Question about my lights, and funny earth ????

[richard1600]

Please see attached, drawing of the setup i have discovered.


Bathroom, heater cupboard, dining room.

3x lights,
3x switches,
Emersion/boast heater
Earth’s

All 3 lights are on the same circuit breaker. The 2 bathroom lights have 3 cables going to each, the dining room light has 2 cables. Each light is individually switched.
3 earth cables all go to the same point connected to a normal light switch along its rail. (Picture above).

What is this earth point all about (not connected across switch, its connected on the rail)?

What sort of layout is going on here for the 2 bathroom lights to have 3 cables going to each?

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• richard1600
• 12 Aug 2011
• 1

 

[ban-all-sheds]

I'm struggling to understand what you mean.

What's a "rail"?

The reason that some of the lights have 3 cables is that they are loop in, loop out and switch.

I'm very surprised that someone who is an electrical and electronic engineer, who has studied electricity for many years and has spent a long time learning regs and how household electrics should be done, and has carried out substantial rewiring jobs has never encountered the most common form of lighting circuit there is.

//www.diynot.com/wiki/electrics:lighting

 

[richard1600]

my work does not involve household electrics, i am not a sparky or i wouldnt be on here,

the main question is, there are 3 earth wires shown in the picture,,, they all go to the common rail on the back of a standard light switch..

it looks like somsort of junction for earths to be connected as they are not connected across the switch.. is this a normal way of connecting earths???

please please please dont start all this again ban all sheds, i am not a sparky at all,. i am currently studying for my BsC in electrics and electronical engineering, my work has been mainly large electronic control systems,, not household electrics, hence i am here asking these questions,

 

[Spark123]

Could be something to do with local supplementary equipotential bonding?

 

[richard1600]

ok,, what does that mean, lol.

 

[Spark123]

//www.diynot.com/wiki/electrics:supplementary-equipotential-bonding

 

[richard1600]

ahh i see,

thanks very much.. makes sense, but why would a standard on/off switch be used to join these earths together,,, especially as none of the cables are connected to the swtich, is there not some sort of purpose built junction box or something in order to achive this ???

 

[ban-all-sheds]

the main question is, there are 3 earth wires shown in the picture,,, they all go to the common rail on the back of a standard light switch..

Light switches don't have a "common rail". Do you mean the terminal(s) marked COM?

it looks like somsort of junction for earths to be connected as they are not connected across the switch.. is this a normal way of connecting earths???

Thought you said they were connected to the common rail on the back of the switch?

please please please dont start all this again ban all sheds, i am not a sparky at all,. i am currently studying for my BsC in electrics and electronical engineering, my work has been mainly large electronic control systems,, not household electrics, hence i am here asking these questions,

i was told about 17th edition, what i want to know is, what exactly do i need to have to work as an electrican-household. and how do i go about getting it, am hoping i dont have to sit through courses etc, rather just do some revision and take some exams, as the knowledge is already there...

i removed all wiring and connections, and sockets and everything including the kitchen sink and i have rewired everything brand new as per regs, and all is certified. i am an electical and electronical engineer and have studied electricity for many years,
no i am not a "sparky" thus had to spend along time learning regs and how household electrics should be done, which has all been checked and certified by qualified electrican. (he inspected in stages and gave advice)

basically have an old house and am aware that the wiring is not to 17th edt regs...
.
.
what i want to do is rewire the lot with new distribution boxes and get signed off,,,

 

[richard1600]

Ban_All_Sheds...

No need to be so arrogant.... i am asking for advice. like i said, am not an electrician.

let me load a picture so you can see...

If you look, the earths are not connected across the switch itself, rather connected along a "RAIL". i dont know what else it is called if it is not some sort of connecting rail. much like a commom mode bus-bar i would assume...

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• richard1600
• 12 Aug 2011
• 1

 

[JohnW2]

let me load a picture so you can see... If you look, the earths are not connected across the switch itself, rather connected along a "RAIL". i dont know what else it is called if it is not some sort of connecting rail. much like a commom mode bus-bar i would assume...

As you've said, in some senses it's being used as a 'junction box'. As has been suggested, it's quite likely that at least one of those earth wires is 'supplementary bonding' - if that's the case, it has to be connected to your electrical installation's CPCs ('earths') somewhere, and this is as good a place as anywhere else. As well as being a means of joining together earth wires, that 'rail' also serves the purpose of connecting the back box (if metal) to earth, via the fixing screws, even if the box is not explicitly connected to earth (which it should be).

What is wrong in what you've said is that the switch in the picture is not a 'standard light switch' - what does it control?

Kind Regards, John.

 

[richard1600]

Thanks very much indeed,

i was not sure why there would be a swtich there at all, i mean it doesnt need a switch as nothing is connected to the switch part itself...

the box is also earthed yes.... best to leave alone then ??

or is there another type of box that will do the same job but without a switch on it ???

thx again

 

[richard1600]

This is the front of the switch..

would it not be better to just have a blank front ?
as nothing is connected to the switch part anyway?

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• richard1600
• 12 Aug 2011
• 1

 

[JohnW2]

Thanks very much indeed,
i was not sure why there would be a swtich there at all, i mean it doesnt need a switch as nothing is connected to the switch part itself...
the box is also earthed yes.... best to leave alone then ??
or is there another type of box that will do the same job but without a switch on it ???

Oh, I see - so it is literally being used just as a 'junction box'. Maybe the switch once had a purpose, but no longer - or maybe the person who installed it didin't have a blank plate to hand!

If the switch itself isn't being used, you could simply replace it with a 'blank plate' and use some sort of connector block to join the earth wires.

Kind Regards, John.

 

[richard1600]

Thanks john, very helpful. question answered.

 

[JohnW2]

Thanks john, very helpful. question answered.

You're welcome.

Kind Regards, John.