Bathroom earthing

[HiZ]

Well im sure its not the first time its been asked (yes ive searched the forums). If only the rules were clear.. some people say they are and all of a sudden a forum thread turns into 5 pages long.... says it all really!

Just refitting bathroom suite and moving a central heating towel rail. Also installed a zone 2 compatible metal mirror cabinet/shaver outlet unit. Zone 2 also has an IP44 240v lighting bar (metal) with 5 spots.

On a joist above the bathroom is a JB, here the upstairs lighting cable stops off before looping through each of the ceiling roses in the bedrooms. All done in 1.5mm.

Bathroom light and cord switch simply replaced the old horrible stuff. Currently I have connected the mirror cabinet in 1.5 and used the T&E earth back to the JB. I plan to earth the towel rail water supplies and bath/sink water supplies with some 6mm and take this up to the JB. Does the mirror cabinet need a sperate earth in addition to the one in the T&E. Not sure what it would add as it would end up at the same place.

A spark told me it is not practicle to terminate the supplimentry earth in the type of ceiling light I have, very tight... hence the JB just next to it.
Does the supplimentry bond need to be one long contiunious conductor? No plastic fittings or pipe used. Compression and push fit copper only.

Can of worms here we come.....

Cheers.

 

[sm1thson]

Not sure what it would add as it would end up at the same place.

#they end up in the same place but when theres a current flowing that means they will be at different potentials.

eg. a fault causes 240v to go onto the cold water pipe in another part of the house, the cold water pipe should be bonded at the CU so will be 0V here so in between (ie in the bathroom) it could be anywhere inbetween (eg 100v). the hot water pipe will be bonded elsewhere so it wil be at 0V (no current flowing) so if you are touching them both when a fault happens the current will go throu you! (as you will have 100v in one hand 0v in another)-if you tie them together they are at the same potential (voltage) so it doesnt go through you!

-thats (one reason) why it should all be bonded together at the bathroom.

http://www.niceic.org.uk/downloads/NL139supp.pdf -shows how it should be done.

 

[HiZ]

What size earth cable shall I use?

4mm or 6mm?

 

[Spark123]

Do you have an electric shower and if so, what size earth wire to it is there in there?

 

[HiZ]

No electric shower

 

[Spark123]

As long as you don't have anything else with a big power supply in there 4mm is adequate. Are your hot / cold / radiator pipes metal? If so these need bonded too.

 

[HiZ]

cheers.

All pipework is metal.

Im more concerned about earthing the metal mirror cabinet/shaver outlet. I was going to take the bonding back to the JB in thr loft... which is where the mirror/shaver supply/earth is connected to anyway.

 

[Spark123]

Providing there is a bonding conductor between the earth wire for each circuit supplying equipment in the zones and to metallic pipework etc of the bathrooms it is fine. Theres a picture in this document showing what is required (you need to look at the one for metal pipe installation on p3) http://www.iee.org/Publish/WireRegs/EarthingPlasticPipes.pdf