Down light help advice needed

plums1_2001 · Jan 18, 2014

Hello,

I purchased some bathroom down lights and the instructions advise they should be fitted with a double insulated, safety extra low voltage isolating transformer.

I purchased the following transformer type:
Knightsbridge T02 Transformer

[ElectriciansForums.net] Down light help advice needed

I have two problems,
should
Problem 1: The down light requires an earth yet the transformer does not. Should I run an earth cable to the down light?

Problem 2: The Down light requires Live, Neutral and Earth yet the two cables coming form the transformer do not stipulate which is the live and which is the neutral. The instructions dont either and the only info I can find is:
"output cable to the lamp 2 x 1.0mm2 silicon - min length 25cm, max length must not exceed 2 meters". I am unsure which cables coming from the transformer belong in the live & neutral on the down light.

Anyone come across this before? any advice appreciated.

Thanks

telectrix · Jan 18, 2014

the 2 wires from the transformer to the light can go either way. it does not matter which as long as they go to the lamp holder. earthing of the fitting should not be reqwuired. i would imagine that the fitting is designed for either 12V ( as you have) or with different lamp holder fitted for 230V. if in doubt, get a local electrician to fit them for you.

Richard Burns · Jan 18, 2014

Tel has the answer there, just make sure that the bulb connector is for a 12V bulb otherwise it will not work.
Some connectors for down lights have a built in earth cable but this would only be required for some 230V fittings.

plums1_2001 · Jan 18, 2014

Thanks for the advice! it is strange because the down lights state in capitals that they can not be connected directly to the mains (240V) but then why would it have an earth if it is going to be powered from a double insulated transformer? Would it cause a problem if I earthed them anyway?

Thanks again for your help :stuart:

telectrix · Jan 18, 2014

they are 12V SELV downlights. separated extra low voltage. look up the definition . if you ain't got access to BS7671, look in wickedpedia. specifically says " not connected to earth."

plums1_2001 · Jan 19, 2014

telectrix said:
they are 12V SELV downlights. separated extra low voltage. look up the definition . if you ain't got access to BS7671, look in wickedpedia. specifically says " not connected to earth."

Thanks for this although I cant find anything about them not being connected to earth. You are right they are Class III Luminaries and it states they should be connected to an SELV transformer only.

It also says in the instructions for the downlights:

connect to terminal block: Blue to neutral, brown to live and earth where appropriate..

Logic tells me that if the downlight is being powered by a double insulated transformer (12v) then it shouldn't need to be earthed.

This was going to be straight forward but the fact that they included an earthing option on the downlight itself has confused me.

Thanks again for your help.