I have built a tube furnace like the one in this video: https://youtu.be/YRZ7aQlqetE
The person in the video is able to reach 1100 C using an AC power supply. In summary, the furnace was made by wrapping an alumina tube (30 mm diameter) with ~7.6 meters of 22 gauge nichrome 80 wire, coating the wire in Dap furnace sealant, then finally wrapping the whole thing in two layers of alumina blanket. The furnace is controlled by an Auber Instruments SYL-2342P PID controller and a Holdwell 45GG20AF 2 pole 40 amp 120V coil contactor. There is a K-type thermocouple inserted into the tube. The diagram below depicts the wiring of the system, minus the alarms and the fuse.
The controller is programmable, and I programmed it like this:
- C01-> 50 (starting temp in Farenheight)
- t01-> 20 (ramp time in minutes)
- C02-> 1832 (set temperature)
- t02-> 15 (soak time)
- C03-> 1832
- t02-> -121 (stop)
Here's the problem: when I run this program, the furnace will hear up until about 1325 F then the temperature increase rate will slow dramatically until the controller stops the program. I am not sure if this is a problem with the furnace or the controller. Any help would be appreciated.