Practicing a Consumer Unit install

[JohnW2]

The incoming supply’s earth connects to the earth terminal that you circled on the picture.

Indeed. However, in the case of the OP's exercise, in which the "incoming supply's earth" will be the CPC of a modest piece of flex, it might be wiser to use one of the other positions on the earth bar, since the left-most one or two often/usually have appreciably larger 'holes' (to accommodate large conductors), such that the CPC of flex might be a bit 'lost' in one of them.

Kind Regards, John

 

[333rocky333]

They seem quite typical of many makes to me and it's only one cable and one bussbar.
Is that not the same as the pic of your CU?

I assumed theres Two brown cables, one to each RCD

 

[JohnW2]

I assumed theres Two brown cables, one to each RCD

Indeed, but that's totally normal for a 'high integrity' CU, isn't it? (how else could they do it?).

Kind Regards, John

 

[EFLImpudence]

They "could have" done it like they have done the neutrals - all the current going through one though.

 

[JohnW2]

They "could have" done it like they have done the neutrals - all the current going through one though.

They 'could have', but I don't think that they usually do, do they?

Kind Regards, John

 

[EFLImpudence]

The one in Rocky's picture is the same - for the neutrals.

There would need to be three cables in the main switch otherwise.

 

[JohnW2]

The one in Rocky's picture is the same - for the neutrals. There would need to be three cables in the main switch otherwise.

Exactly, and I presume that (avoidance of 3 cables) is probably the reason why the neutrals are usually done that way in 'high integrity' CUs. However, given that they are clearly happy with two (neutral) cables into a main switch terminal, that is presumably why they usually seem also happy to have two cables (plus the busbar) in the switch's L terminal, isn't it?

Kind Regards, John

 

[EFLImpudence]

Exactly, and I presume that (avoidance of 3 cables) is probably the reason why the neutrals are usually done that way in 'high integrity' CUs.

What is the alternative if three of those tri-rated cables won't go in the terminal?
Some CUs (used to) come with a solid rod, which is a lot thinner, (can't remember which) shaped for the main switch to HI neutral terminal - and some t-r cables have pin-ferrules fitted.

Having said that, if one of the t-r cables is capable of carrying the total load of the RCCB circuits, then three smaller cables could be used.

However, given that they are clearly happy with two (neutral) cables into a main switch terminal, that is presumably why they usually seem also happy to have two cables (plus the busbar) in the switch's L terminal, isn't it?

Again, little choice but one flat bus-bar tooth isn't going to add much.

 

[JohnW2]

What is the alternative if three of those tri-rated cables won't go in the terminal?

Obviously no alternative if that is the case - which, as I said, is probably why they do the neutrals ('looping' them) as they do, but ...

Again, little choice but one flat bus-bar tooth isn't going to add much.

Exactly my point. If two neutral cables will fit in the N terminal of the switch, then it's very likely that two L cables plus the busbar will fit into the N terminal of the switch - so, in the case of the L's, no need to use the 'looping' method they use for the neutrals.

Kind Regards, John

 

[SUNRAY]

The BG boxes do supply their cables ready to install (or even pre installed, it varies) with the 2 wires already joined together - either welded or crimped. Therefore there is only one item to terminate with the bussbar and the ends to go into the neutral bars suitably prepared with a ferule or lug. Unlike the pictured Wylex who don't care about the thin strands getting butchered by the terminal screws.


Additionally I have not yet been aware of finding Tri-rated wire in any CU, It's just flex in my experience. Not saying never, just not seen yet.

 

[JohnW2]

The BG boxes do supply their cables ready to install (or even pre installed, it varies) with the 2 wires already joined together - either welded or crimped. Therefore there is only one item to terminate with the bussbar and the ends to go into the neutral bars suitably prepared with a ferule or lug.

Are you talking just about the neutrals (for which what you describe seems to be common) or also the L's (for which, at least in my experience, two cables into the switch {one for each RCD}, together with the busbar seems very common)?

Additionally I have not yet been aware of finding Tri-rated wire in any CU, It's just flex in my experience. Not saying never, just not seen yet.

Yes, I've been wondering about that, particularly since I have, to the best of my knowledge, never handled, let alone used, something explicitly described as "tri-rated" cable. I may be wrong, but I have a suspicion that some people use that term to refer to any cables they find within a CU or similar situation - even though, as you say, it probably rarely will be correct (at least, for CUs).

I also find the term "tri-rated" to be rather odd. The words, per se, seem to merely indicate that it satisfies Standards in three territories - Canada, US and Europe, but do not, per se, give any indication of what those three sets of Standards 'rate' it for, nor what it is intended to be used for. Another of those odd bits of electrical industry terminology, I guess!

Kind Regards, John

 

[SUNRAY]

Are you talking just about the neutrals (for which what you describe seems to be common) or also the L's (for which, at least in my experience, two cables into the switch {one for each RCD}, together with the busbar seems very common)?
Yes, I've been wondering about that, particularly since I have, to the best of my knowledge, never handled, let alone used, something explicitly described as "tri-rated" cable. I may be wrong, but I have a suspicion that some people use that term to refer to any cables they find within a CU or similar situation - even though, as you say, it probably rarely will be correct (at least, for CUs).

The wires are supplied ready to install and any where 2 wires go to a terminal are pre jointed - regardless of colour.

I also find the term "tri-rated" to be rather odd. The words, per se, seem to merely indicate that it satisfies Standards in three territories - Canada, US and Europe, but do not, per se, give any indication of what those three sets of Standards 'rate' it for, nor what it is intended to be used for. Another of those odd bits of electrical industry terminology, I guess!

Kind Regards, John

You are correct, the 3 specs are basically similar hence why all TR wire is marked in AWG and metric sizes.

 

[JohnW2]

The wires are supplied ready to install and any where 2 wires go to a terminal are pre jointed - regardless of colour.

Yes, but you're somewhat evading the question Do the brown ones come 'pre-joined', so that only one (end) has to go into the main switch, or not?

You are correct, the 3 specs are basically similar hence why all TR wire is marked in AWG and metric sizes.

Sure, but, as I said, the term "Tri-rated", per se, gives no indication of what the three similar standards 'rate it' for. For all one knows (from "tri-rated"), they might all be 'rated' for use with 'voltages up to 50V'!

It's a bit like the "COP" climate change conferences. I was amazed when I first discovered that "COP" is an abbreviation for "Conference Of the Parties" - which tells one as little as (maybe even less than) "Tri-Rated"

Kind Regards, John

 

[plugwash]

My understanding is that "tri-rated" wire was developed/intended to be used for internal wiring inside equipment such that said equipment can be sold on both sides of the pond. Afaict it is always fine stranded, I suspect because the specifications for fine stranded wire allow a greater leeway in terms of the physical size of the wire allowing the manufacturer to meet the standards for both a European size and a north-American size*.

AIUI in the US it is specifically rated only as "appliance wiring material", i.e. for use inside equipment not for use in building wiring. I don't know what exactly it is approved for in Europe.

* At least in Europe while we reffer to cables by the nominal "cross-sectional area" of copper, what the standards actually specify is a maximum overall diameter and a maximum resistance, the maximum diameter is larger for fine stranded wire than for stranded wire and larger for stranded wire than for solid wire.

 

[JohnW2]

My understanding is that "tri-rated" wire was developed/intended to be used for internal wiring inside equipment such that said equipment can be sold on both sides of the pond. Afaict it is always fine stranded, I suspect because the specifications for fine stranded wire allow a greater leeway in terms of the physical size of the wire allowing the manufacturer to meet the standards for both a European size and a north-American size*.

Yes, my understanding is exactly the same as that.

However, as I presume you understand, my point was that describing them as "tri-rated" conveys none of that, and could mean virtually anything (like that they were only 'rated' for ELV, albeit in multiple countries)!

Kind Regards, John