I've come across a faulty kiln (pottery oven) and since the wiring diagram seemed simple enough I decided to try to find the fault myself. However I'm dumbstruck by a strange behavior of a lamp.
The oven is a powered by three phase power (but only use two phases, as evident in the diagram.) The two heating elements are controlled by a digital controller (the box to the right in the diagram) with a 7-pin connector. The controller has a switch that breaks the power (the L1 line) to the controller itself.
Looking at this diagram, it seems obvious to me that the lamp should light up whenever you connect the oven to the power outlet (given that the fuse "F0" is intact of course, which it is.) I mean, the lamp is in parallell with the controller so the voltage across it should be constant. However, in reality the lamp behaves like this:
- When the controller is disconnected, the lamp only flickers very dimly.
- When the controller is connected, and the switch is closed, the lamp lights up at full power. When the switch is open, the lamp is off completely.
What is going on here, shouldn't the voltage across the lamp be constant?