Current in Live and Neutral wires in FCU

sillygoose

you could only have 234 volts on the lights Neutral if that point is not getting back to an actual neutral - as if one of the conductors in the cable is broken.

***** SAFETY NOTICE You must not connect your multimeter to the wiring on a Resistance setting while the power is on ********

So turn the power off, set the meter to resistance (Ohms) on the lowest range. Check it by touching the probes together and you should get less than 1.

Then measure between the light terminal and the neutral on the power socket, again you should get low reading probably less that 1 ohm.

Ainsley1

[edit posted before I noticed silly goose's post above]

It is a bit concerning that the probable problem has been described and you have not found it. You should maybe question if you are competent to do this job owing to lack of understanding. Not trying to insult you but you really ought to understand the basics before you start!..... but if you learn quickly and work safely......you may wish to press on!

So, it sounds that you have the problem already described where the neutral is not connected properly (in the fcu to light section) and voltage passing via the lamp ...or, if no lamp connected, a live to neutral connection that should not be or a bit of leakage from live to an open circuit neutral that may well show up as 230v by the multi meter.

You need to power of again at the mains and then test it is off where you previously had voltage shown at the spur connection to confirm this.
Then use your multimeter to test the resistance along the circuit live to live and so on then neutral to neutral and so on from spur through to the light fitting terminals. Each one should be low (probably less than 1ohm).

For good measure also test the earth wires from spur right through to light fitting which again should be low.

There are other ways to do the test but that one is simple. You may need a long wire to reach to one point from another if they are not close enough for the meter leads.

At the same time (assuming throughout here that it is not a transformer or electronic based lamp fitting) with the lamp disconnected (unplugged/unscrewed) you should also check the insulation reading between live/neutral, live/earth and neutral/earth when the spur is disconnected. This will not prove safety is adequate but will give an indication of fault conditions. These reading should all be very high and possibly the meter may indicate open circuit but certainly over 1MOhms (million ohms)

Post your results and somebody can then comment.

Risteard

Ainsley1 wrote: »

At the same time (assuming throughout here that it is not a transformer or electronic based lamp fitting) with the lamp disconnected (unplugged/unscrewed) you should also check the insulation reading between live (sic)/neutral, live (sic)/earth and neutral/earth when the spur is disconnected. This will not prove safety is adequate but will give an indication of fault conditions. These reading should all be very high and possibly the meter may indicate open circuit but certainly over 1MOhms (million ohms)

I doubt he has equipment capable of generating 500V d.c. for the purposes of insulation resistance testing.

warehouse

You want advice? Put down your tools and call an electrician first thing tomorrow.

Ainsley1

Quite right Risteard. That is why I added the caveat that it would not prove safety but it would however show up a poor resistance path where there should not be one such as would be the case of z live neutral faulty connection.

I have a lot of sympathy with warehouses post hence why I had originally questioned competence. Some things are really very simple when you have that competence and when you do not it is worth paying for, indeed often a stautory requirement that competence is fundamental to planning or doing a job.

On such a forum such as this responsible posters ought to highlight the pitfalls, value and cost of both approaches and for this job, given the questions and OPs responses I agree the 'employ an electrician's might be a wise move for the job but also to just learn a bit is no harm!

thescouselander

Op, could you show us a picture of the switch unit and the wiring?

Grenage

I agree with the above, these questions really are an indication that you should not be doing what you are doing; you could kill someone.

cool_dude_2000

Chaps, I appreciate the concern but having done electrical work in the past and taking all safety precautions I can assure you I am sufficiently competent and not stupid enough to risk my life unnecessarily. And even the most experienced of us were learners once before.

I'll try the resistance test and let you know how i get on.

Risteard

cool_dude_2000 wrote: »

I'll try the resistance test and let you know how i get on.

Once again you can't possibly conduct an insulation resistance test because you absolutely wouldn't have the equipment to do so, let alone the knowledge of how to do it.

jbainbridge

Pictures would really help up confirm you are doing it correctly.

There is a fuse in the FCU?