Confused, must be missing something simple.

[trev]

Right, the way it read was that you'd just inserted the earth pin. Like I said when I first stuck my oar into this, socket testers ain't the best mate I only trust them for circuit tracing really, anything important and out comes the MFT.

 

[Octopus]

I didn't expect anything. The socket tester was in one side of the double socket and I inserted the plug into the other. As the earth prong made contact the tester changed. This I found interesting and don't know why it would alter the live/neutral reverse light.

I should also say the MCB had tripped a number of times which is why I was called and I was trying to determine whether the hob or cooker was part of the problem, which is why I was inserting the plug.

My MFT will "suggest" L-N reverse if there isn't an earth connection.

Matey next time, whip out your MFT and do a couple of proper tests.....

 

[davesparks]

You don't even need the MFT to check the polarity, the Approved voltage indicator that you have with you at all times for safe isolation will be fine

 

[Flanders]

Live and Neutral reversed. However the cooker circuit was an immersion heater circuit originally 2.5mm T+E. The board was fine, but the supply to the cooker was in red and black cable from the board, however in the cooker switch it was brown and blue. So a connection of sorts was made when new kitchen was installed and tiled over. The oven and hob are both gas so the cooker switch is only operating the igniters.

As an aside and I get what people have said about the socket tester, why does it light up as if the circuit is correct when an earth prong of a plug is inserted into one side of a double socket?

Tester in one socket shows a live neutral reverse and then an earth only prong is inserted into the other socket of the same two gang plate and then tester shows no fault.

If you are plugging an appliance into the circuit and it is turned on it will give you a link from live to neutral, this may be what your plug in tester is seeing coursing your plug in tester to give you a false reading, Just a thought i may be wrong

 

[Octopus]

You don't even need the MFT to check the polarity, the Approved voltage indicator that you have with you at all times for safe isolation will be fine

True, but often its just as easy to use the MFT and do a Zs at the same time!

 

[Richard Burns]

The tester would indicate line neutral reverse if the line and earth were at the same potential and the neutral was significantly different. If the socket had an unconnected earth and this earth was partially connected via a high resistance to line then the tester would see line and earth at the same potential and neutral at zero.
You plugging in, say, the gas hob ignition plug earth pin (and if the hob is bonded via the gas to earth) then you would have just earthed the socket and the voltage on the earth would then be discharged, the high resistance joint would prevent a short (but may be low enough to trip an RCD) and then the potentials on neutral and earth would be equal (ish) and the line at 230V.
Perhaps.