RCD issue

[Podooser]

It is a TT supply. The 30mA RCD when I test it isolated from the final circuits it serves, the results are as I would expect for a new RCD. If I then connect up the ring and test the RCD at a socket using the plug in adapter, the RCD fails (1 times is > 300mS) . Why should that happen, am I missing something?

 

[Spark123]

What else is plugged in?

 

[Adam_151]

Unplug everything and try again,

If the device isn't tripping at all then its possible there is a faulty/badly designed appliance preventing it from tripping properly (rogue switchmode powersupplies, televisions, motor speed controllers, etc)

If it does actually trip then an applicance could be holding up a dc voltage... fooling the tester into reporting a longer trip time (anything with a capacitor in it, or a universal motor)

 

[Podooser]

Thanks Adam. I will double check to see if there is anything plugged in but I was sure there was nothing. If it is an appliance should they remove it permenantly. By the way it fails on the 5 times as well.

 

[Adam_151]

Is this a situation where you have done a full set of tests, or just an RCD replacement... if teh former then isyour IR ok for the rfc? (one would hope that that would show up the majority of forgotten applicances!*)

*though if you are not sure if you've missed any or not, do it on 250v as a pre-test... less destructive

 

[Podooser]

Full set of tests. IR for P/N is low (25M?), others fine. Why should a very low IR between P/N that does not trip the RCD under normal conditions fail the RCD whilst doing a 1 times test.[/wiki]

 

[Adam_151]

Full set of tests. IR for P/N is low (25M?), others fine. Why should a very low IR between P/N that does not trip the RCD under normal conditions fail the RCD whilst doing a 1 times test.[/wiki]

It doesn't , it does mean however that there could possibily be a piece of equipment connected that you don't know about thats playing silly beggers with the RCD

Does the RCD trip on the integeral test button with the rfc energised, and sorry, you are still not clear, when your tester reports a fail value, has the RCD actually physically tripped or not?

 

[Podooser]

My tester (Metrel) does not trip the RCD at all, it stops the test process once it gets to 300ms and says fail >300ms.

 

[securespark]

I have Metrel Alphatek.

You have to test RCD direct from outgoing terms with neutral disconnected & MCB's OFF.

If it works OK like that, it's something in the circuit giving the tester the run-around.

 

[Spark123]

Ask a daft question, is the RCD definately protecting these circuits?

 

[Podooser]

I have Metrel Alphatek.

You have to test RCD direct from outgoing terms with neutral disconnected & MCB's OFF.

If it works OK like that, it's something in the circuit giving the tester the run-around.

I have tested it direct and it passes fine. something in the circuit like what...

Spark yes it is these circuits.

 

[securespark]

An appliance.

Why not disconnect everything & megger the circuit using method 2?