L-N IR results indicating fault or load left on?

[HappyHippyDad]

I have had to fault find on a very old, big house (with a bad damp problem) as the MCB feeding the kitchen sockets is tripping. There is no RCD.

It is a ring circuit. The IR results L-E are 0.003MΩ. L-N IR results indicated something left plugged in (really sorry but I can't find the note I made of the results!) I kept finding more sockets hidden away in cupboards and switches hidden above cupboards that were part of the ring and each time thought that has got to be the final load disconnected on the circuit, but the IR results still indicated a load.

I have traced the poor IR results for L-E and the tripping has stopped but I would have liked to have got a >1MΩ reading for L-N.

I suppose my question is, are there specific(ish) IR results for things left plugged in compared to a fault so that you could identify which it is?

 

[Pete999]

It's a bummer I know but you really need to isolate all loads, if what you say is true and damp is an issue, is there anyway you can try and dry out any damp areas, I realise it's not the done thing, but is the property lived in? if not and you cold ensure no access then you could drop off the front plates, leaving them connected of course, and get some air circulating, but only if you have control of the house. Just one question what voltage were yoy testing IR at?

 

[Bobster]

What was the L&N>E Results?

 

[HappyHippyDad]

It's a bummer I know but you really need to isolate all loads, if what you say is true and damp is an issue, is there anyway you can try and dry out any damp areas, I realise it's not the done thing, but is the property lived in? if not and you cold ensure no access then you could drop off the front plates, leaving them connected of course, and get some air circulating, but only if you have control of the house. Just one question what voltage were yoy testing IR at?

250V Pete.

What was the L&N>E Results?

I know its crap Rob, but I just can't find my notes with the results! I have to return so I'll get some more. What were you thinking?

 

[Bobster]

I know its crap Rob, but I just can't find my notes with the results! I have to return so I'll get some more. What were you thinking?

This will quickly distinguish if its a load still on the circuit.

 

[Pete999]

HHD sorry to be negative, get all the loads dissed and wack 500v L-N,L-E, L-N,N-E DISSED FROM THE CU

 

[HappyHippyDad]

This will quickly distinguish if its a load still on the circuit.

Could you expand a little? The L+N -E test would have been at highest 0.003MΩ as L-N was 0.003MΩ, how would this indicate if there was a load still on? With fault cleared the L-E was somewhere around 2MΩ and N-E was something similar.

 

[HappyHippyDad]

HHD sorry to be negative, get all the loads dissed and wack 500v L-N,L-E, L-N,N-E DISSED FROM THE CU

This is a real DIY house Pete (in terms of electrics). I have a feeling there are going to be all sorts hidden under the floorboards and behind kitchen units. It may be big and old but its immaculate and lived in. I've gone over everything again and again and cannot find this load, hence thinking it may be a separate fault (although tripping has now stopped since L-E results improved).

 

[Octopus]

Did you split the ring at all too narrow down the low IR?

 

[HappyHippyDad]

Did you split the ring at all too narrow down the low IR?

I split the ring a number of times to find the low L-E results as I was focused more on these than the L-N. Did you mean the L-E or L-N?

 

[Octopus]

I split the ring a number of times to find the low L-E results as I was focused more on these than the L-N. Did you mean the L-E or L-N?

Both. ...

 

[Deleted member 9648]

TBH I wouldn't worry overly if your readings to earth are sound,and you are still getting a L-N reading. It will almost certainly be an untraced load. Bear in mind that T/E cables have a bare copper earthed wire between the live cores, so a L-N fault on wiring without anything showing up to earth is highly unlikely....(assuming T/E of course). If the load was not traced in a reasonable time I would probably issue a MW form explaining a likely untraced load being the cause of the low L-N IR result

 

[tomspark93]

Sometimes worth looking outside as well for anything obvious, outside supplies/sockets/lights. Common things that have thrown me in the past are heating, TV amps, Electric fires, RCD SFUs, sockets with surge protector extensions plugged in behind kitchen units/behind plinths and behind fitted wardrobes.

 

[PEG]

Hi bud,how and when has that MCB been unlatching? If it is of the size we imagine,there should be an amount of damage occurring somewhere,and this may explain a persistent,repeated IR reading.

It is split and persevere,i'm afraid:willy_nilly:

 

[TJ Anderson]

I have had to fault find on a very old, big house (with a bad damp problem) as the MCB feeding the kitchen sockets is tripping. There is no RCD.

It is a ring circuit. The IR results L-E are 0.003MΩ. L-N IR results indicated something left plugged in (really sorry but I can't find the note I made of the results!) I kept finding more sockets hidden away in cupboards and switches hidden above cupboards that were part of the ring and each time thought that has got to be the final load disconnected on the circuit, but the IR results still indicated a load.

I have traced the poor IR results for L-E and the tripping has stopped but I would have liked to have got a >1MΩ reading for L-N.

I suppose my question is, are there specific(ish) IR results for things left plugged in compared to a fault so that you could identify which it is?

Agree totally with Wirepuller. You have found and rectified the earth fault, which would have been at least a fairly heavy fault due to not having RCD on it and purely an MCB protecting circuit. What did you find and rectify out of interest? Would also recommend you price to add 30ma RCD either just to that circuit or CU upgrade and explain benefits. Did you also take a reading L-N with low ohm continuity range?

 

[Lucien Nunes]

I believe he's fixed that problem - HHD what actually was the fault to earth?

Tomorrow when I'm less knackered (been working nearly 40 hours) I'll do a spotters' guide to loads as seen from the other end of a circuit.

 

[HappyHippyDad]

Agree totally with Wirepuller. You have found and rectified the earth fault, which would have been at least a fairly heavy fault due to not having RCD on it and purely an MCB protecting circuit. What did you find and rectify out of interest? Would also recommend you price to add 30ma RCD either just to that circuit or CU upgrade and explain benefits. Did you also take a reading L-N with low ohm continuity range?

I believe he's fixed that problem - HHD what actually was the fault to earth?

Tomorrow when I'm less knackered (been working nearly 40 hours) I'll do a spotters' guide to loads as seen from the other end of a circuit.

I perhaps split the ring 5 times in different places, each time I thought this may well be the faulty socket as they were full of damp and even little puddles in some. However, the fault was on a spur where the earth had no sleeving and there was a nick in the line conductor. There were some nasty scorch marks. Fault cleared when this was rectified.

 

[HappyHippyDad]

I believe he's fixed that problem - HHD what actually was the fault to earth?

Tomorrow when I'm less knackered (been working nearly 40 hours) I'll do a spotters' guide to loads as seen from the other end of a circuit.

That sounds very interesting Lucien, thank you:smile5: