Holes in kiln lid needed?

[deborah6]

I just bought a used (preowned as they say in the car world) kiln. It had previously used a Skutt Enviro Vent on the bottom (so holes are drilled there), but there are no holes in the lid. I plan to also use a Skutt Vent, should I drill hole in the lid now?

[Hulk]

noHi Deborah!

My understanding is that hole(s) in the lid are required if/when the kiln is fairly airtight - if the kiln has enough little leaks, extra holes wouldn't be necessary.

Try running a really bright light inside the kiln (when the room is dark ...at room temp, of course) - see any twinkles?

My used Skutt did not come with an Enviro Vent, however, I want direct venting, hence put together a duct box, inline fan, etc. From there, I did add a small hole in the lid, as the other leaks are near the bottom of the kiln.

A simple test for the inlet: with the fan on, hold a lighter/match flame over the hole; is the flame drawn in (careful, easy to singe y'finger here!)? When the kiln is at temp, is the system still pulling through the hole (when it really matters)?

My dyi system didn't pull hard enough, first trial, so I added another hole in the bottom (where the duct box meets up); now it working better.

[neilestrick]

Skutt says to put a hole in the lid. L&L says it's not necessary because kilns aren't that tight. I would first try firing without lid holes and see how it goes. If it's not venting fumes well enough, add a hole.

[Bill Kielb]

Since I have the equipment to measure hundredths of an inch of pressure and I have measured five different kilns  and redesigned a replacement for a failed factory built system, my opinion is I have not seen a kiln where the lid fit alone was not effectively as wide as the Grand Canyon for leaks of tenths of an inch of suction pressure let alone hundredths.

couple that with section seams and thermocouple penetration and kilns  are  likely pretty leaky.

only my experience though - so take it for what it’s worth. I do not drill holes in the top of my kilns.

here is a link to a redesign and retrofit. Suction is adjustable and the vent above removes the wax fumes pretty effectively from 400 - 800 degrees.

 

 

 

[Hulk]

Nice work Bill!

Did you make the duct boxes, or did you re-use existing? If you fabricated them, readers might like to see some detail - I'm interested, however, already went with typical rectangle that fits up against the bottom.

Also curious what model and make of fan.

[Bill Kielb]

11 hours ago, Hulk said:

Nice work Bill!

Did you make the duct boxes, or did you re-use existing? If you fabricated them, readers might like to see some detail - I'm interested, however, already went with typical rectangle that fits up against the bottom.

Also curious what model and make of fan.

If you are referring to the attachement to the kiln,  they were existing and simple 4”  duct end caps with a hole drilled through the end cap. This entire system was an existing one that had operated for about five years, the end  caps did not contain holes for bypass air and that is what destroyed the exhaust blower that was in place. A tiny amount of 2000 degree air, lots of condensation and a recipe for failure.

I am not sure who installed the previous system, but their intentions likely were fine, just not entirely familiar with why mixing bypass or room air with kiln air is part of these designs. I simply added holes similar to the production models to solve.

everything in the picture is new, so simple 4” duct stuff. Two screws every joint and UL Fm duct tape all seams and joints. Should last them a long time and was intended to be a better replacement for the existing.

fan is a Fantech FR 110. Being axial it really needs to cool itself so th exhaust grill above the kiln  is important as well as ensuring a mix of room air to cool down the hot kiln exhaust.

[Hulk]

Thanks Bill!

My dyi box has openings for room/bypass air with sliding tabs for adjustment. My fan is a cheapie inline, will be lookin' at that Fantech if'n it fails down th' line.