"Johnny Boy" wrote in message
...
Hi

I've installed a new kitchen sink and have put supplemental bonding from
the incoming cold water
pipe across to the hot water pipe and also to the sink. The regs don't
require this but I can
see no harm in it, and it reinstates the position before the works on the
kitchen. I wonder why
this was dropped from the regs?


An electrically conductive (metal) appliance that can be touched, or can
come into contact with a live supply conductor, even due to a fault
condition such as damaged insulation, should always be bonded to an earthing
point. That hasn't changed.


I also noted that the main bonding from the water pipe to the block
adjacent the CU is 6mm.sq
not the 10mm.sq that the 16th ed. specifies. I condsider that there's no
need to uprate this to
10mm.sq since the regs are not retrospective. Also it would be almost
impossible physically
without taking the wire round the outside of the house! Again, I wonder
what was the rationale
for the change?


The bonding to that point may be created in 6mm csa cable, but is the
bonding to the actual mains water supply pipework the same. From the mains
electrical supply, the bond must be created in 10mm csa conductors, but any
further supplimental bonding can be reduced to as low as a 1mm csa
conductor, totally depending on what rating of fault current is expected on
that particular part of the circuits. That hasn't changed.

Finally, I know it's been done a while back on previous threads but what
's the view re 2.5mm.sq
unfused spurs from 2.5mm.sq ring mains (Type B CB at 32A). My personal
view is that it's not
acceptable on grounds of cable rating - but it used to be allowed. Anyone
know why this
changed?


Many times it had been found after serious electrical fire incidents, that
the occupants had connected large loads to circuits which had been added to
the mains ring supply by smaller gauge conductors and so causing them to
form overload condition in that particular section of cable. So this meant
that the requirements had to be changed in the form of which methods were
used in making tapped circuits only take the current rated for that
particular section of cable.

Therefore, if a spurred circuit is supplied with a cable of 2.5mm csa, then
this spur should be restricted by the use of an automatic breaker between it
and the rest of the ring mains supply and which only allows that section of
cable to take its maximum load rating. Connected this way, the spurred
section is not allowed to rely only on the mains ring breaker back in the
consumer unit to stop it going into overload condition and failing. This
bit has changed from the old requirements, but many, many years ago.


Regards
Jx




---
www.basecuritysystems.no-ip.com

Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.535 / Virus Database: 330 - Release Date: 01/11/03