TT - Consumer Tails Protection

LmarshallSparks · Friday at 7:32 PM

Quick question, Do TT earthing systems consumer tails require RCD protection?

I believe they do, but I rarely see them on short tails? Does it only apply when the tails are over three meter?

Thanks for any help electrical masters

westward10 · Friday at 7:59 PM

If they are over 3m then they will need circuit protection, ADS would apply therefore RCD protection is almost certainly required.

LmarshallSparks · Friday at 8:00 PM

westward10 said:
If they are over 3m then they will need circuit protection, ADS would apply therefore RCD protection is almost certainly required.

Westward as always you’re a hero! Can you point me to a regulation about why at 3m they require protection? Why not 2 or 4?

So shorter tails (less than 3 meters) do not require protection? Still a good idea though?

PS Electrics · Saturday at 10:39 AM

LmarshallSparks said:
Quick question, Do TT earthing systems consumer tails require RCD protection?

I believe they do, but I rarely see them on short tails? Does it only apply when the tails are over three meter?

Thanks for any help electrical masters

There was an article on this suggesting RCD protection can be omitted where all outgoing circuits are protected by an RCD/RCBO providing suitable measures are in place. The tails need to be protected and supported by means of a Tails Clamp, Tail Gland and suitable support outside the enclosure. The meter tails should be stripped back only the amount which is required for termination into the main switch and not a dual RCD board (tails within dual RCD consumer units between the main switch and the RCDs are normally only single insulated cable)

RCDs, metal consumer units and TT installations | NAPIT

NAPIT's Bill Allan answers another common contractor query. Contractors sometimes ask whether it's necessary to install an RCD in a TT installation before a metal consumer unit (i.e. a 'front end' RCD

professional-electrician.com

mainline · Saturday at 3:34 PM

LmarshallSparks said:
Westward as always you’re a hero! Can you point me to a regulation about why at 3m they require protection? Why not 2 or 4?

So shorter tails (less than 3 meters) do not require protection? Still a good idea though?

434.3

434.2.1
(i) not exceed 3 m in length.

Some DNO's stipulate a maximum of 2 mtrs.