Consumer Unit for TT Supply

[NealHarman]

Hi, have a TT supply, am in the middle of a complete rewire (part of extension/renovation) and need a new CU. Believe I need a 100mA time delay RCD as main incomer? Then 30mA RCD(s) where appropriate? Have seen a split RCD board from Rexel Senate but this is only 10 way (5+5) which is a bit small and inflexible. I guess we could have two, but what about a non split board with a main 100mA RCD and 30mA RCBO's for the circuit's that need them? Seems likely to be more or less comparable in cost to two split RCD boards.

Also, the current earth rod is about the size of a pencil and in poor condition, so needs replacing. I'm going to have to get someone in to do the CU, mainly because of the measuring earth resistance marlarky etc., which I'm not equipped to do - but in the meantime, I'd be happier replacing the rod and conductor. I read about 'choosing an appropriate rod for the conditions' but they only seem to commonly come in two sizes, so any reason not to just use the biggest one? Run conductor in conduit - any particular kind? You're supposed to put the head of the rod and clamp in an inspection chamber - TLC do an Earth Rod Terminal Cover, which I presume is what I want?

Regards and thanks,

Neal

 

[comms]

Try MK for the c/u, they do a 12 way split load with 100A 100mA T/D & 80A 30mA RDC's pre fitted. If you need more ways than that do as I have done, use MK 21 way c/u then install a split load kit & fit the appropriate rcd's.
If your going to run the main earth conductor in conduit, just use plastic/pvc type, & yes the terminal cover from TLC is what you are after.

 

[dw3101]

id just buy a normal split load, and ask wholesaler to swap 100a non rcd for a 100ma rcd... or just buy the 100ma on its own.

 

[ban-all-sheds]

The RCBO solution is better, and complies more closely with the regs, but it will cost more.

 

[plugwash]

if you are digging any big trenches for anything else then running a bare copper wire along the trench can be a good way of getting an earth electrode (this method tends to get better results than rods because it allows the electrode to be far longer)

recs use this method all the time though its not too common in domestic installs

if you do this make sure you use at least 16mm bare copper wire to reduce the risk of it getting cut through

 

[Damocles]

Have you noticed some RCBO seem to come in type C only?

 

[plugwash]

yep notably 1 module rcbos from the 3 electium brands volex wylex and crabtree.

thier 2 module rcbos are type B though