low voltage reading on wall lights

[sarahproperty]

my electrician installed the cables and switches for the wall lights. i am now just second fixing the lights to the cables.

the problem is that two wall lights (with two way switching) won't work.

when the switch is turned on, the voltmeter reading says 198. i normally get a reading of 250 on other lights and sockets etc.

a friend suggested a "break in the neutral".

the problem is that the walls are plastered so i cant tell which cable runs to where to see where this problem is.

all the other lights in the house are fine, including other two way lights.

i know which cable brings the power from the fuse board to power the lights in this room. all the other lights running off this cable are fine.

i've tried removing the cover off the fuse board and there is no obvious way of telling if the electrician has run the neutral from those lights to straight to the board.

alternatively, is the problem definitely a break in neutral or could it be a loss of voltage due to too much resistance? eg the power comes in to the com on the first switch, which is the switch for these lights, and then the com on 4 other switches are linked off this.

any suggestions? i have tried removing the light fittings and still get a reading of 198 on the cables poking out of the walls where the light should be fitted.

 

[bernardgreen]

Sarah

The 198 volts would light the lights if it was a "true" voltage. The fact that the lights do not light shows the voltage is there as a result of inter-conductor capacity.

Voltage drop along wires and across switches would never get as much as 32 volts ( 230 -198 ) on a domestic installation.

There is quite possibly a wiring error in the two way switching.

 

[sarahproperty]

so, do you think i should try switching the L1 and L2 cables around? in case they are the wrong way round? they seem to be the same colour on both switches?

or do you think that the cable from the com in the second swtich is not going to the right place?

any practical solutions are greatly appreciated.

 

[Sarahspark]

Why don't you just call your electrician back?

Sarah

 

[sarahproperty]

dont know the electrician's number any more, the wiring was done ages ago. it took me zonks to choose the light fittings!

 

[jj4091]

How many cables with how many cores+ colours do you have at each light & each switch?

 

[sarahproperty]

he hasnt used four core cable, just used three core and occasionally used the non sheathed part of the cable (usually used for earth) and covered this with brown sleaving.

so it is very hard to work out where the cables go as they all look the same, ie mostly brown and a few blue.

 

[sarahproperty]

bernard, what is inter-conductor capacity?

 

[bernardgreen]

bernard, what is inter-conductor capacity?

It is the effect where a change in voltage on a wire will cause a change in voltage on all nearby objects even though they are not connected.

If one wire in a cable has live AC voltage on it then a voltage equal and opposite will be created on the other wires in the cable that are not connected to anything. The induced voltage is "weak" in that it can only support a very small current and the few millionths of an amp that the multimeter takes will reduce the induced voltage. In your case from 230 to 190

 

[scousespark]

he hasnt used four core cable, just used three core and occasionally used the non sheathed part of the cable (usually used for earth) and covered this with brown sleaving.

so it is very hard to work out where the cables go as they all look the same, ie mostly brown and a few blue.

If you really have earth core sleeved with brown this could potentially be a dangerous install. I would suggest you get another spark in to test the circuits. The original spark should have left a certificate showing the extent of his work and test results. If you have this it should have his contact details.

 

[bernardgreen]

he hasnt used four core cable, just used three core and occasionally used the non sheathed part of the cable (usually used for earth) and covered this with brown sleaving.
quote]

If you really have earth core sleeved with brown this could potentially be a dangerous install. I would suggest you get another spark in to test the circuits. The original spark should have left a certificate showing the extent of his work and test results. If you have this it should have his contact details.

If he did that would he have the cheek to issue a certificate ?

 

[jj4091]

he hasnt used four core cable, just used three core and occasionally used the non sheathed part of the cable (usually used for earth) and covered this with brown sleaving.

so it is very hard to work out where the cables go as they all look the same, ie mostly brown and a few blue.

Sorry but I do not think it is safe to try to help any further, your electrician was a cowboy I am afraid to say & as newspark_paul says, you need to get someone properly qualified in now to sort it