Old RCD reg?

Paul.M · Mar 7, 2011

Something that I've never come across. RCD connected to the MET bar with a cream wire.

Can someone explain the theory for this? Earthing arrangements for combined protective and functional purpose. I can't seem to get my head round how this would work. Only thing I've come up with is that that rcd is connected to line and earth only and monitors discrepancy to earth and not N.

SirKit Breaker · Mar 7, 2011

I've seen it, in an old MEM board i think it was, but never gave it much thought. Has it got a BS number? must be something like a RCBO.

Cheers...........Howard

tony mc · Mar 7, 2011

I took one of these out last week with a earth fly lead I will see if its in the van and get any numbers off it. I remember it was quite big took up about 4 ways in the old CU.

Andyfm · Mar 7, 2011

MEM still use them in their boards

MarkieSparkie · Mar 7, 2011

This is an electronic RCD which requires an earth reference for the phase detectors in the electronic circuit to detect the out of balance condition, similar to most RCBOs, unlike the more common toroidal current transformer type RCD. The usual reason for using electronics is to reduce the physical size of the RCD package or to speed up the operation of the device.

tony mc · Mar 7, 2011

It is a MEM but has the following numbers on it BS 4293 BS 5419 BSEN 61008 BSEN 60947-3 !!!

It is a normal size RCD got it mixed up with another one starting with a Y funny french thing!!!

keefy · Mar 8, 2011

Its the way the MEM RCD's work so I have been told. The fly lead assists in the workings, or summit like that! If it has a BS EN no its not that old.

Paul.M · Mar 8, 2011

Thanks MarkieSparkie and Tony, never came across one before and now I know. Cheers lads I'll research this next week when I have more time.

Ps tony is that a past paper or a testing explanation sheet in the top right hand corner? Thanks for taking the time out of your revisions. Good luck.