Current in Live and Neutral wires in FCU

cool_dude_2000

I am attempting to create a Fused spur from a power socket for some wall lights.

I have managed to fit and wire the Fused Connection Unit and spur it off the power socket. However, the lights themselves don't work and when I test with a voltage tester, both the live (brown) and neutral (blue) wires in the FCU are showing as having a current!

I've checked the connections which seem to be fine, so I'm struggling to understand what I've done wrong. The wires from the power socket are all connected into the connections marketed IN and the wires to the lights are in the ones marked LOAD.

What am I doing wrong?

YorkshireBoy

First of all you're measuring voltage, not current, with a "voltage tester"! You'll draw a current when you create a circuit, ie when the lights work!

So to clarify, you have 230V between L (SUPPLY) and N (SUPPLY)?

And you have 230V between L (LOAD) and N (LOAD)?

Do you have 230V at the light fitting(s)?

sillygoose

I am guessing by voltage tester you mean one of those Neon lamp screwdriver testers?

If its indicating (Voltage!) on both your Live and Neutral lines its likely your Neutral isn't connected correctly back at the socket you spurred off.

If the neutral is then 'floating' it will become live via the live voltage going through the lamp onto the Neutral.

Turn the power off fully and check your Neutral connections, perhaps it broke off or pulled out on the power socket when you refitted it, or you screwed the terminal onto some insulation instead of bare copper.

cool_dude_2000

That's great advice. Many thanks.

cool_dude_2000

So if taken a look at the connections and they all seem fine. However I've noticed that if I disconnect the wall light then there are no longer any volts running in the neutral (load).

thescouselander

Could you clarify how you're measuring the voltage on the neutral connection?

What device are you using and how are you connecting it?

paddyrg

Voltage is always measured between two points - if you're using a glowy screwdriver, you're the second point.

cool_dude_2000

I'm using a tester screwdriver which has a neon light when making contact with the connection terminals at the back of the FCU.

Le_Kirk

You really need to use a multi-meter to check for voltage (not current) so back to basics I think. I assume you are turning off the power before connecting new cables into the existing socket, so first of all turn off the power then remove the cables you inserted into the existing socket, leaving the original cables connected. Check between L & N for 230 Volts - this is good. Check between L & Earth for 230 volts - this is also good. Check between N and Earth for any voltage - this is not good and if you have voltage here you have a neutral wiring fault somewhere.

Assuming all good between N & Earth, disconnect the load from your new Fused Connection Unit (FCU), connect your new cables into the existing socket, make sure you connect L into Live IN and Neutral into Neutral IN on your FCU, turn on the power, carry out the same checks as above but in the new FCU. If all good, switch on the FCU and check for 230 volts on Load terminals. If all good, switch off power, connect light into FCU. Turn on power, switch on lights, sit back and enjoy a cup of tea.

sillygoose

cool_dude_2000 wrote: »

So if taken a look at the connections and they all seem fine. However I've noticed that if I disconnect the wall light then there are no longer any volts running in the neutral (load).

It still sounds like your Neutral is not connected.. with the wall light connected, does the tester light up on the OUT side of the FCU and the IN side? - if so there has to be something wrong with the connection between the FCU and the wall socket...

either the wire is broken somewhere along its length internally, or the bare end of the wire into the socket terminal is not making a connection or the same at the FCU IN terminal.

(The only other possibility would be a twofold combination problem, if you had the Live/Neutral the wrong way round at some point and the FCU were missing the fuse or had a dud one in it, then the Neutral would be live and the lamp not work.)

cool_dude_2000

Ok, so I've bought a multimeter voltage tester and bypassed the FCU now by connecting the wires directly.

On the power socket it tests as 234 volts between live and neutral. It also tests 234 volts between live and earth. It also tests 0 volts between neutral and earth. So far so good.

However on the connection blocks to the light it tests 234 volts between live and earth and 234 between neutral and earth and 0 volts between live and neutral!

I have checked the connections countless times. The blue wires from the light fitting are connected to the black wires on the socket and the brown wires connected to the red. There are no bare or exposed wires aside from the terminals.

I really can't understand where I'm going wrong?