Tips for Intermittent Fault Finding

[Dartlec]

Things the don't look plugged in, like outside lights or internal stuff in the form of lights, hand dryers, etc.

Some places are bad for having years of stupid modifications, and from other sparks' comments pubs seem to be #1 for that.

Or switch the ring MCB off and get the bar folks to check everything to see what has stopped working?

Not just pubs - there have been at least two properties in the last year with a random breaker with cable attached to it that I turned off and nothing has been spotted not working when I've gone back weeks or months later. One of them was even labelled "unknown" at the CU years ago so if the installer didn't know then I don't have much hope of finding it!

 

[UNG]

IMO faultfinding is an art and a skill that is developed over many years and a good memory of past faults found on previous jobs helps a lot. After that it is down to having a good knowledge of the test equipment you have and how best to apply it to get the results you need to locate the fault
Over the years I have built up an assortment of test equipment that is mainly used for faultfinding, I find good cable tracers that will work on both open and closed circuits are a very useful piece of kit to have (can be useful to find plugged in appliances, cable faults or identify circuit cables) after that a logging multimeter with a current clamp is useful for those faults that happen when your at home and in bed other bits I've added over the years are a non contact thermometer, power logger, thermal imager and a scopemeter to list a few bits

In recent years on of the most common intermittent faults I've had is the auto defrost fridge / freezer with the failed heating element, they can trip between 12 to 72 hours after the RCD is reset so it is difficult to find without accessing the element for a direct test

 

[Marvo]

With a lot of intermittant faults you're more likely to find them by visual inspection and a bit of experience than just by using a tester. There's many faults a tester won't help whatsoever in locating.