Earthing Problem?

[monty2229]

Hi Guys,

First post here and I am encountering a very weird issue I havent seen before and am struggling to work out.

I recently did a few upgrades at a home including a new DB and earth stake. The home is split with half power run under the home and half power and lighting run above the home ceiling. The old earthing system is a bare wire system.

My issue is that when I connect the upstairs earthing system to the new earthing arrangement I am seeing some very weird issues. On the power circuits run above the ceiling I am seeing:

A-E - 0V
A-E - 240V
N-E - 240V

I have tried disconnecting the neutral to the circuit at the board to confirm the earth isn’t joined to the neutral somewhere and I still get the same readings. If I test that earth at the board against A, B and C phase I only get 240V which confirms that it is not connected on one of the other phases also.

I tried running a new tail from the earth bar up to the ceiling space and joining it onto the old earth system and still the same issue.

The earthing system for the rest of the power circuits are working fine.

The lighting circuits are encountering the same issue. I have checked the polarity on all sockets too.

All circuits are on RCBO.

Could anyone shed some light on what it could possibly be or any tests to try niggle this issue out as I’m a little stumped?

 

[pc1966]

Sounds like live and neutral swapped somewhere in the light circuit. Do you have a long "wander lead" to check the phase & neutral connections from upstairs back to the board?
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Of course, it might be worse and your upstairs earth is connected to the live/phase!

Again, using a wander lead you could check it is low enough resistance to the main earth terminal.
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If you don't have a wander lead, then kill the power with all breakers (but leave the main supply on, assuming you have single-pole breakers and all-pole main isolation switch/RCD), check that everything is dead, then check the resistance for N-E and A-E upstairs. You should see a complete open for A-E and either a short for N-E (if TN-C-S / TN-S supply) or a moderate resistance for the earth rod in a TT supply.
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Then open the main switch and repeat, now the N-E and A-E should be completely isolated.

If, as I suspect, you still see A & E together then an open E and then some accidental short A-E could explain it, normally it should trip the breaker to disconnect such a fault.

If you now see both are open then it looks like an A / N swap.

 

[Instantsafe]

Might pay to check the water pipes as well.
The old cast iron or copper water pipes are usually connected to get a decent earth connection... but then someone cuts a section of pipe out, and/or replaces it with poly prop, and that section of metal pipe does wonderful things to the circuits. Conversely if a live terminal is shorting to a water pipe... this may show up elsewhere!