Blower

[backyardsugarer]

How many CFM on a 2 by 8? I am putting one in myself. I found 70, 80 and 140 cfm with adjustable rheostat.

Chris

[RileySugarbush]

I have 200CFM on my 2x6 and could use a bit more.

[Father & Son]

CFM's are calculated on stack size not evaporator size


From a previous post -


(The blower size is based on stack size.

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.)

With a blower that is oversized you can either put it on a rheostat or put a damper in the duct work to adjust your flow.

I now use this blower on a 2x8 with a 10" stack and still have to damper it down.

This formula was posted on here a few years back by someone with more knowledge than me but I have refered to it many times.

Jim

[RileySugarbush]

CFM's are calculated on stack size not evaporator size



Yes, but stack size is based on evaporator size and the size is probably assuming natural draft. With a blower, you can probably get away with smaller stack, which throws the whole equation out of balance! One risk of doing that is it increases the firebox pressure to be a bit higher, increasing the need for an airtight firebox. Don't forget that different blowers have different performance curves, meaning some would have very poor performance wit a little back pressure and some better. Here is what I bought. Discontinued now but there are similar available.

http://www.grainger.com/Grainger/items/4C754

You really need to think of the whole draft flow path. For a 2' wide arch, I would run at least a 200CFM and probably more. If you are going to damp the air flow rate, put the damper on the blower inlet, not the outlet.

[nymapleguy607]

Changing the subject a little
Has anyone ever used a blower off an oil burner before?
Is this even possible
I want to get a blower that can move lots of air at higher pressure
Without spending a fortune
I think some once said you could use these
Thanks

[WESTVIRGINIAMAPLER]

Chris,

I have a 760 CFM blower on my 2x8. Maybe overkill, but it don't boil as fast when I run the blower less than wide open. Higher it runs, the more static pressure it should create.