Vent fan for downdraft Kiln vent

[MissyLee5]

Hello all! 

I am building my own Kiln venting system. I've got everything I need except for the inline vent. Based on other vent systems I need around 140 cfm for the fan, but for the life of me I cannot find one with a reasonable price. I've been searching for 2 weeks and keep coming up empty.

There are plenty of 100 cfm metal inline duct fans for around $20, and plenty of 190+ cfm (although these seem to have plastic housing and are shaped differently, marketed for Grow tent ventilation) for $40-60, but I can't find anything between the two, aside from one or two models that are $100-200 which I'm just not willing to pay. 

My kiln is 3.2 cubic feet (Skutt KM 822). I'm going with a 3" duct, but will use a reducer so I can use a 4" fan as these seem more readily available than 3" fans. I'm purchasing the plenum cup used with the skutt envirovent 2 rather than trying to build one that can move with the kiln bottom when it expands/contracts during firing.

It's starting to seem like my only options are to either get the 100 cfm and hope it's got enough power, or get a 190+ cfm with an adjustable speed controller. I've got no clue how big of a difference 100 cfm is to 140 in this application. Would 100 cfm be enough to pull the fumes out of a kiln this size? Or even better, does anyone know of a reasonably priced fan around 140 cfm? Any recommendations are helpful. 

[neilestrick]

THIS is what you need. It's what's used in most of the commercial vent systems. Use a 3" for the intake, 4" for the out.

6 hours ago, MissyLee5 said:

I'm purchasing the plenum cup used with the skutt envirovent 2 rather than trying to build one that can move with the kiln bottom when it expands/contracts during firing.

You can also use a box/cup that screws to the side of the kiln, or rig up something that connects to the kiln stand.

[MissyLee5]

@neilestrick thank you! This will be perfect as my existing vent in the wall is 4" and I'll be using 3" ducting. Costs a bit more than what I was hoping for but since it's what's used commercially I'm not opposed to spending a bit more. Still a huge savings over buying the full venting system!

I thought about doing something like that for the cup, but I'll probably stick with buying the plenum cup part for simplicity & time sake, unless I can come up with something very easy & cheap. Thanks again! 

 

Edited to say: The outlet height & width of that blower are confusing me. Based on the specs, it seems the outlet is less than 4", so I'm wondering how it will cover the 4" hole in the wall venting to the outside? I've got a pre cut circular 4" hole in the wall.  

 

Second edit: I just spoke with Grainger. The outlet dimensions are 4 5/8" by 3 1/2", so I would need to find a way to modify my existing wall cutout for the outside vent, or find some type of adapter. As is, if I try to hook it up it won't completely cover the cutout. I'll see what I can come up with. 

Edited January 11, 2022 by MissyLee5
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[AllieRenee]

Hi! What motor did you end up going with? I'm thinking of doing the same thing - using the plenum cup from Skutt - but then sourcing the rest of the material. Would love to hear how this ended up going!

[neilestrick]

4 hours ago, AllieRenee said:

Hi! What motor did you end up going with? I'm thinking of doing the same thing - using the plenum cup from Skutt - but then sourcing the rest of the material. Would love to hear how this ended up going!

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