Hey Everyone,

I'm working on making a ceramics kiln and have a question regarding which type of connector I should use for connecting the copper power lead to the heating element. I have already designed most of the structural portions of the kiln out of a steel frame, 3 inch low density fire brick, and a vent port for any harmful gases. Additionally, I have zero volt switching and current regulation for heat and zone control using three elements. However, I just realized as I was assembling a BOM for the project that although I have confidence in the structure and design of the kiln and electronics driving it, I didn't know how to make the connection in question. I know there is little to no concern of ohmic heating in the cable given the gauge and the low resistance, so my concern is more heat leaking onto the copper power rail from the kanthal element since this will be operating up to 2200F.

The plan is to connect the copper to the element right at the boundary of the interior kiln wall: read: the copper will go ~2.75" through the fire brick --> crimped connection to heating element --> kanthal heating element on interior of kiln. Would there be any issue with doing it this way? Should I just wrap a good portion of the power cable in a fiberglass insulating sleeve for safety? Do they make any specific types of connectors for this application?

Any help you guys can provide would be greatly appreciated since I can't seem to find any definitive info online regarding the safest way to do this. I've got overtemp safeguards in place now if too much heat does exit via this path and I'll be around the unit during all operational runs. However, with that said, I'd still like to make this connection in the most secure and safe way possible.

Best Regards,
Mezz

 

482F is the highest temperature insulation I can find in the NEC code book. I assume you are considering insulation failure on the copper wire due to conducted heat. The connections I have seen include spot welding, a slide-on connector like a 1/4 inch spade connector, and a nut and bolt connection.

There is no rule that says you can't use a copper rod to get through the kiln wall and then connect a standard, insulated, copper wire to the copper rod.

I'm going to get kind of vague now. You need a distance, a length of conductor which loses a lot of heat. This can be managed in several ways which depend mostly on your imagination. The hitch is making it safe for a copper rod (or wire) to radiate heat without being a shock hazard or a fire hazard. The usual method is to enclose all conductors and/or connections in a fire proof metal box. The apparent difficulty there is in getting heat to radiate in a closed space. Your imagination will be required to design a space through which air can move without a path for flames to escape or for a person to touch the energized conductor.

Have I merely defined what you already knew or pointed your thoughts toward ways to fix the problem?

 

The first kiln for 1000C use I built some 40 years ago and many after it, and repair similar rather regularly. My advice - never make an any kind of connector near the hot zone. After year of exploitation the place where kanthal (or nichrom) will burn off, will be the zone between cabling and owen really hot zone entrance. That is well checked, rechecked and assessed that there is no other stable enough solution as only to wind a kanthal wire like litcendrath (litz-wire), or better, specially for smaller diameters even double so the entrance section of kanthal is double or four-fold folded (spiralling alias close contact is very essential) gives lesser temperature for this part and then the next brake point is the most hottest point of owen - what is just imminent. So, make a litcendrath (use drill machine plus screwspieles), in the wire-end make a non-interrupted loop where put the screw of 8 mm or better 10 mm. You not need a better schtecker there.