4 pole RCD

Mark.W · Nov 27, 2012

Hi chaps

Having quite a heated discussion with a colleague about a 4 pole RCD. He originally installed a 30mA RCD which now needs to be changed to a 100mA, however the N is on the opposite side. He seems to think that putting L1 into N of the RCD, L2 into L1, L3 into L2 and Neutral into L3 would be ok, and the RCD would still work.

What are your thoughts?!

Cheers
Mark

44ALLAN · Nov 27, 2012

Mark.W said:
Hi chaps

Having quite a heated discussion with a colleague about a 4 pole RCD. He originally installed a 30mA RCD which now needs to be changed to a 100mA, however the N is on the opposite side. He seems to think that putting L1 into N of the RCD, L2 into L1, L3 into L2 and Neutral into L3 would be ok, and the RCD would still work.

What are your thoughts?!

Cheers
Mark

The test resistor is normally across 1 phase and neutral so if you satisfied that it would work/if you didn't and picked up 2 phases ! BANG lol...........why someone would contemplate putting a ~Live into a Neutral connection is another matter !!!!!!

snowhead · Nov 27, 2012

This is a Wylex 4 pole, as long as the neutral was at one or other end it would work, but each make may be different;

Darkwood · Nov 27, 2012

What a numpty i hope said bloke isnt an electrician as hes an embarrasment to the trade, and please dont tell me he qualified too :90:, you entertain the idea of fitting live terminals to connections marked N, it may work on brands with 4pole disconnection but will simply contravene the regs as you havent followed manufacturers instructions. At worse you could create a potentially very dangerous situation.

Darkwood · Nov 27, 2012

Here's one that would go bang if you pressed the test button if you wired as your mate suggested, to note the test button is wired across 1ph and N so changing this set-up as suggested would put 400v through the test resistor and blowing it.

44ALLAN · Nov 27, 2012

Interesting the different set ups for the test buttons on the wylex ( across 2 phases ) and the one you've highlighted.
My 4 pole rcd's have the test button between L3 on the input side and Neutral on the output.
That's to facilitate using it as a 2 pole device if you want to........wiring to L3 and Neutral only which would still allow the test button to work without the need for an external resistor

Darkwood · Nov 27, 2012

It highlights the various designs and hopefully the OP will take this in for his defense in his heated debate but anyone not wiring as designed by manufacturers is a bit of a bodgit and scarper regardless of whether it might function on some models, had they pre-empted the N position then they could have ordered the correct one in the first place rather than trying to cover their mistakes by cutting corners.

Mark.W · Nov 27, 2012

Thanks guys! Exactly what I thought! I think he got the message!

Darkwood · Nov 27, 2012

Does that mean hes on here then? or did you just pass on my comments

Mark.W · Nov 27, 2012

Haha! I passed on your message!

Darkwood · Nov 27, 2012

Print off the example images we put up on this thread as they back our comments up, he isnt incorrect that it can be done but it would contravene regs and is only applicable to certain models of 4p-rcd's but to preach this to you without further explaining the points we have shown you here is shortsighted and poor judgement, so i can only assume he actually believed what he was telling you to be correct across the board.

Engineer54 · Nov 28, 2012

There is also the possibility that the neutral line has a different switching mechanism to the phase lines, which is not shown on the diagrams... Crazy to connect a phase line to a terminal clearly marked with an N!! lol!!

markc123 · Nov 28, 2012

I've seen many 2pole RCD's wired opposite which isn't so bad because its just a switch.....granted still bad practice and potentially dangerous and anything installed should comply with the manufacture's instructions and/or the regs. But to wire a 4pole RCD wrong is just plain stupidity. Charge a capacitor and throw it at his face.

Knobhead · Nov 28, 2012

If it were 4 pole then it would be OK, if it’s 3 pole and neutral it wouldn’t. 3p+N the neutral is late break, early make.
As for the voltage of the test circuit, they allow plenty of leeway in the resistor tolerance so highly unlikely to cause damage. If the RCD is working correctly the test disconnects with it opening. I.E. mili seconds, no time for it to burn out.

Darkwood · Nov 28, 2012

I Quote from Schneider Tech' data sheet with regards to their 4pole rcd unit -
Nominal voltage - 415v
Test button operation voltage - 115v to 264v
(They also do a mgv 4p range with test button voltage of 112 - 456 just to clarify it only effects certain rangers)
Sending 400v across the test button only rated to 264v could damage it to a point it fails or could give a false positive reply when the rcd is actually faulty (it trips even though the rcd may not be functioning correctly) so if you haven't got a meter to check this then you may assume its ok -i.e. the customer doing a quarterly check.

So in this particular case il stand by my responses that you shouldn't swap N with a L even if you discarded the regulation re' following manufacturers instruction which does over-rule the argument anyway.