125V L-N on cable at FCU

[GBDamo]

Was called out to a wall heater not working, took FCU off and both L and N supply cables had snapped off. This is a spur off a ring. I have not tested the ring as cannot isolate but all plugged in equipment is performing normally.

Voltage on the exposed ends L-N was 124V, L-E 238V.

My thoughts are loose connection at the point it spurs of the ring or damaged cable.

Any other theories?

I have two hours this evening to find the fault and make safe, can't turn the power off until 18:00.

Ta in advance

 

[Deleted member 105166]

What is the L-N voltage on the sockets?

 

[GBDamo]

What is the L-N voltage on the sockets?

I do t know as I'm not sure which socket circuit it is spurred off yet. All I do know is there are no other reports of equipment not working so, at the moment I'm assuming the rings are fine.

 

[Taylortwocities]

You may be picking up induced voltage if you are using a digital multimeter. You could see something like those strange voltages if the N is disconnected elsewhere. Either test L-N under load, or use a proper voltage tester.

 

[Wilko]

Hi - as L-E is 240V but L-N is not, I suspect you'll find N is disconnected somewhere.

 

[telectrix]

N either dissed or a bad connection.

 

[GBDamo]

You may be picking up induced voltage if you are using a digital multimeter. You could see something like those strange voltages if the N is disconnected elsewhere. Either test L-N under load, or use a proper voltage tester.

My proper voltage tester is in a ceiling in Blackpool, left it there this morning so using my Fluke 375FC clamp meter with probes to test for voltage.

When I can get in and isolate I can look for where the spur originates and get my MFT on the job.

 

[buzzlightyear]

My proper voltage tester is in a ceiling in Blackpool, left it there this morning

LOL.

 

[GBDamo]

LOL.

Got as far as the M61 on my way back before the Tourettes kicked in.

Have already had to beg the chippie to bring it back to the office for me, very humiliating.

 

[GBDamo]

Well what a lash up.

Turned out to be two 2.5 radials, no continuity on L,N or earth so unlikely to be a broken ring, on a 32A RCBO, traced one to the heater and no other points and couldn't find the second.

One neutral was sat in the RCBO terminal but not tight.

Found about half a dozen other C2s on the three circuits I tested so disconnected those I could and left.

Will be back another night.

 

[Octopus]

Found about half a dozen other C2s on the three circuits I tested so disconnected those I could and left.

Hum ........ you have no rights to leave such issues disconnected.

 

[GBDamo]

Hum ........ you have no rights to leave such issues disconnected.

Yes I do, i have the trust of the customer not to leave them without critical equipment while leaving the site as safe as possible, these were non critical circuits.

Obviously I wouldn't have done this with 90 year old Doris leaving her with no heating and hot water, be more inclined to stay a few more hours to resolve.

 

[The Ghost]

Last time I had those figures someone had connected neutral to earth and earth to neutral on a lighting circuit. It was a TN-C-S supply.

 

[ferg]

Ahh sorry but no. I'm afraid I won't be able disconnect your unsafe electrics until I can return because some bloke on the internet told me I have no right.