Never seen this before............

[Crosswire]

Went to a house today where outside lights were tripping the rcd.

1.5 swa from house to ip box containing timer, which controlled a few sets of lights - wall lights, light in bin store, and drive over lights.

Each group of lights had one cable from ip box , all fairly standard stuff.

Anyway split all lights apart and touch them on one by one to live feed to find faulty lights quickly ( was the drive over lights full of water, but this is not the point) .When I touched the wall light on I got a belt off the neutral which was hanging loose and brushed my hand !

Seperated cable and found it did ONE wall light (230v ES).
When lamp was put in got 230v on neutral .
Tried three different testers all showed 230v
Meggered cables all perfect readings
Connected this light on it's own to feed and energised - didn't trip breaker or RCD and light worked fine!
Went to board tested neutral and earth bars - 0 v.

It was my understanding that the resistance of the lamp should cause the voltage to drop to 0v across the load, and the neutral should be a return path for current, not voltage!

Anyone explain this ?

*Disclaimer * Please no-one post about 'safe isolation procedure' etc.. I know what I did is not textbook, but it is QUICK. The point of this thread is the strange voltage on the neutral, and nothing else. Cheers!

 

[davelerave]

no- you'll get a belt off it

 

[IQ Electrical]

Went to a house today where outside lights were tripping the rcd.

1.5 swa from house to ip box containing timer, which controlled a few sets of lights - wall lights, light in bin store, and drive over lights.

Each group of lights had one cable from ip box , all fairly standard stuff.

Anyway split all lights apart and touch them on one by one to live feed to find faulty lights quickly ( was the drive over lights full of water, but this is not the point) .When I touched the wall light on I got a belt off the neutral which was hanging loose and brushed my hand !

Seperated cable and found it did ONE wall light (230v ES).
When lamp was put in got 230v on neutral .
Tried three different testers all showed 230v
Meggered cables all perfect readings
Connected this light on it's own to feed and energised - didn't trip breaker or RCD and light worked fine!
Went to board tested neutral and earth bars - 0 v.

It was my understanding that the resistance of the lamp should cause the voltage to drop to 0v across the load, and the neutral should be a return path for current, not voltage!

Anyone explain this ?

*Disclaimer * Please no-one post about 'safe isolation procedure' etc.. I know what I did is not textbook, but it is QUICK. The point of this thread is the strange voltage on the neutral, and nothing else. Cheers!

But the 'neutral' wasn't a 'neutral' while it was disconnected, was it?

 

[telectrix]

if the neutral is not connected back to the cu, then there is no current flow throughn the lamp. therefore there is no volt drop across the lamp. therefore the neutral is sitting at 230volts. ssssimples.

 

[sparkinlee]

if the neutral is not connected back to the cu, then there is no current flow throughn the lamp. therefore there is no volt drop across the lamp. therefore the neutral is sitting at 230volts. ssssimples.

I was about to say that...

 

[sparkinlee]

This is also the reason that fuses in the neutral conductor are a really bad idea!!

 

[Crosswire]

if the neutral is not connected back to the cu, then there is no current flow throughn the lamp. therefore there is no volt drop across the lamp. therefore the neutral is sitting at 230volts. ssssimples.

Ah of course! Now I understand................LOL

Thanks for enlightening me

 

[telectrix]

don't worry. that one caught me once.

 

[baldsparkies]

What your describing is not that far from a shared neutral scenario. Same result !! You get a belt. Always treat neutrals with the same respect you treat a live conductor. You live longer that way. :devilish:

 

[davelerave]

it is a live conductor

 

[hasel5]

Bet it hurt as well as looking for a return path

 

[mogga]

Worst belt iv had was a neutral jumped out a badly made J.B. opened lip out it jumped like a ruddy cobra

 

[Deleted member 9648]

Despite the disclaimer if you carry on 'testing' like that you are going to come a cropper one day........your funeral.

 

[Spudnik]

I have had this a few times.

And it hurts more than a 'normal' belt.

 

[baldsparkies]

it is a live conductor

I would say a neutral is a neutral.
It can be at the same potential as a live, I agree there, but its a return after the load, and its voltage is dependant on the resistence of that load.
Thats why you treat it with the same respect.
A corpse aint gonna argue either way.