Interesting Fault.

[securespark]

Woo Woo!!

Bernard in a nightie!!

Gizza flash!

 

[bernardgreen]

Woo Woo!!

Bernard in a nightie!!

Gizza flash!

No way. the lights here don't work so I can't find anything to wear and the batteries for the camera are missing.

 

[securespark]

the lights here don't work

You need a decent sparkie, mate.

 

[bernardgreen]

the lights here don't work

You need a decent sparkie, mate.

But decent sparkies never wear nighties........

 

[studentspark]

sorry,not quite getting this.
The switch drop is switching the live and neutral?

any further explanation would be appreciated

Thanks

 

[fireman22]

studentspark, just think of it as the last light, two cables, with a junction in the switch drop, it was probably a red and black cable so the switch drop junction looks like a live & neutral, when the switch is off the red is 230 volts and the black in neutral through the lamp. draw it out and you will get it

 

[bernardgreen]

when the switch is off the red is 230 volts and the black in neutral through the lamp. draw it out and you will get it

The black at the switch is not neutral, it is always switched live.

When the switch is off the black wire may be at neutral potential if there is a filament lamp in place. With low energy lamps in place the switched live can be any voltage due to capacitive coupling to the live in the switch cable.

If it was neutral you could power a one kilowatt heater from it when the switch was off. If you did try that you would find the heater would be cold and the lamp brightly lit when the switch was OFF

 

[ban-all-sheds]

But decent sparkies never wear nighties........

Not even Sparkybird?

 

[fireman22]

bernardgreen are you being serious? i know its the switched live i was trying to explain it in simple terms so student spark could understand whats going on and why (probably) the outside light would work when the switch was off.

 

[sparkybird]

NIGHTIES ARE FOR WIMPS!

 

[ban-all-sheds]

 

[bernardgreen]

bernardgreen are you being serious?

Yes, a switched live is not a neutral..

 

[ban-all-sheds]

And what's more it should NEVER be referred to as one, because doing so reinforces the mistaken belief that blacks are always neutral, that a switch does things magical and doesn't actually connect the two cables together inside, that all the blacks can be connected together at the ceiling rose, and so on.

i know its the switched live i was trying to explain it in simple terms so student spark could understand whats going on.

You were doing the exact opposite of helping him to understand what's going on.

 

[fireman22]

i didnt say it was a neutral i said because they probably used red & black as a switch cable it looked like a live & neutral in the junction.

 

[securespark]

Yes, in fm22's defence, he said it looks like a neutral.

He also said the black would be a neutral through the lamp, which it is, when the light is off.

Ban

I have no pix, but it's simple to visualise.

There are two light fittings wired 3 plate in a bedroom, both switch cables terminate in a JB in the loft. Another T&E goes down to the switch. All reds, blacks and cpc's are together in the JB.

Someone comes along and fits a coach lantern outside via a photocell. They tap a feed off the switchwire JB, mistaking the switched live for a neutral.