Earthing Cut From Lighting Circuit.

I'm not a spark mate but it would seem to me if all the fittings are class 2 (including the b-room fitting), which I take to mean plastic, and there aint no earth, then I don't really see how you could bond the light ctt. anyway. If the rest of the install is fully rcd protected, supp. bond isn't required.

Can't you maybe crimp on some extra earth wire and reconnect the earths in the lighting ctt.?

Will be interested in other replies.

 

Like I say mate, my "academic" take on it would that if the light fitting is class 2 it won't be able to introduce any kind of fault as it's not extraneous, so I can't see how bonding it will make any difference. It's not like a there will be a voltage difference between it and any extraneous metal parts in the event of a fault.

 

Sounds like you don't fully understand how an rcd works? The leakage to cause the imbalance doesn't necessarily have to be to the circuit earth, any earthed object will cause the rcd to operate, no need for any earth connection to the supply earth.

 

The RCD will still provide additional protection...The RCD will operate when it detects an imbalance between line and neutral. Say it did had a metal light switch, no CPC in the circuit, line conductor shorts to metal light switch, you touch the light switch whilst touching a radiator that's connected to earth somehow through a parallel path such as the bonding or boiler circuit CPC then you will be part of the earth path....In which case the RCD operates as it detects the imbalance. For me if the circuit has no CPC, all fittings/accessories are class 2, circuit is protected by a 30mA RCD as it enters a special location, warning notice on board stating not to fit class 1 fittings then it's a C3.

 

The issue you have here is not the rcd, it's do you need supp. bonding in the b-room.

 

All fittings are class 2, being class 2 they are not exposed conductive parts. The purpose of supplementary bonding would be to limit touch voltage under fault conditions between exposed and extraneous conductive parts. If there is main equipotential bonding to extraneous conductive parts such as incoming services(water and gas) and all circuits supplying the bathroom or circuits passing through zones of the bathroom are protected by a 30mA RCD then no supplementary bonding is not required. The C3 would be for the lack of CPC which doesn't comply with the requirements of ADS.

The method of fault protection for that particular circuit is the fact the fittings/accessories are class 2.

 

I'm DIY and happy to be corrected, but I think the "to earth" part of that isn't needed!
It's just inbalances between the phase conductors.

As I say... happy to be corrected!

Regards,

Cando

 

Indeed. I would expect the RCD to operate regardless of the bonding being there, or not. Not sure why @leesparkykent has used such an analogy as to suggest the rcd would not operate in the light switch without an earth if it was touched, regardless of touching an extraneous part simultaneously.

 

Correct.

 

An "imbalance" is all that is needed to operate the RCD.( forget about earths per se for a moment)
Which is why in split RCD boards...crossed neutrals will cause tripping.
Having said that....neutral is in fact a hard earth.
So the discussion is more about logical semantics .
RS

 

As well as in a TT system?

 

Firstly, the CPC should not be cut out, regulations require a CPC to all outlets unless in a I.T. earth free installation, which this is not. These earth conductors must be re instated and connected.
The bonding, assuming the pipework is not plastic and is not electrically continuous copper, bond to the bath taps, sink taps, shower and radiator. Take the bonding lead to the nearest available earthing point, perhaps the shower switch. If the light fitting is enclosed in conductive material and can be touched when also touching other exposed metalwork, then it must also be part of the bonding system.

 

yep,....at source the centre tap on the star winding is sent out as a N..(with one phase)....decked hard at the same time.
The rod in the consumers installation is the return path to the centre tap.
RS

 

A single phase RCD must measure the same current in the neutral that went out through the phase, if not, then it is fair to assume that some of the current has leaked away somewhere, this is called an earth fault. If the level of leakage current, and hence the difference between phase and neutral currents exceeds the tripping current(30mA is common) the RCD will operate and disconnect the faulty circuit. As RS has pointed out, in a split board the neutral must pass back through the RCD that the phase came through, otherwise the RCD will trip. Apart from this the regulations insist that the neutral shall be connected to the corresponding way an the board as the phase, so use phase terminal 3, then you must use neutral terminal 3, observe this Reg and all will be well on the RCD front.

 

At one time all lighting was without CPCs.
You could purchase T&E without the E.
Where T&E was used, the E was generally cut off at the terminations.
Where existing installations have been wired without a lighting CPC, one of the options is to ensure all fittings and accessories are class II provide the circuit(s) with RCD protection and place a warning label at the CU not to use class I fittings and accessories.