Strange Home Electrics

[Generalchaos]

Had some weird tripping today with the Safe T Cut (set to 25ua)

The kitchen sockets were causing the Safe T Cut to trip but not the individual breakers.

Got some weird measurements when checking the resistance in the sockets, Live to Neutral was about 200 Ohms for about 30 minutes, then went back to 3 or 4 mega Ohms.

Then checked the voltages, Live to Neutral was about 220V, Live to Earth was about 235V and neutral to Earth was about 12V (AC).

I can understand that the neutral has a load and a bit of current flowing, but should the Vdrop be that high? Could it be dirt (we get a lot of termites and wasps that fill up any unused socket outlets with mud)

Checked earth to earth between all of the sockets and they are about 1 or 2 Ohms, so they seem interconnected and nothing floating around.

What would cause the high (12V) difference between Neutral and Earth?

Any ideas?

Cheers.

Sorry, I should have added that when I test the sockets on the upstairs (separate circuit) The ground to Neutral is only 5V RMS, but 36V Peak to Peak!

Edited July 25, 2016 by Generalchaos

[Crossy]

A TT system (with no local N-E link) can get pretty high N-E voltages, 12V is the upper end but not really unusual for Thailand where long and overloaded feeds are not unusual.

Your, L-N resistance measurements are interesting, but shouldn't trip the Safe-T-Cut, are you sure everything was unplugged from the circuit?

I think your, "creatures" diagnosis is likely and may account for the L-N readings too.

Remove and clean all your outlets and drop a moth-ball in the box before re-fitting.

EDIT After your edit. Please verify that ALL your neutrals are low resistance to your neutral bar. Same with your grounds.

I still think you have creatures issues as well.

[lopburi3]

You may also have had a lizard causing the low live/neutral resistance reading and he survived thanks to the Safe-t-cut and removed himself when he could. But do clean all outlets - ants and termites can really be bad news (although I always had issues with switches rather than outlets).

[Generalchaos]

A TT system (with no local N-E link) can get pretty high N-E voltages, 12V is the upper end but not really unusual for Thailand where long and overloaded feeds are not unusual.

Your, L-N resistance measurements are interesting, but shouldn't trip the Safe-T-Cut, are you sure everything was unplugged from the circuit?

I think your, "creatures" diagnosis is likely and may account for the L-N readings too.

Remove and clean all your outlets and drop a moth-ball in the box before re-fitting.

EDIT After your edit. Please verify that ALL your neutrals are low resistance to your neutral bar. Same with your grounds.

I still think you have creatures issues as well.

Cheers Crossy, yes everything was disconnected from the circuit when I made the measurements. What was interesting measuring again tonight after cleaning was that Earth / Neutral had dropped to about 3 V RMS, but what looked to be transient voltages from outside were causing some strange spikes, up to 36V at times.

I am pretty sure it is not internal as everything was isolated, nothing plugged in and only the one breaker for that circuit was opened.

We get some weird voltages here when people outside start messing with heavy welding kit etc. - Mains voltage can drop to anything, had times with 110V from the outside transformer.

I was just worried about the tripping on the Safe T Cut, but it hasn't happened again after cleaning.

The one thing of benefit however seems to be that the original Spark didn't bodge the Earth connection by tying it to the Neutral, it is definitely a dedicated circuit.

Thanks for your reply, appreciated.

[Generalchaos]

You may also have had a lizard causing the low live/neutral resistance reading and he survived thanks to the Safe-t-cut and removed himself when he could. But do clean all outlets - ants and termites can really be bad news (although I always had issues with switches rather than outlets).

Cheers,

every single unoccupied socket outlet we have is filled with dried mud from those damn wasps, termites and other creatures that like to live in holes. They even wall up my headphone jack outlets. Never found an easy way to prevent it.

I have been washing out the connectors with contact cleaner but it is not cheap here and I ran out, cleaned the sockets tonight with WD40 and that seems to work OK.

[dcnx]

You may also have had a lizard causing the low live/neutral resistance reading and he survived thanks to the Safe-t-cut and removed himself when he could. But do clean all outlets - ants and termites can really be bad news (although I always had issues with switches rather than outlets).

Cheers,

every single unoccupied socket outlet we have is filled with dried mud from those damn wasps, termites and other creatures that like to live in holes. They even wall up my headphone jack outlets. Never found an easy way to prevent it.

I have been washing out the connectors with contact cleaner but it is not cheap here and I ran out, cleaned the sockets tonight with WD40 and that seems to work OK.

Where do you live? Sounds frustrating.

Worst I've had happen is ants made a home in a remote control.

[Crossy]

Do try mothballs I'm the back boxes, just one in each, they discourage most things and are cheap.

The mud wasp's activities have caused at least one major plane crash by making their homes on unprotected pitot tubes

[thesetat2013]

Why dont you just try changing that breaker?

The breaker seperate from my breaker box kept tripping and it turned out to be something to do with the magnetics inside. i replaced it and no problem now.

[lopburi3]

Why dont you just try changing that breaker?

The breaker seperate from my breaker box kept tripping and it turned out to be something to do with the magnetics inside. i replaced it and no problem now.

The Safe-t-cut breaker tripped, as designed to do, because of a slight load imbalance between load and neutral lines (alternate path to ground). It was not an overload trip on a normal breaker.

[English Engineer]

The neutral to earth voltage can vary. The voltage is determine by the load balance between the 3 phases. I think you mean the cut out is set to 25mA. When the house electrics is handed over the continutity should be checked theoughout the house live, neutral and earth. The earth at the circuit breaker box connection should be connected to an earth stud.

[ozyjon]

You think you have problems,,,,,

[Generalchaos]

You think you have problems,,,,,

wires.jpg

The funny thing is, when you look in my breaker box and Safe T Cut connections they are beautiful, almost a work of art, every wire is bent perfectly into shape and terminated like something from NASA, then you get in the loft and behind the other panels that the Thai electricians installed and all you find is open junction boxes and about 20KG of insulating tape! They are a bunch of bodgers!

[Generalchaos]

The neutral to earth voltage can vary. The voltage is determine by the load balance between the 3 phases. I think you mean the cut out is set to 25mA. When the house electrics is handed over the continutity should be checked theoughout the house live, neutral and earth. The earth at the circuit breaker box connection should be connected to an earth stud.

You are correct, it is 25mA, our supply is not over 3 phase, I believe we have two phase HV that goes into a transformer and is distributed from there. There is no earthing from PEA just a two wire HV to the transformer box then the house feeds are taken from that.