Ceiling Lights

[jonesy73]

Lady Jones wants new chandelier style lighting in the living room. The new lights have three wires, and an extra earth from the suport clamp. Whilst there are only two wires from the house.

Live and Neutral - Not a problem! But what do I do with the earths? Do I connect them together? Or, do they both need connecting to the metal clamp that's attached to the ceiling joist?

 

[ban-all-sheds]

What do the instructions say?

From your description I would say that both the light and the clamp should be connected to the circuit earth. Where you join them is up to you, as long as you do a proper join, e.g. choc-block, and don't just twist them together.

 

[jonesy73]

Thanks for the advice!

I'm sorry to come across as a complete wilf, but are you saying that the Light Earth and the Clamp Earth should be joined together, or do I need to "create" Circuit Earth into the main wiring??

As for the instructions. Made in the UK, but instructions in a very strange language.

 

[ban-all-sheds]

You need to connect both the light and the clamp to the earth in the main wiring.

 

[breezer]

the way i read it he has no incoming earth to connect to.

Jonsey73 is that right, you only have 2 wires in the ceiling red / black?

 

[ban-all-sheds]

B*gg*r me - you're right. Why did I not read that too?

 

[breezer]

B*gg*r me -

no thanks

 

[jonesy73]

Holy Moly!!! This is getting XXX rated


Breezer is right there are two wires, black and red.

Sheds - Don't beat yourself up. You're dealing with a novice, who'll gladly tinker with a car but is still trying to understand the bricks and mortar side of life!

 

[securespark]

I'll pass up the offer of sex, thanks guys!

If there is no earth, there are three options:

(i) replace your fitting with a double insulated one (no earth connection required)

(ii) install a single earth wire from the fusebox, but this is tricky, as it should be run in close proximity to the live.

(iii) rewire!!

 

[jonesy73]

Thanks for the replies! This weekend will be an adventure into home electrics.

 

[ban-all-sheds]

I'll pass up the offer of sex, thanks guys!

If there is no earth, there are three options:

(i) replace your fitting with a double insulated one (no earth connection required)

(ii) install a single earth wire from the fusebox, but this is tricky, as it should be run in close proximity to the live.

(iii) rewire!!

(iv) check to see that it's not simply that some bandit has cut the earth core right back - it may be that all you need to do is to cut back a bit more of the outer sheath.

 

[brown-nought]

(iv) check to see that it's not simply that some bandit has cut the earth core right back - it may be that all you need to do is to cut back a bit more of the outer sheath.

Excellent point, however I'm sure Ban would also tell you to do a continuity test. You need to ensure the earth cable goes somewhere. If its not conected in one fitting I guarantee it won't be the only only missing link.

Bottom line never assume - test.

 

[securespark]

Ban's always showing me up. Bl*ody amateur.....!

 

[dingbat]

Excellent point, however I'm sure Ban would also tell you to do a continuity test. You need to ensure the earth cable goes somewhere.

This [very good] advice has been repeated several times recently, but without an explanation of how it can be done. Although you should ideally have properly calibrated equipment you can test the continuity of a cpc ('earth') conductor in a circuit by disconnecting the cicuit from the supply, connecting together the 'earth' and live conductors at the consumer unit, then checking with a continuity tester between live and 'earth' at each point of utilisation (lighting point). You should do this test with all the lamps removed and all the switches closed ('on').

What you are doing, in fact, is checking that [should a live/earth fault occur] a low resistance circuit exists that will cause the circuit protective device (fuse or MCB) to operate. The reason this is important is that, otherwise, it would be possible for metal parts of a light fitting to become live in the event of a fault and simply sit there, at line potential (230V), waiting for you to provide a personal path to earth!!

Actually, while writing all this it dawns on me that although most people understand the idea of a two-wire electrical circuit, even hardened sparks get confused when it comes to the subject of earthing/bonding. Maybe Mr Prescott is right and we need protecting from ourselves?

 

[plugwash]

the normal method of protection from indirect contact in normal environments is EEBADS

Earthed
Equipotential
Bonding with
Automatic
Disconnection of
Supply

Earthed :the system must be tied to earth

Equipotential
Bonding : stuff that could carry a potential in and out of an equipotential zone must be bonded together so that in the event of something becoming live everything stays at more or less the same potential (within bathrooms where this is more critical we make the equipotential zone one room for normal protection the whole house is treated as one big equipotential zone)

Automatic
Disconnection of
Supply: enough current must flow such that in the event of a short between a phase conductor and the earth protecting it the cuircuit will be disconnected rapidly (exactly how rapidly depends on other conditions but with type B mcbs this is irrelevent anyway)


there are other systems possible ofc like earth free equipotential bonding but theese need to be carefully designed to be safe