Rings main Resistance with MCB off

jimbobaroobob · Jul 10, 2013

Hello there
I have a query, I'm sure I'm missing something obvious.
Changing a double socket today (no faults with the old one, just changing from white to brushed steel).
I Kept the mains switch and RCD in the 'on' position and just isolated the relevant ring main using the MCB.
Before disconnecting anything, I always check there is no voltage at the outlet using my meter.
When I went on live to earth as normal, rather than setting AC volts, I had left my meter on resistance and it showed low resistance.
Is this a normal configuration?
I used my 'plug in' socket tester before and after and all green lights. Any existing faults would have tripped the RCD.
I could check the wiring by disconnecting from the CU and doing an Insulation test if necessary.
Many thanks

Darkwood · Jul 10, 2013

You are measuring load resistance on anything plugged in you still have Earth commoned to N on the DNO's side so you are effectively reading a L/N load connected / plugged in. Drop out both Neutral and Earth connections in the board and you shouldn't get any reading between L/E on the ohms range. As you have already pointed out you only disconnected live.

To note here you should have done a full test on the circuit and this would include total isolation from the board to ensure you don't get parallel paths this would have given you the opportunity to see the circuit was sound with no curious readings.... and why haven't you already done an insulation test ... even though you are doing something as simple as changing like for like you still should be ensuring the circuit is fully tested to ensure when you have done you are not walking away leaving an existing issue/danger.