Wire diagram help?

[Gting]

I have been looking through the stickys for a couple hours now, and used the search engine, but I am having a hell of a time finding a 110v wire diagram for a PID and thermocouple. I got an old kiln 14.5 deep by 12 square with a top opening lid. It was used for small pottery and crafts, but before that it was used in a lab. Its current dial is a high to low and has 2000 as a max temp. Plugged it in and it seems to work fine. I just want it to be more accurate for heat treating simple carbon steels.

 

[Stacy E. Apelt - Bladesmith]

I have posted the directions several times. The stickies has a section on PID and ovens. The one for converting a toaster oven is pretty much the same as for converting a kiln. What you do is make a controller and plug in the device being controlled

Here is what you do:
Don't modify anything on the existing kilns wiring or controls!
Drill a hole and mount the new TC in the kiln. In the top is the easiest place.
Hook up the PID, SSR, heat sink, and TC as normal per the many diagrams available. The place where the heating coil would be is where the kiln will fit in the circuit.
Wire the output of the SSR to a 115VAC socket.
Use a pig-tail power cord to supply the 115VAC to the PID/SSR.
Plug the kiln into the socket.
Turn the kiln ON and set to HI.( nothing should happen)
Turn on the PID and set to the desired temperature and push RUN.

If that isn't clear, let me know and I'll draw a wiring diagram.

 

[Stacy E. Apelt - Bladesmith]

I did a schematic for you anyway.

 

[Gting]

Thanks for the reply Stacy. What gauge wire would you use?

 

[Stacy E. Apelt - Bladesmith]

Without knowing the draw of your kiln, it is hard to be exact, but on a device that will run long hours at fairly high current, I would use a 12 gauge cord for the power cord and 12 gauge wiring to the SSR and socket. The wiring to the PID only needs to be 18 gauge, but I would probably use 16 gauge.

BTW, I made that drawing simplified. I would add a switch in the line from the PID to SSR to have a master shut off switch for the kiln. That switch can be a simple 1 amp SPST. The main power switch on the incoming line needs to be a power switch capable of taking 125% of the kiln amperage. While a SPST switch would be OK, I would probably use a 30 amp double pole switch like this - http://www.homedepot.com/p/Leviton-...00356941?cm_sp=BazVoice-_-RLP-_-100356941-_-x

Other additions that are nice are lights to indicate "main power on" and "heating coils on". Don't forget that the SSR will need to be properly mounted on a heat sink. A small cooling fan isn't a bad idea either.