Chrome light - no earth?

[Nijinski001]

I have just uncovered a chrome light fitting and discovered that the lighting system has no earth. The previous occupant of the property has linked the earth for the light fitting to the neutral cable coming into the fitting?????

Is this normal practice?

Is there any way of earthing the fitting without having to run an earthing cable back to the fuse box?

 

[Adam_151]

Replace the twin with twin and earth, if you can't do this immediatly, at least remove the link to the neutral

 

[Nijinski001]

Will remove the link...... actually already have.

What if the whole lighting circuit has no earth?
Is it possible to earth the fitting anywhere else?

 

[kendor]

you may not have to earth the fitting anyway, just because it has a chrome surface it may still be double insulated ie the holder is double insulated from the body of the lamp check to see if it has a double insulated symbol.
In saying that you really should have an earth system on your lighting circuit regardless even if there is no need to connect it to the appliance.

 

[ban-all-sheds]

If there really is no earth on the lighting circuit, then you can't use any light fittings that need an earth, or any metal switches.

You can't earth them elsewhere, and a circuit with no earth indicates an installation of an age where a full inspection is called for.

To say nothing of it previously being in the hands of someone who would connect neutral to the earth terminal of an appliance...

 

[Nijinski001]

Thanks guys.
The 'common practice' comment about the Neutral/Earth bridge was tongue in cheek obviously!!

This isn't my house it belongs to a friend who happened to call me in 'cos he thought he had a problem witha light fitting. Turns out he didn't have the problem he thought he had but a bigger one instead.

The house is to be rented and has recently undergone some re-furbishment including a loft conversion. The builders had some numpty head wire in the light fittings. What the f*** was he thinking bridging the earth and neutral!!!! He had effectively rendered the light fitting as a neutral conductor. Before I was aware of a problem I touched the light fitting, obviously gave it the earth it lacked and tripped the circuit. Lucky me eh!!

My friends question was "will it be okay without an earth?" and "do I have to spend more money?" and "what's the worst case scenario if I don't?"
Answer 1 - Er... no!!!
Answer 2 Er..... yes!!!!
Answer 3 Errrrrr.......... DEATH!!!

Step 2 - Further investigations reveal the lighting circuit IS earthed. Most of the liight fittings are chrome or brass and only two are void of earthing cables. The fittings are not DI.

Step 3 - put in new cables from the main circuit to the two fittings.

Step 4 - Try to find the builder who did the work and make sure he knows what his numpty head did!!!

By the way, I'm part Pd so he can spend the money on me instead of another dodgy builder.

 

[plugwash]

To say nothing of it previously being in the hands of someone who would connect neutral to the earth terminal of an appliance...

this was common practice in some countries at some times (apparently its common in older east german wiring) and its possible the person came from there.

Its a double edged sword doing this, it protects you from faults in the appliance but it leaves a very very nasty hazard should the neutral core in the fixed wiring break.

 

[Nijinski001]

So that explains it. The builder's numpty head was probably and immigrant of some sort?

Does this not mean though that the whole light fitting becomes part of the circuit and therefore an exposed conductor?
Is that not then dangerous if within reach?
What part of 16th Ed would clarify this?

 

[slippyr4]

Before I was aware of a problem I touched the light fitting, obviously gave it the earth it lacked and tripped the circuit. Lucky me eh!!

Why did that happen? Neutral to Earth via a human shouldn't generate enough fault current to trip an MCB. Are the lights on an RCD? And i'd be suprised if you could get 30mA through you from a neutral.

Or did it lack a working neutral too?

 

[Nijinski001]

The plot thickens.

No RCD just a plug in MCB that tripped.

Just going back a stage...... which is more dangerous, no earth or bridged earth/neutral?

 

[plugwash]

if you tripped an MCB i think its far more likely that you knocked it in such a way that two bare wires touched.

btw if you find missing earths anywhere then you should check all earthing!

 

[plugwash]

which is more dangerous, no earth or bridged earth/neutral?

It depends on the situation

the problem with using a current carrying conductor for your earth is if said current carrying conductor were to break then the item will become live.

the problem with no earth (or an inadequate earth) is if a bare wire touched the inside of the item then the item will become live.

basically both allow a single fault to make the item dangerous, which is worse depends on the relative likelyhood of the two faults which depends on the nature of the installation.

metal case class 2 (double insulated) appliances have all mains connections inside insulated so it would take two faults (connection in contact with case and connection insulation damaged) to create a hazard

utility service wiring that uses combined neutral and earth has the CNE (combined neutral and earth) completely surrounding the live so its basically impossible to completely break the CNE core without also breaking the live.