Wednesday, December 17, 2008

Heat Treat Furnace Thermocouple Installation

The furnace is complete except for the thermocouple, which makes the controller into a very advanced thermostat. Without it the controller is blind and cannot regulate the temperature. What makes this sensor special is that it can measure temperature up to 2,300 degrees F, or the so-called cone-6 temp for kilns.

Most other devices would have long since melted or burned to a crisp.

The thermocouple works on a principal called the Seeback effect. The junction of two different metals creates a temperature-variable voltage. Each rod is a different alloy of some metal , and are welded together at the tip. A set of double-holed ceramic spacers ensures a seal on the kiln as well as keeps the rods separated.

I had to shorten the thermocouple to correctly fit my furnace. Here it is attached to the ceramic mounting junction.

I drilled a 1/2" hole between the furnace element studs. The studs and related hardware are all stainless steel. I have a rudimentary but cheap method of isolatingthe intense heat from the terminals from the feeder wire to the controller - I used about 3 feet of 14-gauge solid copper wire from a length of romex I found outside on the ground, and made radiator spirals.

I attached the thermocouple wire provided to the mounting block and ran it back to the controller.

The tip protuding into the oven interior by 2". Minimum according to directions is 1.5".

With the controller feed hooked up, and the protective cover in place. When energized these coils will be hot and live with 250V AC.

The completed furnace.

With the door open. I have run it to reach a temperature of 100 degrees. It works well, and regulates. The controller can be set into learning mode to figure out the system parameters and be quicker to ramp up and prevent overshoot.

Now just some things that need to be heat treated :)


John Terry said...
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John Terry said...
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John Terry said...
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