Tripping RCD on new Ring Main

[Octopus]

Shame the OP didn't update the thread when he dropped in last night .............

 

[elsparko]

Shame the OP didn't update the thread when he dropped in last night .............

maybe he has shorted out the live/neutral whilst live, using his fingers as a probe tester?

 

[Pete999]

maybe he has shorted out the live/neutral whilst live, using his fingers as a probe tester?

Naaaaaaa

 

[elsparko]

saying that, not all apprenticeships are equal, i was working as a sparks mate earlier this year, guy on double my wages was coming to me every 20 mins to see what to do, didnt mind helping him out as he was a road lighting sparky, only as good as what youve been taught,i should refrain from coming onto forums over weekend lol, im too mean.

 

[Electron]

Anything plugged in or connected via a fused spur?

No. Both fused spurs (Saniflow and toilet floor heating) switched off.

 

[elsparko]

disconnect the cables at the DB and shove them into the wallspace, theres nothing else that can be done sorry.

 

[Des 56]

No. Both fused spurs (Saniflow and toilet floor heating) switched off.

Are they double pole?

 

[buzzlightyear]

I have installed a new ring main in a kitchen extension and tested for continuity and insulation resistance before connecting to Consumer Unit. As soon as main switch turned on, even with all the MCB's switched off, the RCD tripped. I removed all the connections to the consumer unit from the new ring and the rest of the circuits were fine

No. Both fused spurs (Saniflow and toilet floor heating) switched off.

am I missing some thing or you!

 

[Electron]

What do you plan to do next?

Tell us and we'll give you some pointers......

I have retested the circuit. The results for continuity are r1 0.70 Ohms, rn0.7 Ohms and r2 1.13Ohms. So far so good!
r1 + r2 sockets 0.52-0.56 Ohms. I was expecting 0.46 Ohms, so a bit high.
r1+rn are all over the place. from 0.44 up to 0.86. No pattern. Should be 0.35.
The insulation resistance are Line to Neutral ˃500 M Ohms Line to CPC ˃500 M Ohms. Sadly, the Neutral to CPC was 0.
There are only ten sockets on the ring and two fused isolators.
Can anyone suggest what is causing the problem?

 

[Octopus]

Cable damage...

Time to split the ring to narrow down where the fault is

 

[Electron]

Are they double pole?

Yes both are DP Switched fused.

 

[KEV 1 N]

Cable damage...

Time to split the ring to narrow down where the fault is

Could be a nipped neutral on a metal back box at a socket or spur.

 

[Electron]

Was the cpc connected to the earthing bar in the CU when you did the IR testing?

No. I removed the cable for the ring from the consumer unit so I could leave the customer with power on the other curcuits.

 

[buzzlightyear]

how long have you been on that job ?

 

[elsparko]

I have retested the circuit. The results for continuity are r1 0.70 Ohms, rn0.7 Ohms and r2 1.13Ohms. So far so good!
r1 + r2 sockets 0.52-0.56 Ohms. I was expecting 0.46 Ohms, so a bit high.
r1+rn are all over the place. from 0.44 up to 0.86. No pattern. Should be 0.35.
The insulation resistance are Line to Neutral ˃500 M Ohms Line to CPC ˃500 M Ohms. Sadly, the Neutral to CPC was 0.
There are only ten sockets on the ring and two fused isolators.
Can anyone suggest what is causing the problem?

half the circuit and test both , repeat until fault traced.