I have bought an ELCB and a mini DB board for a small solar/inverter project. My understanding is that an ELCB trips when there is a potential difference between earth and neutral. The diagrams I've seen online all show an earth connection to the ELCB, for example:

Thanks electrical-engineering-portal.com

However, when I try to connect up my ELCB, I can only see the four main connections (live and neutral, in and out). Here, pics:


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There are no other connections apart from those four. How is the ELCB earthed?

The only way I can think of is through the connection to the metal rail on which all the breakers are installed. However, the backing of the breaker does not seem to be conductive.


1 Answer 1


The Onesto KRC3 is a residual current circuit breaker and these types of devices operate by measuring a difference current flowing in live and neutral rather than specifically measuring a leakage current to ground.

ONESTO KRC3 230/240V 25A 300mA KRC3 Residual Current Device Leakage protector Circuit breaker

The above description is taken from here

The difference between live and neutral currents IS earth current in effect: -

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As you can see from the above, EARTH is included but isn't needed and some devices down provide a thru-going connection for earth at all. In north America they are called ground fault circuit interrupters: -

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