fault on N&L to CPC

[jimmy]

It's been a few years since college and I'm stuck on understanding this,

I'm getting an intermittent fault on kitchen sockets. Causing some tripping.

Broken it down and when I IR test the circuit. L to E is 200+
N to E is 200+
But when I test N&L to E thruster fluctuates between 120Mohnm to 160Mohm

I don't understand why it's over 200 M when I test separately.

Can anyone explain to my stupid brain please. TA

 

[thebigcheese]

Assuming both N-E and L-E have an IR of 220Mohm then the combined IR would be much lower:
1/(1/220+1/220)= 110Mohm

This would explain your situation but whether it's the actual cause or not I don't know!

 

[telectrix]

a reading of 120 Meg is good enough to be ignored. your fault is more likely to be an appliance.

 

[jimmy]

fault on N&L to CPC

Definitely not an appliance. Thanks big cheese that explains the reading. It's now dropping down to 30Mohm now and again.

So how can I trace intermittent faults without rewiring everything?

 

[telectrix]

if the circuit is a ring. guesstimate the mid point and split it. then you may well find a low reading on 1 leg. then split that leg again.... and so on till you narrow it down. even so, 30Meg. will not trip a RCD.

 

[jimmy]

fault on N&L to CPC

Spent hours doing that. I get 200+ on leg L&N to E then 10mins later back to below 100Mohm.

I'm worried about the fault to other causing problems to the ladies appliances.

 

[Lucien Nunes]

Have you taken the sockets off the wall? Is anything damp / newly plastered / decorated? How old is the install? 30M should be findable and I personally would look for it because it could direct you to the site of cable damage etc; a short length of T+E and a few fittings should be able to get over 30M. But 100M... a few years ago your tester wouldn't have been able to read that high. I wouldn't exactly call it a fault and it wouldn't cause any other problems.

 

[jimmy]

fault on N&L to CPC

Well I've put all sockets back on and it's reading 200M+ L&N combined. Don't know why. Maybe fiddling with sockets?? Who cares I'm walking away now

 

[DPG]

Re: fault on N&L to CPC

Well I've put all sockets back on and it's reading 200M+ L&N combined. Don't know why. Maybe fiddling with sockets?? Who cares I'm walking away now

That's that one sorted then! Ermmm....... Daz

 

[telectrix]

could have been a cable caught up by a screw or squashed against the back box. by pulling the faceplate off and refitting, you could have cleared the fault.

 

[Engineer54]

Re: fault on N&L to CPC

Well I've put all sockets back on and it's reading 200M+ L&N combined. Don't know why. Maybe fiddling with sockets?? Who cares I'm walking away now

Maybe a theory refresher course is called for here!! lol!!

 

[bigspark17]

fault on N&L to CPC

Did you IR L-N.??

 

[jimmy]

Did you IR L-N.??

Yes that was fine.

May of been the socket. Think I would of picked up on that though. I've pulled a couple of cables through and remade so may be snagged on something.

All sorted though.

 

[sparky351355]

Damp maybe a prime suspect on this one, or the old bottle sterilizer right next to socket or kettle etc . U could remove all sockets and connector block the ring and test cable only. Just s thought!