RCD - fault or not

[Paul.lythgoe]

I have carried out a rewire recently and installed a 17th edition split load board . All testing has been carried out and is satisfactory , including rcd test , the rcd test button works . The problem is whilst adjusting some wiring the neutral and earth touched together behind a light , I went to reset the rcd but it hadn't tripped , I checked the other circuits linking neutral and earth and the same thing the rcd doesn't trip. Anyone ever had this before?

 

[Andy™]

depends on the imbalance. could be normal. and this isnt exactly a questions for the forum sponsors either.

 

[a3]

Moved to Q&A

 

[NozSpark]

If you don't have any loads on any of the circuits protected by the RCD then a N-E short is unlikely to trip it.

 

[sparkytim]

+1

The RCD will only trip when it sees an imbalance of current flowing. If no current or very little is flowing then it won't, just shorting Nto E will not cause current to flow it will just divert some if it is already flowing due to a load drawing it at the time.

 

[batty]

If its TNCS it probably won't trip but generally TT or TNS it may that is what I find anyway.

 

[PC Electrics]

A N-E fault will only trip an RCD when sufficient current flows down the fault path to trip the RCD (usually around 25mA or so). For there to be a current flowing there must be equipment in use (kettle, lights etc etc). the value of the fault current flowing to earth will be dependant upon the relative values of the neutral return resistance and the fault path resistance and the current in use.

If nothing is in use, no current will flow and so no trip.

Draw the arrangement out and all will become clear.

 

[betty swollocks]

OP doesn't say whether the circuit was energised or not

The fact he was adjusting some wiring when the conductors touched sounds as though the circuit was dead in which case loading wouldn't be an issue for tripping rcd

 

[SPECIAL LOCATION]

I have carried out a rewire recently and installed a 17th edition split load board . All testing has been carried out and is satisfactory , including rcd test , the rcd test button works . The problem is whilst adjusting some wiring the neutral and earth touched together behind a light , I went to reset the rcd but it hadn't tripped , I checked the other circuits linking neutral and earth and the same thing the rcd doesn't trip. Anyone ever had this before?

Do you mean all the x1 x5 (@ 00 1800) all trip within correct times and x1/2 non trip is oall OK?

Or are you saying only the test button has been tested?

If all proper tests have been done as per pages 105 - 107 of OSG then I wouldn't worry.

 

[NozSpark]

OP doesn't say whether the circuit was energised or notThe fact he was adjusting some wiring when the conductors touched sounds as though the circuit was dead in which case loading wouldn't be an issue for tripping rcd

That would depend on how the OP isolated the circuit, if he turned if off using the MCB then a N-E connection on that circuit could trip the RCD if there is sufficient current flowing in other circuits protected by the same RCD.