Correct Type-S Upfront RCD for 3Ph TT System

[Raptor0014]

Hi all,

Doing an EICR on a property which is 3Ph in and then 3 x Single phase boards from that. However it's on a TT System and doesn't have a upfront 100mA RCD and I am not aware of any reason why one wouldn't be required.

So I am just wondering if this MCG one will suffice into an enclosure.

4 Pole Time Delay Rc Ds | Switchgear & Distribution | CEF

Or if I need to go balls to the wall and get this Hager one

100A 4 Pole 100mA Type A RCD

All RCDs have trip free mechanisms and can be padlocked either On or Off

www.cef.co.uk

Obviously I need to justify to the client the cost difference and brand name I know Hager is great kit. But if anyone has any other recommendations it would be appreciated.

 

[Raptor0014]

Oh sorry I misunderstood... so 3 phase head into what... 3x single phase switch fuses? Then off to each single phase board....

From this

Into the basic 100a 3pole Isolator

then from there round tothe 2 boards below the head and the third board has a fused switch at 60A

 

[Raptor0014]

I am right is thinking it has to be a time delayed RCD upfront and not just a 100mA or 300mA?

 

[suffolkspark]

I am right is thinking it has to be a time delayed RCD upfront and not just a 100mA or 300mA?

Yes it would need to be time delayed... but looking at that, if both hager boards out of shot below the head are plastic, I'd just swap out that switch fuse for a new one and fit a 2pole 100ma type S / type A in there as that things got basic insulation hanging out it's arse anyway.

 

[Raptor0014]

Yes it would need to be time delayed... but looking at that, if both hager boards out of shot below the head are plastic, I'd just swap out that switch fuse for a new one and fit a 2pole 100ma type S / type A in there as that things got basic insulation hanging out it's arse anyway.

I've got that and a lot lot more coded on the EICR

I thought the tails needed to be protected regardless if the CU was plastic (they are)? Hence going to swap out the basic isolator and make that a 3P 100a 100mA time delayed RCD?

Or have I got that wrong?

 

[Raptor0014]

So I will use something like this (found a type A time delay) which I will put in a separate enclosure to replace that 100A isolator.

100A 4 Pole 100mA Type A Time Delay RCD

Test button

www.cef.co.uk

 

[Risteard]

All fusebox RCBOs are now switched neutral. I don't think they make any other kind now.

Only the compact ones.

 

[suffolkspark]

So I will use something like this (found a type A time delay) which I will put in a separate enclosure to replace that 100A isolator.

100A 4 Pole 100mA Type A Time Delay RCD

Test button

www.cef.co.uk

If those fusebox rcbos aren't switched neutral your gonna have a problem....

The tails appear to all be visible there so I wouldn't add upfront rcd protection to anything other than the submain going off to the kitchen.

 

[westward10]

If the supply conductors enter an all insulated enclosure then fault protection is not required.

 

[Raptor0014]

If those fusebox rcbos aren't switched neutral your gonna have a problem....

The tails appear to all be visible there so I wouldn't add upfront rcd protection to anything other than the submain going off to the kitchen.

They are definitely DP as they're the mini ones.

I'm a little confused as to why you say a upfront for the whole system isn't required? I was led to believe when I did my course (granted I think 'guru graham' as I used to call him was good at passing off his thoughts as a regulation sometimes) that on a TT it must have upfront RCD to protect the tails regardless.

I need to make sure this one has no hiccups as it will be looked at by my CPS assessor so that I can pay for the privilege of being a member for another year....

So I am not questioning your judgement. I just need to know how that fits into the regs as my understanding is its a no ifs, buts or maybes. But could be the way I've had it explained.

 

[westward10]

Why do you think they need rcd protection.

 

[Raptor0014]

The way I had it explained was that if a fault occurred between the tails and the board then it wouldn't be picked up by the RCD's in the board.

 

[westward10]

What type of fault.

 

[nicebutdim]

The full height are

Just did so quick research and can find nothing to suggest Fusebox have made full height RCBOs that switch both poles. Their new AFDD RCBOs are tall and switch both poles.

 

[Raptor0014]

What type of fault.

Line to earth

 

[Raptor0014]

Just did so quick research and can find nothing to suggest Fusebox have made full height RCBOs that switch both poles. Their new AFDD RCBOs are tall and switch both poles.

Yeah I think I have gotten it confused with the mini ones and the AFDD ones I was quoting for the other day (some bloke wanted all 14 circuits protected with AFDD! Soon changed his mind when I told him that was £1750 before we even started on the remaining materials and labour etc)