get it figured out with that formula. So know I need to get my tape measure out and measure my stack then go from there. Its a new rig to me so I am not sure of the size off hand.
Thanks again.
Pete