Strange/Unusual Fault

newfutile said:

It’s bad practise to add RCD to comply with ADS ,this would not work on a Line-Neutral fault . This would be a departure from the regulations which does not improve safety , its better to run a bigger cable or parallel cables or even an extra R2 (cpc)

Click to expand...

Mikegh said:

When you're IR testing the connected loads at the outlet

How can you be sure you're actually getting everything

Some stuff may not be in-circuit until aftehe supply is energised


Ime SWA faults show on 500v or 1000v , could be wrong though but usually depend on the IR tester to find an issue on fixed wiring

Click to expand...

Pete999 said:

Are you testing just the installation, or the power consuming equipment? two different testing procedures ime

Click to expand...

Mikegh said:

I was responding to the first post where he said he had IR tested the SWA run and then IR tested.the equipment with L+N connected

I'm saying you may not be effectively checking all the wiring on the connected load as some may not be in-circuit when supply is disconnected

Click to expand...

Mikegh said:

I was respkndiu to the first post where he said he had IR tested the SWA.eun and then IR tested.the equipment with L+N connected

I'm saying you may not be effectively checking all the wiring on the connected load as some may not be in-circuit when supply is disconnected

Click to expand...

Lucien Nunes said:

I agree, and it woukd be helpful to confirm the gate operator leakage current when energised. But one of the OP's key points was that it is difficult to get the RCBO to hold with just the cable connected, and the loads completely unplugged. And the cable IR tests very good. I think we're going round in circles now, there's no mystery here IMO.

Click to expand...

Pete999 said:

Then if it's that strange carry out two seoerate tests , the wiring and the power consuming equipment \, to try and eliminate one from the other, no good just testing it all in one procedure, any good detective will tell you to eliminate one area at a time just saying, others may call me an idiot, but been called worse. and have a thick skin.

Click to expand...

Lucien Nunes said:

He did say clearly in post #1 that the loads were tested separately and the problem was still there with them disconnected.

Presumably the socket was included in the IR tests that showed 70 / 140 megs? In which case it doesn't seem to be particularly suspect.

Click to expand...

mattg4321 said:

So there I was the other day posting on here about me going to solve faults others couldn't find and I've got one myself.

It's been a while since I've been stumped but I am now.

Symptoms - gate supply keeps tripping (when it's raining according to customer). There's a 6mm 3 core SWA running about 3-400m (yes you read that right), to a cabinet by the gates where there is a double socket inside feeding a right mess for the gates. Protected by Hager reduced height 20A RCBO.

Unplugged both sockets, IR tested cable from consumer unit to double socket.

L-N = 140Mohm
L-E = 71Mohm
N-E = 70Mohm

IR tested the plugs for the gate controls. L&N together to earth. One was 12Mohm, the other was 299Mohm. Throughout all the below I never plugged the gates back into the double socket.

With the plugs still unplugged and nothing in the double socked I went to turn on the RCBO. Took 4 goes to get it to stay in. No bang, just as if there was N/E fault there. 1/2 trip and ramp tested RCBO and both returned no result as it tripped so early/quickly. Removed outgoing cables from RCBO and all tested well - 23mA ramp test and turned on without any trouble.

Changed RCBO to rule that out and same symptoms.

Tested IR a few more times to make sure and same results. Tested outgoing cables to socket to all other cables in consumer unit to see if anything was mixed up. All good. Physically traced cables in consumer unit to check same and again all good.

I'm guessing it's something to do with the length of the cable? I can only guess that somehow I'm losing current from the line to the earth as they are run alongside eachother for such a distance? This doesn't really make sense to me though. Someone put me out of my misery!

Click to expand...