bonding baths

[RMS]

Hi,

BS7671 states that metal baths do not require supplementary bonding unless they are connected to a structural part of the building, ie. steel girder.

My company require all metal baths to be bonded regardless of this which is fine. How does everyone elso go about this? Do others bond baths excluding the above information?

I understand that metal waste pipes are required to be bonded etc. They way i look at it is that the bath is either connected to other extranious conductive parts, ie. taps or its isolated. Any thoughts?

RMS

 

[ban-all-sheds]

A metal bath can be an extraneous-conductive-part.

It can be an e-c-p through being fixed to structural steel, or being supplied by metal pipes or having a metal waste.

Whatever the reason, if it's an e-c-p it should be bonded.

If it's not an e-c-p then bonding it makes it more dangerous, not less.

 

[RMS]

So if the waste is plastic and the taps have plastic/rubber washers either side hence no connection to an other e-c-p then bonding would make the installation more dangerous?

RMS

 

[Adam_151]

In that case I wouldn't bond it, even if the rubber washers were poor insulators (accumulation of dirt around them, etc), its only going to float to the potential of the bonding unless you make a circuit through it causing a voltage gradient across the grime resister... and whats it going to make a circuit to in a bathroom when everything that had a potential has bond potential?

Do however consider the bath could be a ECP if sat on a concrete floor

 

[Spark123]

I agree with adam, if you are unsure if an item is an ecp a measurement can be obtained between the item and the MET, iirc there is some info in GN5 on this. There is also some additional info here;
http://www.iee.org/Publish/WireRegs/EarthingPlasticPipes.pdf

 

[ebee]

what if cables are run near the bath ie behind the panels on top of the floorboards would not supp bonding guard against fotuetous contact?
If you make the bathroom a "Faraday" cage?
Faraday cage = named after Michael er ohh forgotten His last name now!
Anyway Michael something or other who invented the Faraday cage - He was a clever fellah

 

[Softus]

Surely any Faraday Cage is simply an illustration of a naturally occurring phenomenon that Michael Thingy discovered, not something that he invented?

 

[ebee]

I stand corrected.
Issac newton invented gravity but have we conclusive proof he was not Greek?

 

[JohnD]

I think the cage is an invention, an application of the effect which he discovered.



It's very lucky that Newton invented gravity in time for plenty of it to be manufactured and shipped to Australia to save all those convicts dropping off the underside of the world.

 

[ban-all-sheds]

If you make the bathroom a "Faraday" cage?

Why would you want to stop all electromagnetic radiation entering or leaving the room?

Some people like to listen to the radio when they are in the bath, for example....

 

[Softus]

I think the cage is an invention, an application of the effect which he discovered.

Some Googling reveals that I'm probably wrong on both counts:

1. The Faraday Cage of lore is indeed an invention.
2. Faraday didn't discover the relevant effect; more likely it was Carl Gauss, but even more likely than that it was Francesco Beccaria.

Why would you want to stop all electromagnetic radiation entering or leaving the room?

I don't suppose anyone would, but isn't the concept at play here the one of distribution of charge, rather than EMF/RF filtering (even though the latter is also an effect of deploying a Faraday Cage)?

 

[JohnD]

My tempest-shielded bathroom is where I keep the PC for doing my classified work on

 

[plugwash]

there is no need to make the bathroom a faraday cage, the voltages involved in domestic mains wiring are low enough that non-contact effects are negligable. The aim is simply to prevent any points that have an impedance low enough to cause dangerous shock to anything outside the bathroom are held at the same potential.

 

[RF Lighting]

My tempest-shielded bathroom is where I keep the PC for doing my classified work on

I hope you are powering that with an isolating transformer

 

[JohnD]

Generator driven by non-metallic shaft through the mesh from a motor outside.

No phone or networks connections.

Earth-free zone.

No metal pipes.