TT Board

[Jonnyboy 68]

hi all

Just replaced an old CU installation with a 17th edition board and installed earth rod & pit etc ... enjoyed it .. my first TT and all's gone well !!! The board I installed was 12 way split 5+5+2. I intended to use the two unprotected ways for the smoke alarms and a dedicated fridge/freezer circuit in case of nuisance tripping. However being my first TT, I've re-read my regs and they state that ALL circuits on a TT have to be RCD protected ??? I've done my reading and therefore wanna use a 100mA RCD 'S Type' as my incoming main switch ... this is ok ?? However, I have QVS and TLC around here but only TLC seem to do a Wylex 100mA time delayed RCD and it's a bit steep at

 

[Sidewinder]

Price for 100mA S is about right or there abouts.

Come back on the rest later, sorry, got to dash

 

[Lee321]

can't all your circuits go on the 30ma splits?

opps just re-read

but does your cable/depths allow for non rcd?

 

[Andy™]

2x RCBO may be cheaper

 

[Marc]

but does your cable/depths allow for non rcd?

Not on a TT. ray

 

[Andy™]

Not on a TT. ray

OP wants 100mA RCD. i think lostit was asking if they are exempt from a 30mA RCD (i.e not chased into a wall), and so suitable for 100mA TD

 

[Lee321]

[quote name='Andy

 

[ElectekAir]

[quote name='Andy

 

[sparkytim]

+1

Use 30 m A RCBOs and leave main switch

 

[batty]

You cannot Rcd main switch as this will not comply with 17th because if you have a fault on any off the two circuits you will lose all your power which is why you have two RCD's in board.

 

[Lee321]

batty he was going to fit a higher rated rcd to give discrim

 

[Andy™]

batty he was going to fit a higher rated rcd to give discrim

and a fault on the circuit only on 100mA TD???

it would be fine if there was a fault thats on one of the 30mA RCD's

 

[batty]

batty he was going to fit a higher rated rcd to give discrim

But if you have a neutral to earth or live to earth fault it is going to trip everything off.

 

[Lee321]

not saying what was right or wrong andy just the op suggestion

 

[Lee321]

But if you have a neutral to earth or live to earth fault it is going to trip everything off.

as above

 

[Andy™]

But if you have a neutral to earth or live to earth fault it is going to trip everything off.

but only if its on the non-30mA circuits

 

[a1spark]

batty he was going to fit a higher rated rcd to give discrim

Yep ! Although....

No so much the higher rating as the discimination would only be provided by to the Time delayed aspectof the 100ma R.C.D.

 

[batty]

[quote name='Andy

 

[PC Electrics]

If one circuit on the "non protected" portion of the board were to be on an MCB and the main switch was a 100mA RCD, then in the event of an earth fault on that circuit the RCD would trip. Since the RCD is the main switch, then the whole installation is now off.

RCBOs for the "non protected" ways would be the only way to comply I believe.

 

[NozSpark]

If one circuit on the "non protected" portion of the board were to be on an MCB and the main switch was a 100mA RCD, then in the event of an earth fault on that circuit the RCD would trip. Since the RCD is the main switch, then the whole installation is now off.RCBOs for the "non protected" ways would be the only way to comply I believe.

So now the question SP or DP??????