RCD, ELCB, RCBOs

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Thread Starter

kgh2378

Hi Guy's

I know this may seem a bit of a too basic question for this forum but bare with me as it is still above your average wire jerker's knowledge.

Will an RCD still work without a Neutral/Earth Combo when IT Earthing is used? As a Marine Electrician I've always learn't NO it won't. If this is indeed the case then why not?

I once experimented on a vessel that had some installed with an RCD tester and the RCD's wouldn't trip until 50mA which is over the safe shock threshold, but even then I was told that the testing unit did not fully emulate a real life electric shock synario.

Thanks in advance & Merry Xmas
 
M

mikearnold007

hi guys

An RCD measures the difference between the outgoing current and return current which should be zero. So if I understand you correctly the unit must have a neutral connection.
 
> An RCD measures the difference between the outgoing current
> and return current which should be zero. So if I understand
> you correctly the unit must have a neutral connection.

No that's the whole point. There is no Neutral connection with IT earthing. Just phase to phase connections. Most commonly 220v or 440v. The idea being that an accidental connection from Phase to Earth e.g. loose wire, will not trip the circuit breaker and allow the offending equipment to run until such time that it can be safely switched off and repaired.

However if you put an RCD on such a circuit then you would still be measuring 0v on the trip coil under normal conditions but what about under fault conditions when there is no return path to transformer or generator?

I can confirm that you still get more than tickle when you come in contact with said power source.
 
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