Myself and my Boss were having a rather lively argument yesterday over a submersible pump. I certified a place recently where there was such a pump down 130 metres into the bore. This pump-head is a 3-phase unit (230V) and has an Earth wire on it as well. All the connections are hermetically sealed on it. OK then, could someone please explain why it is required in my Boss's view that this pump be protected by a 4 Pole RCD @ 30mA. Sure it is for a domestic water supply out in the rural parts of Canterbury, but there are lots of places here that don't have them (RCD's I mean). What is your take on this?.
Hi Kiwi, Yeah, I was wondering that myself. I have never seen an external circuit to a house, such as a water or waste-water pump protected via an RCD. Outside garden lighting where the lamps can be accessed yes, but something that is usually only accessible to competent persons, no. Next thing being, this pump does not have a neutral (being 400V 3-Phase), so how would the RCD detect a leakage from Phase(s) to the required neutral?. Even all the controls (Pressure switch, etc) are 400V. I must say, I've never struck this problem before. Same side of the coin, ever seen the price of a 3-phase RCD before?, they aren't cheap.
RCD have been invented to check for earth leakages.
A false connection to the neutral is a partial or total short circuit. It can be detected by overcurrent protecting devices or more sophisticated current/power observing electronic devices. But never by an RCD.
Whether with or without neutral, an RCD will work as well, except for the test button. The way of connecting with correct test button function to such systems is often written on the device itself.
Price: So what is it down under?? In Germany we start with 25 € as said above.