RCD problems..

[davesparks]

Sounds very similar to the problem I had too , faulty circuits would not allow rcd to trip , and when I tested with circuits isolated at the DB , found I couldn't get any readings and would not trip , Test button works o/k though , I came to the conclusion that the RCD has become faulty over a period of time with the faulty circuits connected and continuously reset against the fault ,the whole lot was quite old anyway....

Did you test with all outgoing cables disconnected from the RCD, or did you just switch off MCBs/remove fuses?

 

[Piratepete]

i don't know why, either, but i've come across it a couple of times. once was on a dual RCD CU, where neither RCD would trip, not on the test button or x1 and x5. dissed the radial with a N fault and RCDs then tested perfectly.

What bothers me about this, is that you have a situation here where the RCD is unlikely to trip in case of a real fault e.g Electric iron goes live and client dies.
OP says the test button works (see page 2), so the client will have no idea that it may not trip in practice.

I've just been doing an EICR on a domestic where a ring had a low N/E IR (not low enough to trip the RCD) but the RCD (Eaton) still tested OK. I find the reliance on RCDs worrying. Perhaps it was a bit premature to do away with supplimentary bonding!

 

[Leesparkykent]

RCD tests should be carried out with the outgoing conductors disconnected. Just turning the MCBs off is not enough, unless the MCBs are double pole then this would be acceptable.

With the N-E fault present the test current which normally flows to earth will partially flow through the N-E fault and return via the neutral conductor. With that ridiculously high Ra very little of the test current will actually flow to earth.

I totally agree with this. One of the issues contributing to this is the high RA with the neutral offering less resistance than the earth.

 

[Plonker 3]

agree but current needs to flow in cpc to create imbalance,with no load connected and cpc and N short rcd wont trip but will with button because that is internal through resistor

What if someone grabs a live cable, will that not cause the RCD to trip too?

 

[kenny7askew]

What if someone grabs a live cable, will that not cause the RCD to trip too?

course it will,the person provides the earth route

 

[telectrix]

it should, dilb, but i'm only likely to try that if i feel suicidal.

 

[Leesparkykent]

it should, dilb, but i'm only likely to try that if i feel suicidal.

Like if you owned that metrel from the pic last night? Lol

 

[telectrix]

yeah. it's even uglier than the yellow peril fluke.

 

[HappyHippyDad]

course it will,the person provides the earth route

I think Dillb probably knows that Kenny... and that was the point.

 

[telectrix]

if this forum was south park, we could kill kenny.

 

[Des 56]

course it will,the person provides the earth route

He may own an expensive pair of wellies

 

[telectrix]

He may own an expensive pair of wellies

for the leisure centre? ( 2 sheep in a field)