This is a good'un!!!!

[danspark12345]

So.

Went to test RCD with MFT at the socket. My meter alarmed and said reverse polarity. I then checked the connections, they were correct.

I then put my little plug in tester in and it showed something was wrong but doesn't say what. (Look at picture).

Baffled. I then check polarity at the board and the meter. All good.

I plugged my plug in tester into all sockets in the house. I had the same warning in every socket. This tells me the problem is upstream. But everything seems fine

 

[old_guy]

Is it possible all sockets have LN switched at the terminals?

 

[Rockingit]

I'm rashly assuming that you've checked the incoming tails at the CU aren't reversed?

 

[littlespark]

That’s the only bit we can’t visually check…. Meter to cu.

You can trace from the cutout fuse to meter… and from mainswitch to rcd within the board.


From the supply side of the mainswitch, what voltages do you get L-E and N-E?

 

[brianmoooore]

Have you had a non contact tester (Voltstick) against the wires? That will show if reversed at cut out.

 

[danspark12345]

I'm rashly assuming that you've checked the incoming tails at the CU aren't reversed?

I have yeah

 

[danspark12345]

That’s the only bit we can’t visually check…. Meter to cu.

You can trace from the cutout fuse to meter… and from mainswitch to rcd within the board.


From the supply side of the mainswitch, what voltages do you get L-E and N-E?

L-E 240v N-E 0V

 

[danspark12345]

Is it possible all sockets have LN switched at the terminals?

Checked them

 

[ferg]

Is it only the sockets or are other circuits affected?
If it's only the sockets I'd be looking for a junction box very close to board.

 

[littlespark]

Possible false reading on the tester?

Do you have an MFT that does the same test

 

[old_guy]

So.

Went to test RCD with MFT at the socket. My meter alarmed and said reverse polarity. I then checked the connections, they were correct.

I then put my little plug in tester in and it showed something was wrong but doesn't say what. (Look at picture).

Baffled. I then check polarity at the board and the meter. All good.

I plugged my plug in tester into all sockets in the house. I had the same warning in every socket. This tells me the problem is upstream. But everything seems fine

Are the neutral legs going back to the correct neutral bar?

 

[UKMeterman]

Try using a wonder lead on a spike into the ground, measure the voltage between the spike and L N and E of the supply.

 

[Teddy Lop]

What did you use for polarity at the CU, same instrument? Will the RCD test at the CU? whats the ze and zn at the CU?

 

[Rockingit]

This is where a decent long wander lead pays for itself!! However - correctly done fig8 tests should also reveal an issue on an RFC (which I'm again, rashly, assuming is the case?). Use a plug in socket adaptor and a long lead back to the board and simple continuity tests will narrow this down before your cuppa's gone cold.

 

[newfutile]

I had a case like this where all the sockets (keyswitch) were wired L-N reverse from the manufacturer (we think).
In this case if polarity is correct at the Consumer Unit a wander lead can be used to check L N E at each socket to the disconnected Consumer Unit cables