Isolation switch help ? I

[Hundleton1]

I have a quick question, I have my part p inspection on Friday, I have changed my CU as my competed job for inspection as it needed doing anyway however I have one question.

I fitted a split board, it came with one isolation switch and one RCD, I am on a TT system so I wanted full protection and changed the isolation switch for a second RCD, now I have set if up with the first RCD looking after light up and sockets down and the second RCD with the opposite bit with the shower added to that.

Now as I have done this I don't have a one main isolation switch on the board, to isolate everything you have to turn off both RCD's, is this ok?

I have checked the regs and all it states is circuits must have a method of isolation that it double pole Whitchurch my RCS's are

 

[Hundleton1]

Also sorry about the spelling I have posted this from my phone

 

[JUD]

AFAIK you still need a main switch as a single point of isolation for the entire installation. (537.1.4)

Didn't you have enough room in the board to just add the second RCD instead of replacing the Main Switch?

Or better still, why didn't you buy a 17th Ed board? Sounds like you've fitted a 16th.

 

[sparkdog]

I did the same and fitted an external mains switch next to the cu.

 

[martysparky]

I was thinking that new tails to isolation switch.

 

[mogga]

sounds like 17th CU meant for use with circuits not requiring rcds and those that do require rcd protection beleive it or not not every instalation requires total rcd protection

as for changing the main sw for an RDC you havent got discrimination so realy defeated the point in fitting 2 RCDS ie Your First RCD is likley to trip at same time as the second one

 

[Hundleton1]

sounds like 17th CU meant for use with circuits not requiring rcds and those that do require rcd protection beleive it or not not every instalation requires total rcd protection

as for changing the main sw for an RDC you havent got discrimination so realy defeated the point in fitting 2 RCDS ie Your First RCD is likley to trip at same time as the second one

looks like you rite the board was setup for split load with some not rcd protected, when i added the second rcd i spotted the discrimination problem so i set it up so that both RCD were fed from the meter tails rather than one feed from the other.

the meter tails come into the first RCD then are looped out to the second RCD with the supplied internal cables, the unit has 2 separate neutral bars so it was straight forward to do, however i have this isolation problem as i previously mentioned, iv just had another look and i have room for a switch as well (just) but i will need some more internal cables, i will also have to move the bottom live bar over a bit as well,

if i add the isolation switch then feed both RCD's of that with 4 internal cables (2 l & 2 N) that should be fine ?

 

[GStueyXR]

Fit an external contractors isolator

 

[Guest123]

I would say it'll probably be easier to install an external isolator as the lads have suggested.

Just make sure you point out to your assessor that you have re-configured the CU in order to provide discrimination.

 

[mccant]

why didnt you just fit a board with a main switch and dual rcds you can pic em up for £50 ,i would have fit this and a seperate 100mA isolator before the board, because of your tt system. make sure the ze and zs are acceptable

 

[JUD]

why didnt you just fit a board with a main switch and dual rcds you can pic em up for £50 ,i would have fit this and a seperate 100mA isolator before the board, because of your tt system. make sure the ze and zs are acceptable

No need for 100mA if all circuits are protected by 30mA (as in a 17th Ed Dual RCD)

 

[mccant]

the 100mA main isolator before the board to reach your dissconection time, as i said check your ze- zs values . remember regs are guidance common sense is much more important

 

[JulianC]

the 100mA main isolator before the board to reach your dissconection time, as i said check your ze- zs values . remember regs are guidance common sense is much more important

As JUD says, dual 30mA RCDs in a 17th ed. board will achieve this.

I am more impressed that the OP's predictive text thinks 'which' is 'Whitchurch'

 

[GStueyXR]

I am more impressed that the OP's predictive text thinks 'which' is 'Whitchurch'

LOL, missed that

 

[Guest123]

As he's on a TT system, only if the DB was metalclad would a 100mA TD RCD be needed between the meter and the DB.