On 10/12/2017 14:54, David wrote:
On Thu, 07 Dec 2017 09:51:24 +0000, John Rumm wrote:

On 07/12/2017 08:24, wrote:
Hi

Yes I think it is TN CS. This picture looks very much like my
installation

http://wiki.diyfaq.org.uk/index.php/File:PME1.jpg

So sounds like neutral and earth continuity is correct for my
installation.

N&E continuity (of some sort) is correct for the vast majority of
installations (assuming you are doing the test with the circuit
connected to the CU[1]). With TN-C-S the link is in your property. With
TN-S its back at a substation. With TT its via the general mass of the
earth, and may have a higher resistance, but is still good enough to
make a continuity test "pass" in many cases.


[1] If you want to test your "new" combined circuit in isolation, then
you need to disconnect it at the CU end and test there. That way you
will be free of the influences of the supply itself and any EQ bonding
connections.

This looks to be another advantage of RCBOs.

I had them fitted because I kept knocking the main breaker out with earth/
neutral contact when changing stuff.

Isolating both live and neutral can have advantages when you want to keep
most of the house powered up when you work on one circuit.

Take care with that though since most RCBOs are only single pole
switches (even if they are connected to neutral to allow for current
imbalance sensing). Hence they can't provide isolation of the circuit.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/