Adam Haddad
Hi Mark, it’s perfectly fine to take another feed from the nearest rose or junction box, however there are some tests you should do before feeding another light from a circuit. 1. Perform an insulation resistance test on the lighting circuit your wish to add to. This will show you whether the current cables are in a good enough condition to withstand the extra load. Above 2M ohms is the legal limit but if it comes close to this, I wouldn’t make any alterations and rewire the whole circuit. 2. Perform an earth fault loop impedance test on the last point of the circuit, this will ensure you have earth continuity throughout, the reading will show you whether the impedance is within the limit to allow the MCB to trip within the tolerated time. If it is too high you cannot add any more lights to this circuit and should think about adding an RCD or and RCBO to the circuit for fault and additional protection. In order for you to alter any circuit you MUST have RCD protection for that circuit. If you don’t have a RCD for that circuit you could install an RCBO for that one particular circuit, that would act as an RCD and an MCB at the same time. If all of the above is ok, then if I was doing the job with the light fitting you mentioned I would take a 1.5mm cable from the nearest ceiling rose or junction box, I would take it down to the switch, then take a 1.5mm cable to the ceiling light. In the back of the switch back box you would need to join the two neutrals(blue) together and the CPC(earth) I would connect the live(brown) feed in to the common and the the live out to the light into L1. In the light fitting the cables are installed as per the fitting connections. Perform insulation resistance and Zs tests at your light fitting and the last point on your circuit after completion. Run tests on your rcd or RCBO to check if it is operational and within the limits. This work does require a minor works certificate. Please feel free to ask any questions. If you aren’t competent or have the equipment to do the above then I would employ a registered and competent electrician.
