Neutrals looped at the ceiling rose

[Jupiter01]

I’m not sure I am using the loop term correctly but in my experience the wiring loop for lighting is either at the ceiling rose or the switch. This will include the live feed in, out and switched live.

I was replacing a light fitting today and noticed that it had two neutral wires and one live (switched live I assume) at the ceiling. No earth.

I assume the live in and out were at the switch. Is this normal and does it have any rationale?

 

[CBW]

Are you sure it was neutral and not just a blue wire being used as switched live but no brown sleeving to show being used as a live conductor?

 

[Jupiter01]

Yes it was Neutral as it was wired into the N terminal of the light fitting

 

[sparkwright]

It sounds like the permanent live loop (and perhaps the earth loop) is pushed up in the ceiling void.

OR

It is round conduit wiring (where the permanent live loop is at the switch, and metal conduit is the earth).

OR

The circuit is wired in sheathed single core and one cord+earth cable - where I would expect the permanent lives only to be looped at the switch.

OR

Someone has borrowed a neutral only from the light fitting.

OR

Something else.

 

[plugwash]

If you were/are wiring a lighting circuit with single wires, this would be the way to do it with the minimum number of connections, permanent live would go to the switches, neutrals would go to the lights and then a switched live conductor would go from each switch to the corresponding light.

However, while single wires in conduit, insulated and sheathed single wires and "single and earth" cables are legitimate installation techniques, most of the time we do our wiring with "twin and earth" cables.

There are a few schemes one can see with cables. The main ones are.

The "loop at light" method: Cables carrying neutral and permanent live run to the light fittings, another cable then takes permanent live down to the switch and brings switched live back up again.

The "loop at switch" method: Cables carrying permanent live and neutral run to the switch boxes, another cable then brings neutral and switched live to the light.

The "junction box" method: Cables carrying permanent live and switched live run to junction boxes. From each junction box two more cables are run, one carrying permanent live to the switch and bringing switched live back. The other taking neutral and switched live to the light fitting.

Conductors and terminals with only basic insulation should be suitably enclosed within an appropriate insulated or earthed enclosure.

Unfortunately, while traditional UK ceiling roses and batten holders are designed to accommodate loop at light wiring, many light fittings are not. This often leads to dodgy wiring practices when fittings are replaced. It is not at all unheard of for installers to put the permanent lives in a terminal block and stuff it up into the void above the fitting, then take the individual wires into the light.