On Tue, 01 Feb 2005 12:23:39 +0000, Alan wrote:


Can I common up netural and earth in the CU?? I've yet to see what
voltage is between them but last time I looked a few years back it was
only a few volts.

On an aside, the reason there's a few volts there is due to the the
impedance of a fairly hefty neutral core in the street supply cable
between the consumers and the substation.

It might be a few volts, but if you provide a second path for the neutral
current to return to the transformer (via the ground) then proportion of
that current[1] will be diverted via your earth and your common joint.
That's going to get hot. Also, if your neutral suffers a fault further up
the line you're in danger of everything in your house rising to some
undesireable voltage.

There are types of supply earth where something like this is done but the
suppliers know what they are doing more than you or me ;-/ And they design
it work in that way.

[1] Not just your current, but any other neutral current in your area will
back feed to your earth bond)

Timbo