Outdoor RCD socket Trip

thepprentice · 23 Jun 2008

An outdoor door socket with inbuilt RCD i installed trips the CU RCD when the test button is pressed on the socket. both are rated at 30ma, but I would of thought that the test button on the socket should not trip the CU RCD, Does this mean its a faulty Socket/RCD?
Also if the RCD trips in normal use, should this trip the CU RCD, as its the same rating?

Cheers

holmslaw · 23 Jun 2008

Spark123 · 23 Jun 2008

It depends on how the trip button is connected, the normal RCD ones cause an imballance across L&N to trip the RCD. In this instance it should not trip downstream RCDs. However, unknowing how the manufacturer of your outdoor socket has connected the trip test I don't know. Some instances 2 30mA RCDs in series is unavoidable for example in caravan sites. Better to have 2 on an outdoor socket than none at all

thepprentice · 23 Jun 2008

cheers, i'll leave it as it is just incase

ebee · 23 Jun 2008

As the test button on some just connects ingoing ph to outgoing N via a resistance to pass about 30mA then both RCDs carry test current.
It is possible that both will trip as you have found.

As said not very good discrimanation, however as also stated then 2 is better than none.

Do you feel a bit safer being protected by 2 devices witth a possible 7% failure rate rather than just 1 such device?

TicklyT · 23 Jun 2008

ebee said:
As the test button on some just connects ingoing ph to outgoing N via a resistance to pass about 30mA then both RCDs carry test current.....

That setup shouldn't trip both RCDs . There would be no current imbalance either upstream or downstream of the device if the test button connected i/c phase to o/g neutral. the imbalance would just be at the local device.

If the test button connected a fairly high resistance earth to phase (or neutral) that would cause a current imbalance in the local device AND other devices upstream.

ebee · 23 Jun 2008

Of course you are correct

Spark123 · 24 Jun 2008

If it is connected phase to earth then that will create a dangerous situation should there be a break in the CPC and the test button pressed, the main reason we must test EFLI before conducting an RCD test
(was one of the questions in the C&G2391 exam - a lot of people got wrong

)

diynot

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Outdoor RCD socket Trip

holmslaw

Similar threads