RCCB tripping when under load problems

[Shurbunkin]

When you did the IR tests did you leave all the cpc's connected to the cu?

No I didnt. I turned all MCBs off. Will try that

 

[Shurbunkin]

Have you got an earth leakage clamp metre?

No I dont

 

[Deleted account]

Check any hard wired appliances like boilers, extractor hoods etc are disconnected as well. Not just switched off.

 

[marconi]

Thank you for the progress report. It satisfies our interest.

 

[Shurbunkin]

IR fault on an adjacent RCD controlled circuit?

I think this may be the case as well. Will need to head over there again and spend a couple of hours testing the rest of the circuits one last time

 

[Octopus]

No I didnt. I turned all MCBs off. Will try that

Its important to do these tests with the CPC's connected or else you won't get a true picture of what is going on.

Thanks for the update.

 

[Octopus]

I think this may be the case as well. Will need to head over there again and spend a couple of hours testing the rest of the circuits one last time

This is when having an earth leakage clamp meter helps - I think they are essential these days.

 

[Shurbunkin]

Check any hard wired appliances like boilers, extractor hoods etc are disconnected as well. Not just switched off.

That's a good idea. Ill isolate the fans, cooker hood and boiler from the circuits and see what happens. That maybe the reason. I find when I fault-find I always look at the worst case and take them apart instead of just looking at the simple possibilities. It wastes a lot of time

 

[Octopus]

I was fault finding a circuit last week because a switch had stopped working - on the switch drop there was no continuity on any of the 3 cores , IR at one end was OK, but at the other end the IR had a dead short N-E.

A new set of shelves had been put up......

A drill had gone through the cable completely!

The end of the cable with the dead short wasn't connected to anything so wouldn't have shown up on any tests .....

Given its a kitchen circuit, has Kev the fitter damaged a cable for you?

 

[SparkyChick]

I'm assuming that the IR tests you've carried out have all been fairly short tests... press the button, get the result kind of affair?

Can you continue the test, maintaining the 500v for a while?

I've had a couple of cases where the test appears to be satisfactory, but if you apply the test voltage for a longer time the charge builds up to a point where it jumps a pinhole in the insulation and the IR momentarily drops. Not so easy to see on digital test gear if there isn't a virtual analogue display, but visible on my Megger's virtual analogue meter in the LCD.

 

[marconi]

I think this may be the case as well. Will need to head over there again and spend a couple of hours testing the rest of the circuits one last time

To help us mull over this problem could you tell us the type of supply and earthing system, the presence and state of EP bonding and provide a picture of the intake and CU innards please?

As Murdoch said, it would be really helpful if you could borrow an earth leakage clamp meter to do some measurements, for example standing leakage for each final circuit, and then total leakage less kitchen FRC, and then finally total leakage for all FCs.

Also could you post some figures for your measurements of IR?

Is all the wiring and are all the wiring accessories on the kitchen ring new? Have there been any water leaks?