What is the best and quickest way to find an earth fault

[sherman0251]

Hi, im an electrician and am wondering what is the best way to locate an earth fault causing an rcd to trip? Are there any tips from good sparks out there who have sussed out quick ways to locate these faults. I kniw it varies on ring finals and lighting circuits but any advice and methods would be appreciated.
Cheers in advance

Ian

 

[PrenticeBoyofDerry]

Firstly take everything off load.
Ramp test RCD
Then IR test circuits.

 

[plugwash]

As PrenticeBoyofDerry says there are various tests you can do that will help locate SOME faults that will cause or contribute to unwanted RCD trips. Another one is to turn on everything on the RCD and put a clamp meter arround the live and neutral (but not the earth) supplying it to measure the "normal" leakage for that circuit.

However you should be aware that sometimes you get intermittent faults that are nearly impossible to find. Sometimes the only viable solution is to split the load across more than one RCD and see which if any of them continue to trip.

 

[bernardgreen]

Also remember the earth fault can be on a circuit that is isolated (MCB off ) and still trip the RCD when there is a load on another circuit which is fault free.

Neutral_Earth_trip

• bernardgreen
• 16 Jan 2011
• 48

 

[ericmark]

I think as with most fault finding it has to be split into two methods.
1) Look for likely faults.
2) Systematically look for faults.
The trick is to know when to switch.

So we look for the common faults first current stuck in toaster, two way switching on stairs lighting, immersion heater, the list goes on.

This means unplugging everything and switching off all FCU's once at that point isolated consumer unit and test insulation resistance there. Fixed filtered sockets are a problem but once certain it is something switched on or plugged in causing the problem again return to the list of normal items the outside light for example.

Items with timers are a real problem frost free freezer, washing machine, PIR controlled lights for example often only real way is long extension lead and power off the other RCD in the house.

I find the PAT tester a real aid the earth leakage reading is very handy you can measure with the item under power so easy. One reason I like my manual PAT tester.