Basic principles
In a healthy state, any basic circuit that has a load and energy source has circuit paths.
Electrical problems can be classified under two broad types:
1. A connection does not exist where it should. This is an open circuit fault and can be detected using a continuity tester
2. A connection exists where none should. This is called a short-circuit fault and can lead to excessive current accompanied by mechanical forces and heating of circuit conductors. Such fault happen due to insulation failures and can be detected using insulation testing instruments.
While troubleshooting, the following points have to be checked:
- Continuity of path (i.e., resistance)
- Electric potential at two points of the path (i.e., voltage)
- Flow of electrons through the path (i.e., current).
To identify a faulty section, below are the guidelines:
- Check the incoming supply voltages first
- Check for voltages at the specific test points in circuit (as per manufacturers test point data sheet)
- Do dead test of circuit for integrity of protection devices and others
- In dead test, check for continuity of circuits, as intended, and check for insulation resistance
- If it’s not possible to perform a dead test, connect the supply to the circuit and do a live test of circuit.
Any electrical circuit can be differentiated in two sections:
- Power circuit
- Control circuit.
Always check the power circuit first. If the power circuit works, then troubleshoot the control circuit.
Power circuit check list:
- Incoming power to circuit and its integrity
- Check for correct functioning of protection devices
- Check visual cable continuity
- Check for any signs of flash or burning smell of devices.
Control circuit check list:
- Control circuit power first
- Check for proper functioning of relays, timers, and switches
- Check visual cable continuity
- Check for wire interconnections and terminal connections of circuit
- Check logical operational sequence of contactor switching
- Check for timer duration settings.
