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Discuss TT earth, Dual RCD or RCBO and Main Switch in the Electrical Forum area at ElectriciansForums.net

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I have a replacement consumer unit coming upon which is currently off a TT system with a nice low reading on the earth. There is no chance of the DNO converting to TNCS. No SPD or AFDD as per client.

I intend fitting a new Dual RCD consumer unit.

I have researched this site and there was talk of the main switch being swapped out for a 100mA time delayed RCD. Albeit as I understand all this will protect is the internal wiring from the main switch to the RCDs. The use of the glands and cleating of mains tails would reduce the chance of any damage.

1/ I am led to believe that a dual RCD board would not protect all the circuits.

2/ I believe that a dual RCD would be permissible and would not lose any protection even if one RCD was to trip.

My questions are which is correct 1 or 2, i believe its 1, secondly would you still replace the main switch with a time delayed RCD.

Thanks in advance.
 
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Wilko

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Hi - provided there are no “high integrity” circuits connected prior to the RCDs then no need for 100mA time delay RCD upfront, in my view. Glands and clamps yes by all means.
 

Ian1981

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Mentor
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Regulation 531.3.5.3.2.201 is what you need to consider
 

Wilko

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So do the manufacturers internal links have reinforced insulation?
Not that I’ve seen ... but I’m hoping to be corrected :) .
I have seen twin RCD CU with rigid internal conductors which should reduce the risk if one screw was to come loose.
 
  • Thread Starter Thread Starter
  • #6
Guys I have sorted this now. The internal wiring on consumer units between main switch and RCDs is fine as long as the manufacturers cables are used. You also have to ensure the mains tails are in a gland and are cleated which I do anyway.
 
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