Instantaneous shower


Postby ROBERT.PARKER » Wed Mar 25, 2009 12:15 pm

What would happen if a live supply accidentally touched the neutral terminal on a properly earthed instantaneous electric shower?
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Postby rosebery » Wed Mar 25, 2009 7:52 pm

The RCD would pop.

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Postby Dave From Leeds » Thu Mar 26, 2009 11:29 am

And the water would go cold!
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Postby plumbbob » Thu Mar 26, 2009 9:17 pm

Sorry to have a different opinion here, but I would suggest the RCD may not necessarily trip as there is no earth leak.

I would suggest there would be a big bang, the fuse or trip in the consumer unit would disconnect the feed and the water would stop flowing.

For sure, no one should be electrocuted if that is what is on your mind.
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Postby rosebery » Fri Mar 27, 2009 7:13 am

Thje RCD should pop as there will be an imbalance betwen the "live" and "neutral". These potentials which should be equal and this is what the RCD monitors. Earth leakage is only one condition where such an imbalance can occur.

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Postby plumbbob » Fri Mar 27, 2009 7:36 pm

But isn't that the point? There is no phase / neutral imbalance in a short circuit. The current carried by each of the two conductors will be equal so the RCD will not activate.

RCD's normally fitted to domestic consumer unit's don't offer overcurrent protection either. For that, a RCBO is required.

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Bob
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Postby rosebery » Sat Mar 28, 2009 10:18 am

"There is no phase / neutral imbalance in a short circuit"

Yes of course - your right - wasn't thinking straight.

"RCD's normally fitted to domestic consumer unit's don't offer overcurrent protection either. For that, a RCBO is required."

But an RCBO is an RCD (RCD being a generic term and RCBO being a specific example of an RCD/MCB combined). I assume an RCBO for a shower circuit anyway in which case it will pop surely.

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