# RCD Question



## TheRick (Apr 13, 2008)

stevie 101 said:


> Does an rcd operate on earth fault only or does it operate on short circuit too.? please help


 
Wasn't sure what an RCD was so I had to look it up.

Here is what Wikepedia says about them;



http://en.wikipedia.org/wiki/Residual-current_device#searchInput
A *residual current device* (*RCD*), or *residual current circuit breaker* (*RCCB*), is an electrical wiring device that disconnects a circuit whenever it detects that the electric current is not balanced between the phase ("hot") conductor and the neutral conductor. Such an imbalance is sometimes caused by current leakage through the body of a person who is grounded and accidentally touching the energized part of the circuit. A lethal shock can result from these conditions; RCDs are designed to disconnect quickly enough to mitigate the harm caused by such shocks.
In the United States and Canada, a residual current device is also known as a *ground fault circuit interrupter* (*GFCI*), *ground fault interrupter* (*GFI*) or an *appliance leakage current interrupter* (*ALCI*).

Hope this answers your question:whistling2:


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## Trimix-leccy (Dec 4, 2007)

RCD earth fault
MCB short circuit and overload
RCBO Earth fault and short circuit and overload

Job done:thumbsup:

....why do you need to know


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## chrisb271 (Jul 6, 2007)

And 9 times out of ten its a neutral earth fault that will trip the UK RCD's
Which is strange as the technical colleges will tell you that the neutral or return wire is dead and is at zero potential on pme systems,

I have had many a jolt off the neutral and can honestly say without any doubt they bl00dy hurt much more that a phase shock.

Chris


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## John (Jan 22, 2007)

This might help explain it.:whistling2:

View attachment 513


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## stevie 101 (May 29, 2008)

Trimix-leccy said:


> RCD earth fault
> MCB short circuit and overload
> RCBO Earth fault and short circuit and overload
> 
> ...


It came up in a college project and i couldn't find my notes. THANKS:thumbup:


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## stevie 101 (May 29, 2008)

chrisb271 said:


> And 9 times out of ten its a neutral earth fault that will trip the UK RCD's
> Which is strange as the technical colleges will tell you that the neutral or return wire is dead and is at zero potential on pme systems,
> 
> I have had many a jolt off the neutral and can honestly say without any doubt they bl00dy hurt much more that a phase shock.
> ...


I totally agree with the neutral jolt comment. Thanks for getting back to me:thumbup:


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## brian john (Mar 11, 2007)

Look at this. current is current if it does not pass through the sensor and exceeds the trip set point the GFP/RCD trips.


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