RCD tripping issue on ring circuit

[Josh Kav]

First time poster go easy on me.

Got a call out to a job today, got told the RCD was tripping. Even when no appliances plugged in. And so it was intermittently about every 20 mins. Only two ring circuits on the RCD, on one of the rings im getting continuity across line and netural on both legs. Its not taking the MCB out, no fault across the earth.

Tested the RCD for nuisance tripping all passed fine.

Cant get my head around why with a permanent short the MCB wont trip? Going back tomorrow morning for further investigation and feeling as if i should suggest re wire of sockets due to reasonably low IR readings anyway.

Any thoughts would be appreciated.
Cheers

 

[SparkyChick]

Welcome to the forums.

When you say continuity... what kind of readings are you getting Line to Neutral? I'm suspecting they are not shorts but some appliance.

Why do I say that? Because a line/neutral fault won't trip the RCD because even under a direct short, the current flowing in line will be the same as that flowing in neutral and the RCD will quite happily sit there.

What IR readings were you getting?

 

[Josh Kav]

Cant remember the exact values on continuity, but it was a high level of resistance.

There are some kitchen appliances left to be checked, but those are on fused spurs so i suppose a fault could still come back up the netural if only single pole switch.

IR getting >0012 and i know its technically acceptable but its pretty low and makes me feel a bit uneasy.

 

[buzzlightyear]

possible damp .

 

[SparkyChick]

If you're getting continuity but a high resistance, then it's more like to be something plugged in/connected.

The IR reading is that L and N to earth, or L to earth, N to earth, L to N? And is that 1.2Mohms?

 

[Josh Kav]

L and N was 12 Mohms not 1.2 but thats all i can remember of the top of my head right now

 

[MJPD29]

Is there any chance there's an exterior light wired out the back of one of the sockets that might have damp in it? I've seen this happen many times

 

[buzzlightyear]

Is there any chance there's an exterior light wired out the back of one of the sockets that might have damp in it? I've seen this happen many times

damp post #4

 

[MJPD29]

I only ever read the post buzz, never the comments lol. For all I know I could constantly be repeating what others say

damp post #4

 

[dinger809]

What is the IR neutral to earth?

 

[123]

First time poster go easy on me.

Got a call out to a job today, got told the RCD was tripping. Even when no appliances plugged in. And so it was intermittently about every 20 mins. Only two ring circuits on the RCD, on one of the rings im getting continuity across line and netural on both legs. Its not taking the MCB out, no fault across the earth.

Tested the RCD for nuisance tripping all passed fine.

Cant get my head around why with a permanent short the MCB wont trip? Going back tomorrow morning for further investigation and feeling as if i should suggest re wire of sockets due to reasonably low IR readings anyway.

Any thoughts would be appreciated.
Cheers

Find the fault, fix the fault. Don't just go rewiring a circuit because there is a fault on it.
As the fault is still not found it could be literally anything, faulty appliance, central heating pump, damp, damaged cable and many more. Find where the fault is first, then come up with the solution.

 

[Wilko]

Hi Josh - Welcome to the Forum .

 

[Pete999]

Cant remember the exact values on continuity, but it was a high level of resistance.

There are some kitchen appliances left to be checked, but those are on fused spurs so i suppose a fault could still come back up the netural if only single pole switch.

IR getting >0012 and i know its technically acceptable but its pretty low and makes me feel a bit uneasy.

IR > 0012??

 

[Wilko]

Good Morning Pete !

 

[Pete999]

Good Morning Pete !

Morning Wilko