Rcd protection

[Nobby Clarke]

Ringmain fed by 32A mcb on split board protected by rcd,I'm spurring of ring feeding a underfloor heating system rated at 9A ,I know I can fit a d/p 13a fcu,but do you think its overkill if I fit a d/p 13A rcd fused spur so the heating system has it's own rcd protection ,so it will switch off on fault without losing power to ringmain.

 

[Dustydazzler]

No need for the additional rcd spur , a normal spur will be fine

 

[Dartlec]

The issue with adding an RCD spur is that there's no guarantee that would trip before the main one, even if the fault were on the UFH (assuming both are 30mA) so it might just complicate fault finding or lead to both tripping anyway...

You could put a 10mA one on for the UFH I guess, but if everything is OK the RCD should not be tripping with any regularity anyway so I wouldn't bother and just go with a good quality FCU.

9A. that's a BIG UFH mat isn't it?

 

[Mikegh]

Do you get discrimination with a 10ma, I think you maybe do at less than half of 30

Not much point though you risk creating a nuisance using the 10 on the ufh

 

[telectrix]

the Mersey will flow backwards before you can be sure which RCD will trip.

 

[Mikegh]

the Mersey will flow backwards before you can be sure which RCD will trip.

You're right there sorry