Intermittent Time Delay Rcd Failure

Had a pretty nasty fault at a caravan site. New caravan being put in place so the installers pulled out the hook up post (using a Land Rover or tractor I suspect) - and in doing so pulled the SWA sheath out of its gland - so live insulation cut through by the gland. Still earth contact on outside of gland. Should have tripped the Time Delay RCD at the distribution unit but didn't. This meant all the earths became live. Scary!

Intriguingly when I switched off the RCD (before finding the fault) the RCD wouldn't reset. After fixing the fault the RCD reset and trip times were OK - but the first two times I tried the test button it didn't work.

This was a Denmans Basics RCD. Has anyone ever experienced anything similar? If anything had happened who would have been responsible?

Bet they had not tested it quarterly   ( and kept a record), like the sticker & instructions say  

I fitted it less than 3 months before - and all working properly at the time.

Surely if it was a direct L-E fault should it not have taken out the Mcb at supply never mind the RCD?

No - as a caravan site avoiding TNCS - so all TT - Ze 56 ohms so not enough to trip the MCB.

Yes quite correct Dave, brain not synchronising with what eyes are reading!

All I say..... If a RCD fails then it FAILS...

You won't get a second chance in the real world

NozSpark said:

All I say..... If a RCD fails then it FAILS...

You won't get a second chance in the real world

Click to expand...

Seconded.