IR value on ring

[SSE]

Carried out an EICR on an older installation at the start of the week prior to a mains board swap over. I had a low reading on one of the ring main IR tests, between live & neutral 0.02MOhms. I couldn’t see anything plugged in or switched on anywhere on the circuit & at that point I couldn’t gain access to the attic to see if there was anything that could affecting the test as the customer was away & it was locked. The live to earth was 150m Ohms, neutral to earth 185m Ohms. I swapped the mains over today & the circuit isn’t tripping the RCBO. If it was a fault in cable would that reading cause it to trip? Customer is home start of next week so can’t gain access to attic until then.

 

[NDG Elecs]

Neons often give a value around 0.02..
No USB sockets?

 

[westward10]

Just IR test to earth with the line and neutral connected together. Forget line to neutral readings on periodics unless you can be certain there is nothing connected across them. Why would the rcbo trip?

 

[buzzlightyear]

op did you do a globel beaten by Westworld .lol.

 

[davesparks]

You could measure the continuity between L and N to help identify whether a load is connected or not.
You could also measure the current flowing through the circuit to establish whether something is connected.

Neither of these is infallible, but it will help you to understand what is going on.

An IR of 0.2Mohm between L and N is unlikely if the IR to earth is 150Mohm (I assume the m in the OP was supposed to be M)

 

[MJPD29]

Sounds like possibly the neon of a spur on the ring

 

[davesparks]

The live to earth was 150m Ohms, neutral to earth 185m Ohms. I swapped the mains over today & the circuit isn’t tripping the RCBO. If it was a fault in cable would that reading cause it to trip?

It always puzzles me when an electrician asks this sort of question. We all learned ohms law at school, and use it regularly, and we all understand what causes an MCB, RCD, RCBO etc to trip so should be able to answer this.
The resistance between L and N is 0.02Mohms, which is 20,000 ohms, so you can calculate the current flow resulting from this using V=IR.
240/20,000=0.012A
So there will be 0.012A flowing between L and N.
Since that is significantly less than 32A no it won't cause the OCPD to trip.

Even if that was the IR to earth it wouldn't be enough to cause a 30mA RCD to trip.