The element turns out to work perfectly. And it heats the oven far faster than what you would want, but the PID controller takes care of that. The controller will turn the current on and off to the element to control the rate of climb to whatever you want. And the 3300 Watt element can easily heat the oven up to the max 2200 degree F. I had hoped for. On my first use I slowly ( over 8 hours) brought up the temp in timed stages to 1200 F. and then let it cool down naturally. 8 hours later it was still 120 F inside (shop was 60 F.). Inspection showed there to be do damage to the refractory or anything else.
As you can see in the photo (element is just turning on) the element heats up faster where the coils are closer together. It turns a uniform color after about 10 seconds. I sorted this out by stretching the hot areas out a bit more. After getting hot the wire is much stiffer and I suspect more brittle.
The second go I did the same thing only I took it up to 2000 F. over 10 hours and held it there for 3 hours. After cooling down everything still looked good.
I made a drip pan for burning out wax. The grate is S.S. But the pan is mild steel. I will make a stainless tray when the material arrives. The photo of the pan shows two 4 inch flasks and one 3.5” flask. The drip pan is elevated above the floor by .5”. I have a long heavy duty spatula that I can remove the pan with when needed.
I have been doing some early tests burning 3D resin printed parts just lying on the drip tray and it is extremely stinky. Its the kind of stink that hangs in the air for days. The hood works great collecting the smoke and directing it to the overhead hood vent but the slightest breeze will let some smoke escape. My shop can be drafty so I plan to add a curtain made of fire prof felt that will attach to the back and sides of the hood with magnets.
“Abby” in a previous post suggested I needed a much larger vent hole in the top. I think I will start with a bit larger (tan planed) top vent hole and air provided by a controllable aquarium air pump to a couple of holes in the kiln's floor. After I put my furnace through a few test runs I will let you all know what I finally end up with.
My original budget was $600 and I came close at $660. The hood, the drip pan and a spare element put me over the original budget. I also plan to protect the floor with a “kiln shelf” and expect to spend another $20 there. I don't know what it will cost to operate but my area of Washington State enjoys one of the lowest electrical rates in the country. The Hydro-power dam is only seven miles away.
To avoid electric shock I plan to add a micro switch that interrupts the signal to the relay if the door is open. And I plan on making myself a ceramic coffee cup and a beer mug.