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.

 

[suffolkspark]

The MCG one appears to be time delayed type AC, hager seems to be non time delayed type A

I'd want to fit a time delayed type A really, but you also need to be sure the down stream boards have non time delayed rcds upfront, or rcbos with switched neutral

 

[Raptor0014]

The MCG one appears to be time delayed type AC, hager seems to be non time delayed type A

I'd want to fit a time delayed type A really, but you also need to be sure the down stream boards have non time delayed rcds upfront, or rcbos with switched neutral

Good spot on the non-time delay. Never noticed that at first after I got sidetracked at the price.

The downstream boards are 2 x Hager split load dual 30mA RCD

The third board is a fuse box RCBO board

 

[loz2754]

Hager split loaf

Is that like Hovis 50/50?

 

[suffolkspark]

Good spot on the non-time delay. Never noticed that at first after I got sidetracked at the price.

The downstream boards are 2 x Hager split loaf dual 30mA RCD

The third board is a fuse box RCBO board

Ok, so you need to make sure those fusebox rcbos are switched neutral, if not, in the event of a N-E fault the neutral will still remain in circuit after the rcbo has tripped, likely taking out the big boy upfront

 

[Raptor0014]

Ok, so you need to make sure those fusebox rcbos are switched neutral, if not, in the event of a N-E fault the neutral will still remain in circuit after the rcbo has tripped, likely taking out the big boy upfront

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

 

[Raptor0014]

Is that like Hovis 50/50?

Yeah, but toasted

 

[suffolkspark]

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

The miniature ones are AFAIK, don't know about the full height ones though.

 

[Raptor0014]

The miniature ones are AFAIK, don't know about the full height ones though.

The full height are too.

 

[loz2754]

The full height are too.View attachment 94649

That one isn't

 

[suffolkspark]

The full height are too.View attachment 94649

That isn't, also you need to get upfront rcd of appropriate brand to match the 3phase db.

 

[loz2754]

That isn't, also you need to get upfront rcd of appropriate brand to match the 3phase db.

Unless it's to be installed in a separate enclosure of course.

 

[Raptor0014]

That one isn't

Just realised I grabbed the wrong one. I thought I had some large DP ones left. But it seems I only have the mini ones and this SP one.

 

[Raptor0014]

Unless it's to be installed in a separate enclosure of course.

Yep it will go into a enclosure.

There is no 3ph board. There is a 3ph supply and then each of the phases supplies a SP DB

 

[suffolkspark]

Yep it will go into a enclosure.

There is no 3ph board. There is a 3ph supply and then each of the phases supplies a SP DB

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

 

[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