Plastic pipe, composite sink, earth?

[R D S]

The answer must be, you don't, surely, obviously?

But i've replaced a sink and some pipework, none of it is metal, i'm looking at the earth that was strapped to the copper and assuming I do away with it...

[spuorgelgoog]

Depends.

Is it (or should it be) main equipotential bonding to the incoming water main, which should be reconnected to the incoming water main (if metal)?

If it's supplementary installed by Kenny Kitchenbodger, or a council electrician who bond everything, it can be done away with in a kitchen.

Supplementary bonding is required in bathrooms *if* not all circuits are RCD protected.

Owain

[John Rumm]

Yup.

When you say "earth", what do you actually mean though?

Supplimentarty equipotential bonding, does not actually require connection to the house earthing system (even if it often gets it indirectly anyway). Its just there to limit any possible exposure high touch voltages. The logic is you treat the bathroom as an equipotential zone, and decide what things are capable of bringing a potential into that zone from "outside" (even if that potential is earth potential), then electrically tie those things together.

So a ceramic basin connected via all plastic pipes, is not capable of bringing a potential into the zone, and so does not get included in the supplementary equipotential zone.

Copper radiator pipes however may, and so those should be connected (although that can be out of sight just outside the room if desired). The rad itself can't on its own bring in a voltage, so that is not bonded.

[newshound]

It won't do any harm though to bond it back to the nearest socket in the ring main. I did that once to get rid of a "tingle" from a steel sink. Nothing tripped the RCD and everything passed a megger test, never figured out where the electrons were coming from.

[Chris Green]

That's not bonding! It might also be argued that it's not a good idea to create large chunks of earthed rather than floating metalwork as it makes it easier to kill yourself by touching something live *and* something earthed.

[Brian Gaff (Sofa)]

Electrostatic charging is a very odd thing sometimes. I remember a friends house where one felt a tingle off of the taps, but not the sink. Looking underneath it was all plastic pipe. Weird. Brian

[Adam Funk]

green & yellow wire!

[John Rumm]

:-)

That's kind of what I was getting at...

Just because its Green and Yellow, does not make it an earth. (Its one of the reasons they call them "Circuit Protective Conductors" or CPCs, and not "Earths" in the techno speak).

They are used for both earthing and equipotential bonding, which are different systems designed to do different things in different ways.

See:

[Roger Hayter]

So are all the criteria for equipotential bonding met if there are no earthed metal electrical appliances and no metalwork connected to an extraneous earth in the room, i.e. the equipotential bonding is floating with a high impedance to earth? I suppose it doesn't happen very often.

[John Rumm]

Supplementary bonding can be totally isolated from the main premises earth, and it will still function as intended. (Since sticking you hands to two bits of adjacent metalwork, both live at 240V due to a fault won't give you a shock so long as you have no access to anything at earth potential).

One of the tests for identifying if an extraneous conductive thing needs to be included in the eqipotential bonding is to measure its impedance to the main earthing terminal.

(note to be classed as "extraneous conductive" it also needs to be Conductive, not a normal part of the electrical system, and capable of bringing a potential into the equipotential zone)

No, not often - just the presence of the main equipotential bonds will usually mean that the systems end up being connected.

[newshound]

Sorry, bad terminology, but I'd still argue it is better to have a metal sink tied back to a good earth in those circumstances. I'm reasonably confident that *my* accessible live sources are protected by RCDs. I'd assumed the sink was acquiring its AC potential (I forget the value, and it was obviously high impedance) from some external source, perhaps via my damp walls (built straight on the limestone underneath). And it was definitely AC, not some sort of funny static as described by Brian.

[Fredxx]

You are free to argue, but it's not current practice.