by ericmark »
Mon May 02, 2022 8:04 am
A standard ceiling rose has 4 connections.
1 - Earth normally green/yellow and often a clamp rather than terminals.
2 - Neutral normally three terminals with blue or black wires, a wire off here will stop all lights working.
3 - Line feed normally centre again normally three terminals, normally red or brown wires, again a wire off here will stop all lights working.
4 - Switched line normally two terminals should be red or brown but often find a blue or black which should be sleeved with red or brown, but common for sleeves to be missing, this terminal with only affect the light from that ceiling rose.
Where a ceiling rose is replaced with down lights should really use a lighting junction box instead, but it is common to simply wrap the connections in insulation tape.
The big problem is often the twin and earth cable to the switch is not two red or two brown but red + black or Brown + blue and although the wire is black or blue it is a line wire not a neutral, common to find some one has in error connected this to neutral which causes a direct short circuit causing lights to trip.
The MCB is designed to stop you holding it in, so if switched on with a direct short the lever will go to on, but the MCB or RCBO will not switch on.
