Voltage Pen and weirdness

[Cypermethrin]

I bought a Voltage Tester Pen thinking it would be useful

https://www.amazon.co.uk/Schneider-Electric-Rapitest-IMT23009-Voltage/dp/B00LY1CGYC

However I am now very confused by it.

I turned off the fuse for the lights in the lounge; but the Pen Tester still lights up on the feed to each spot light - but checking with a volt meter all connections shows no volts.

What am I missing here ?

 

[flameport]

What am I missing here ?

a. capacitive coupling between cables
b. tester pens, tester screwdrivers and the like are totally useless for confirming there is no voltage.

 

[Cypermethrin]

a. capacitive coupling between cables
b. tester pens, tester screwdrivers and the like are totally useless for confirming there is no voltage.

Thanks for your rapid reply and counsel - looks like its going back to the shop !

I have another numptie question.

Same scenario - fuse off; no lights in lounge working; zero volts on digital voltmeter

I use wire cutters to simultaneously cut through all three feed wires to a downlighter (i.e., live, neutal and earth cut simultaneously). This caused the main fuse for all circuits in the house to trigger.

Why would this be ?

 

[JohnW2]

I use wire cutters to simultaneously cut through all three feed wires to a downlighter (i.e., live, neutal and earth cut simultaneously). This caused the main fuse for all circuits in the house to trigger. Why would this be?

Would this 'main fuse' perhaps have been an RCD (a 'breaker' with a test button)? If so, it will have been because your wire cutters connected the neural and earth conductors in the cable (removing the fuse only disconnected the live, not the neutral).

Kind Regards, John

 

[Cypermethrin]

Would this 'main fuse' perhaps have been an RCD (a 'breaker' with a test button)? If so, it will have been because your wire cutters connected the neural and earth conductors in the cable (removing the fuse only disconnected the live, not the neutral).

Kind Regards, John

It was indeed an RCD breaker - thanks for your answer and kind explanation. makes perfect sense. Thanks

 

[JohnW2]

It was indeed an RCD breaker - thanks for your answer and kind explanation. makes perfect sense. Thanks

You're welcome.

A slightly longer explanation is that the RCD will be serving several circuits, not just the one for which you removed the fuse, and even after you had removed that fuse, the neutrals of all those circuits would still be connected together. Assuming that something(s) on those other circuits was/were drawing current at that time, when your wire cutters connected neutral and earth, some of that current would have 'leaked' to earth, rather than all going through the neutral side of the RCD.

An RCD detects any difference between the currents in live and neutral conductors. They are normally the same, but if some current 'leaks' (from either live or neutral) to earth, then the the L and N currents through the RCD will become a bit different, thereby causing the RCD to trip.

Hope that helps.

Kind Regards, John

 

[ban-all-sheds]

And even when you kno fool well that's what an RCD does, don't want to turn everything off, and promise yourself that you'll be very very careful to avoid a N-E short, it seems that at some point there's always a muttered "%$£@#~^!" and a louder "Sorry!" to everyone else in the house.

 

[JohnW2]

And even when you kno fool well that's what an RCD does, don't want to turn everything off, and promise yourself that you'll be very very careful to avoid a N-E short, it seems that at some point there's always a muttered "%$£@#~^!" and a louder "Sorry!" to everyone else in the house.

I'm glad it's not only me

As I've often said in relation to discussions about 'nuisance' RCD trips, I've lived with about a dozen RCDs for 20+ years andhave a experienced very few trips of any of them (other than in the name of testing). A very small number have been 'appropriate' trips (usually water in outside lights etc.), but nearly all the others have come about in the manner you describe above!

Kind Regards, John

 

[SUNRAY]

What a nice thread!

 

[securespark]

You looking at me?

Ey?

 

[SUNRAY]

A nicely written OP.
Sensible advice
and a little bit of humour.