On Aug 27, 4:04*pm, "ARWadsworth"
wrote:
For some reason I can hear Baldrick saying "I have a cunning plan"

He went to work on the breakup of the electricity network in the
UK :-)

OP:
If your supply is TN-C-S (PME) the limit is 0.35ohms however the
measurement tools have quite a substantial error when you get down
that far, never mind the test lead contact resistance. It would only
become an issue if the figure rose sufficiently high at the furthest
point on your install to mean a circuit breaker will not disconnect on
a L-E fault within a reasonable time (which is about 0.4sec). Thus
that is not a concern.

There is a Wiki / uk.d-i-y FAQ on RCD tripping. Basically unplug
everything (not just turn off), then see if the RCD trips.

If you have a split-load RCD system you may want to create a dual RCD
setup (RCD1 RCD2) or convert to split load, or convert to a couple of
RCBO thereby (say) keeping lights (up & hall) and one power circuit on
(cooker) if the main RCD trips out.

RCDs will trip on N-E faults - damp socket, screw touching a cable,
trapped cable in a floorboard, water penetration into an external
circuit, or on L-E faults such as failing immersion element, kettle
element, heater element, washing machine or dryer or cooker element,
clothes iron, even microwaves are not unknown.

If you do buy an IR tester from say Ebay to test each cable
individually, you need to ensure any burglar alarm & smoke alarm is
disconnected, along with all other appliances. Neon's will give fake
low IR (eg, 0.67megohm) so they need to be out of circuit (fuse out or
turned off).