10kw 3 Phase A/C what type of protection is required?

Chris Pearson:

I am not sure why you need additional protection for this device - no sockets involved!


As an aside, other manufacturers (e.g. Eaton, Schneider) do make 4-pole RCBOs; Eaton's occupy 4 x 18 mm ways.

My NICEIC electrician suggested that it is required to have RCD protection since the AC has an outdoor unit that sits on a concrete slab slightly above soil level (he didn't use these exact words but suggested RCD protection is required for all circuits under 18th edition?).


Can someone give me a reference to the regulation that shows RCD protection would not be required?

Is there an exception for fixed installations that shows an MCB might be sufficient?


Hager apparently do this Add on block but holy moley is it expensive, want to avoid unless required - BD163T - https://hager.com/uk/products/h/bd163t-add-on-block-3p-63a-30ma-a-1mod-el

mapj1:

Presumably the RCBOs are all single phase with  neutral tail. If you need RCD protection for a load with a neutral connection, you will need a 4 pole sensing device and that will not fit a 1,2,3 bus bar.

Not sure this is entirely correct, apologies if I have misunderstood your comment.

As per my other comment post on this there seems to be devices out there that can take up an empty space and still work?

FaeLLe:

Can someone give me a reference to the regulation that shows RCD protection would not be required?


Is there an exception for fixed installations that shows an MCB might be sufficient?


Hager apparently do this Add on block but holy moley is it expensive, want to avoid unless required - BD163T - https://hager.com/uk/products/h/bd163t-add-on-block-3p-63a-30ma-a-1mod-el

BS 7671 generally states what is required rather than what is not required. See 411.3.3 for sockets and mobile equipment for use outdoors.


IIRC, the list price for Eaton's TPN RCBOs is about £500.

FaeLLe:

mapj1:

Presumably the RCBOs are all single phase with  neutral tail. If you need RCD protection for a load with a neutral connection, you will need a 4 pole sensing device and that will not fit a 1,2,3 bus bar.

Not sure this is entirely correct, apologies if I have misunderstood your comment.

As per my other comment post on this there seems to be devices out there that can take up an empty space and still work?

I may have the wrong picture. you said the board is full of RCBOs - I was trying to ask how the neutral to them is organised.

Also most 3 phase bus bar, and I am not familiar with this one, have tags that go L1 L2 L3 L1 L2 L3 , not

L1 L2 L3  N L1 L2 L3  N. A repeat pattern of 4, rather than 3.

An RCD or RCBO for a load with a neutral connetion, err, needs a neutral connection. 4 pole bus bar does exist but is not common.

The bus bar line up  is all I was asking about. It is sometimes seen that the end tag of the bus bar is removed to allow a flying N tail, but it is not really a nice fix and needs to be done carefully and well insulated, or ideally avoided.

mapj1:

FaeLLe:

mapj1:

Presumably the RCBOs are all single phase with  neutral tail. If you need RCD protection for a load with a neutral connection, you will need a 4 pole sensing device and that will not fit a 1,2,3 bus bar.

Not sure this is entirely correct, apologies if I have misunderstood your comment.

As per my other comment post on this there seems to be devices out there that can take up an empty space and still work?

I may have the wrong picture. you said the board is full of RCBOs - I was trying to ask how the neutral to them is organised.

Also most 3 phase bus bar, and I am not familiar with this one, have tags that go L1 L2 L3 L1 L2 L3 , not

L1 L2 L3  N L1 L2 L3  N. A repeat pattern of 4, rather than 3.

An RCD or RCBO for a load with a neutral connetion, err, needs a neutral connection. 4 pole bus bar does exist but is not common.

The bus bar line up  is all I was asking about. It is sometimes seen that the end tag of the bus bar is removed to allow a flying N tail, but it is not really a nice fix and needs to be done carefully and well insulated, or ideally avoided.

The Hager Invicta 3 has a seperate neutral and earth bar that lets you have a Neutral for each circuit (including a single phase circuit); so you can have a seperate N from the Neutral bar for each L1, L2, L3.

Plus Hager is all Made in France including the RCBO's, big fan of them !

mapj1:

I may have the wrong picture. you said the board is full of RCBOs - I was trying to ask how the neutral to them is organised.

Also most 3 phase bus bar, and I am not familiar with this one, have tags that go L1 L2 L3 L1 L2 L3 , not

L1 L2 L3  N L1 L2 L3  N. A repeat pattern of 4, rather than 3.

The Memshield arrangement is L1 L2 L3 N (covering L1) L2 L3 L1, etc. AFAIK, there is no reason why you should not put 3 of these RCBOs on each side of an 8 way board. Alternatively, you fill the gaps with SP devices or blanks.