UK AM2 Fault Finding

[Marcusopenshaw]

Hello everyone,
I have my AM2 fault finding resit on Friday and just wondering if anyone has any top tips as I don’t get to do any fault finding at work?
In the AM2 you get 7 faults which can be on these circuits:
1 usually on a data circuit
2 on earth bonding to extraneous parts water pipe and gas pipe
3 lighting circuit with two 2 way switches, one intermediate sw and one light
4 smoke alarm circuit with fuse spur
5 ring main sockets
6 3 phase outside socket with TPN isolator
7 3 phase motor with DOL starter ( really struggling on how I would find a fault on this because I’ve never done one before)
8 s plan with thermostats boilers etc on (again struggling how to find faults on this circuits because I never do them at work)
You can only use a continuity tester to find all faults no insulation resistance test
I know the faults I’m looking for
Open circuit
Short circuit
Reverse polarity
High resistance
But just wondering how you would go about finding the faults especially the motor and s plan circuits.
Thanks Guys

 

[Lucien Nunes]

I cannot stress too highly that the key to faultfinding is having a sound understanding of how something is meant to work when it is working. For example, if you know what is inside a 3-phase motor, you can predict what sort of continuity readings you should get across the outgoing terminals of the starter, and also how the motor would likely behave if one of those terminals was not making a good connection. Of course, you need to have an organised strategy for troubleshooting too, but that is of little account if you can't tell the difference between a normal reading on the meter and an abnormal one.

A useful exercise is to draw a circuit, explain to yourself the function of each conductor and connection and how you would prove each one was sound using the meter, as well as how you would prove there was no short-circuit present. Then, imagine a fault such as a disconnect or short, and identify what points you would need to test between to locate it, and how you would distinguish between that and another fault that caused the same symptom. E.g. draw a 2-way + intermediate lighting circuit, and consider the specific symptoms of a break at L1 of the first switch, then L2, then the common. Then repeat for the other switch. Patterns will begin to emerge that will suggest a sequence of tests with the meter.

Likewise with the heating system, draw the circuit, imagine a fault at each component and connection. It might take hours to go through every permutation but you will have a better understanding of the system in its own right, and all of this you can do with just a pencil and paper. If you can't predict the effect of a particular fault, refresh your knowledge of how the associated component works.

AFAIK the AM2 faults are straightforward and not designed to trip you up, and will all yield to a methodical comparison between how the circuit should be and what the continuity tester tells you is present. Real-world faults can be somewhat different!