Lid Holes For Downdraft Vents

[Guest]

I looked at the manuals from Skutt, L&L and Orton downdraft systems and I beleive this is a simple DIY project.

 

My kiln is 3 cubic ft with one section. I'll be using a 140 CFM fan to vent to the outside with less than 8' of duct work and high heat hose combined with one 90° turn. There will be a 4"x8" chamber under the kiln to attach the duct where I will have a hole with a slide adjustment similar to L&L to vent this chamber.

 

The only part that I find conflicting in all three manuals is the amount of holes I should drill in the lid

 

Orton reads that I should drill one 1/4" hole

Skutt lists that I should drill two 3/16" holes

L&L says that I should not drill any holes claiming that there is enough air leakage between the lid and each section. Since I only have one section I'm thinking I may discount L&L recommendation.

 

So here's my thinking:

 

I'm going to drill 2 1/8" holes at 10:00 and 2:00 in relation to the lid. This is the hole positions Orton suggests for two holes (Skutt mentions the holes should be at 3:00 and 9:00). If I find I need to step up to 3/16" it should be an easy step.

 

Good Idea? Bad Idea? Any recommendations, advice? Am I missing something? (I'm leaving myself wide open on that one)

 

Thanks in advance

 

 

Sorry, I just realized I posted this in the wrong section.

[neilestrick]

The leaking is primarily from the lid lifting as the bricks heat up and expand. Leakage between sections is minimal. That said, on small kilns the lid won't lift nearly as much as larger kilns. I had to drill holes on my 18" wide L&L kiln because it was just too tight. Start with the two 1/8" holes, you can always go larger. Keep them opposite each other.

[Guest]

Thanks once again Neil

[Marcia Selsor]

When I was teaching at UT Brownsville, the electric kilns were in the classroom 4000 sq. ft ex-motor pool

building. They were Skutts and vented with 3/16 holes in the lid. Never smelled anything from the kilns.

If someone forgot to turn on the venting system , you could smell it.

 

Marcia

[Guest]

Installed and tested the DIY down draft system today, seems ok.

 

When I tested the flow using smoke from a bunched up roll of paper about a third of the smoke was drawn in (I know, very scientific air flow measurement). 

 

I'm guessing this should be enough?  As in this is not a wind tunnel?

[neilestrick]

As long as something it being drawn in it will work. It won't grab all the smoke.

[Guest]

Thanks again Neil