Conduit wire size

[maxhat]

I want to earth some new radiators, what size conduit wire do I need to use?

 

[mapj1]

This depends where the wire is to be run. If it is part of a bathroom equipotential bond (where you bond to all metal water pipes and the earth core of circuits feeding lights and showers etc -AT THE LOAD END, not the meter end! **) then 4mm if the conductor is exposed, or 2.5mm if protected against mechanical damage by trunking or conduit or similar.

If this is a main earth connection (services bonding to gas or water supplies) then 10 or 16mm may be required depending on the type of supply you have (TT/PME TNS etc.)
However if the radiators are not in a bathroom, and are not elsewhere bonded to the MET the most you need is the earthing already at the boiler itself.
If the pipes are plastic, or a plastic section for long enough to give a resistance of 22Kohms or more, then there is no need to bond at all.

Sorry to make it complex, but it is !
regards M.

** the intention is not to have well earthed radiators per-se but rather to ensure they cannot be at a different potential to a defective shower, whose case may actually be 50-100V above the external earth while a large fault current flows, if the earth impedance is high.

 

[ban-all-sheds]

the intention is not to have well earthed radiators per-se but rather to ensure they cannot be at a different potential to a defective shower, whose case may actually be 50-100V above the external earth while a large fault current flows, if the earth impedance is high.

I've never seen a shower with a metal case....

 

[mapj1]

I have however seen one that leaked live water down the tiled wall, while spraying the user with earthed water *, and the hoses are usually earthed on the better models with metal fittings.
In this case it may have been as well that the taps were not particularly well earthed.

M.


* and the comment was 'was that the tingling when you lean on the wall ? -Oh we could have had 3 dead bodies in the shower ! ' I don't know about you but I'd usually be reluctant to step into the cubicle over the first corpse....