lighting

[The apprentice]

Hi there i went to a job guys kitchen light was not working no voltage at switch what so ever the circuit breaker was on the unprotected side of the distribution board i accidentally touched the com wire to the earth and a big spark happened and tripped the breaker never had that before in my life any ideas ?

 

[telectrix]

must have been live. what made you think it was dead? was it a volt stick?

 

[The apprentice]

must have been live. what made you think it was dead? was it a volt stick?

no honest was dead tried through my fluke t110 and my multi meter it baffled me

 

[telectrix]

you mustnot have made a good connection with your probes. bang means live.

 

[The apprentice]

you mustnot have made a good connection with your probes. bang means live.

there was 100% not any voltage at that common side of the switch i jiggled the wires about inside the conduit to see if i was getting anything and still not anything just incase there was a slack connection but it banged when touched earth but honest not any voltage present it’s confused me for days

 

[pc1966]

no honest was dead tried through my fluke t110 and my multi meter it baffled me

Rule #1 of not dying from electricity is to make damn sure it is dead before you work!

Multimeters are great, but have many ways of not telling you what you need to know (i.e. live or not) which is why they always suggest a dedicated voltage test and proving unit.

I have no idea of how big the spark was, but you can get a small one from discharging energy stored in capacitance. Seems a bit unlikely here though.

Also do they have PV or other local generation? It ought to go dead on the loss of mains but you never know...

 

[The apprentice]

Rule #1 of not dying from electricity is to make damn sure it is dead before you work!

Multimeters are great, but have many ways of not telling you what you need to know (i.e. live or not) which is why they always suggest a dedicated voltage test and proving unit.

I have no idea of how big the spark was, but you can get a small one from discharging energy stored in capacitance. Seems a bit unlikely here though.

Also do they have PV or other local generation? It ought to go dead on the loss of mains but you never know...

yeah it was dead first thing i done when opened the switch up was test for any voltage which there wasent i don’t a voltage test between the earth wire and the metal conduit i got 168 volts then done it again nothing done it again voltage present then was none voltage it was fluctuating just confused with it all and on top of that finding the joint box within the conduits is go be a nightmare but surley has to be in an accessible place it’s a downstairs 4 in a block house

 

[ChrisElectrical88]

you mustnot have made a good connection with your probes. bang means live.

Wise words. True statement.

 

[davesparks]

yeah it was dead first thing i done when opened the switch up was test for any voltage which there wasent i don’t a voltage test between the earth wire and the metal conduit i got 168 volts then done it again nothing done it again voltage present then was none voltage it was fluctuating just confused with it all and on top of that finding the joint box within the conduits is go be a nightmare but surley has to be in an accessible place it’s a downstairs 4 in a block house

If you've got a voltage of 168V between a CPC and a steel conduit then something is very wrong.

It also suggests that maybe the live conductor was in fact dead and connected to neutral via the loads of the circuit and it was the conduit which was live and caused the bang.

 

[The apprentice]

If you've got a voltage of 168V between a CPC and a steel conduit then something is very wrong.

It also suggests that maybe the live conductor was in fact dead and connected to neutral via the loads of the circuit and it was the conduit which was live and caused the bang.

the circuit breaker was on unprotected side of rcd some cow boy was in before me i really do appreciate all the comments just not opening a can of worms and would rather find the joint box and just re wire the kitchen light

 

[davesparks]

the circuit breaker was on unprotected side of rcd some cow boy was in before me i really do appreciate all the comments just not opening a can of worms and would rather find the joint box and just re wire the kitchen light

Why does anything need to be rewired?

 

[telectrix]

find the fault, fix it, get paid. sorted.

 

[ipf]

Sounds like you need some help from someone with a bit more experience. If nothing has been isolated, I wouldn't recommend 'jiggling the wires about inside the conduit' to see if you're getting something...it bites, as you nearly found out.
The fault needs finding before deciding to rewire something.

 

[cloverman]

Take the advice of those who have given you their wisdom of experience and buy yourself a dedicated voltage tester before you become a statistic on the death by electric shock register

 

[Lucien Nunes]

some cow boy was in before me

To be honest, what you were doing also sounds a bit Yeehaa to me.

The problem was that the light had stopped working, so there was a fair chance of a loose connection or bad contact somewhere. You left the circuit live and started tinkering around with it, believing that the permanent live feed was dead, even though that might well have been caused by the bad connection and ever so close to making contact again. You were trusting your safety to a tiny layer of corrosion or a wire floating about in a terminal one thousandth of an inch away from being live. I think if you refer back to your procedure for safe isolation, that doesn't count!

A broken circuit is much, much safer to find with dead tests, and sometimes easier too as you don't need to keep isolating and re-energising when you want to touch anything. Continuity to the lamp? Nope. Continuity to the switch? Nope. OK, problem is upstream of the switch. Just test methodically along the circuit until you find where the continuity ends. That way, when the fault does something unexpected, it will be the tester doing the bleeping, not you.