Fault finding for AM2 exam

[markneilbarnett]

Hey, fellas does anyone have any resources regarding fault finding. Unfortunately for me i failed the AM2 due to lack of knowledge on this particular subject. Its just so difficult to find a tried and tested method. I can't believe it's all guess work. All you get issued for the exam is a low resistance ohm meter

 

[Richard Burns]

You are using a mixture of visual observation, continuity testing and deduction.
You will be provided with a fault description.
e.g.:
light not working: this must be a disconnection on line or neutral, so test line continuity from supply to switch, across switch, from switch to lamp. test neutral continuity from supply to lamp. Where there is no continuity is the fault location.

RCD trips when light turned on: this is a connection from a live conductor to earth. test continuity between line and earth, break down the circuit until there is only one section that has continuity line to earth, this is the location of the fault.

MCB trips but RCD does not: this must be a short circuit line to neutral. Test continuity between line and neutral with no loads connected, break down the circuit until there is only one section that has continuity line to neutral, this is the location of the fault.

motor runs unevenly: this is (in the test) a phase lost. Test continuity from end to end of each phase the one that has not got continuity is the one that has the fault.

 

[gazdkw82]

Are you assessed during the entire section of fault finding or just given the faults and asked to find the faults in a space of time?

The difference between the 2 is the need to follow the sequence of tests no matter what the symtons of the fault

 

[markneilbarnett]

You are given the symtoms then asked to identify the type of fault,then find it's location then suggest the means to remedy the fault. You have to be as quick as you can because it's timed. You have 7 faults and you need to be 100% accurate on at least 5

 

[markneilbarnett]

You only have a low resistance ohm meter and the installion is de energized

 

[Richard Burns]

You would be assessed to at least some extent during the fault finding but there is no prescribed sequence of tests for this type of work.
You would be working out what type of fault must be present from the description of the fault. If there are options then do a preliminary test to confirm your initial diagnosis. e.g. is the fault on line or neutral, test all the line for the fault, if it is found then you can narrow down on line and ignore neutral. For the test you know there is only one fault, so there are no false bypaths to confuse.
The fault will be a simple wiring fault that may be visually observable, say on reversed polarity the wrong colour cable in the terminal, for a disconnection a loose cable not terminated.