Practicing a Consumer Unit install

[EFLImpudence]

I just thought that's what it was called because that's what people call it.

 

[JohnW2]

I just thought that's what it was called because that's what people call it.

That's precisely what I am suggesting.

However, as Sunray pointed out, I think it 'gets worse' than that, in that (as we've seen in this thread) at least some people seem to describe cables joining devices within a CU as "tri-rated" even though it's actually very unlikley that they are!

Kind Regards, John

 

[333rocky333]

I maybe wrongly assumed it was Tri rated, mainly due to the the feel and the shine of the insulation, very similar to the smaller Tri rated stuff we buy for shop internal lighting wiring, also I thought the higher temperature limit and its flame retardency, plus i recall it has higher current ratings, would all be a bonus, also never seen any fine stranded flex other than Tri rated stuff.
Rexel sell the kits, so will see if can get more info

 

[plugwash]

Trirated wire should have the details, including both the metric and american sizes should be marked on the wire, not sure if the legths in a CU are long enough for the markings to be reliably visible though.

 

[JohnW2]

I maybe wrongly assumed it was Tri rated, mainly due to the the feel and the shine of the insulation, very similar to the smaller Tri rated stuff we buy for shop internal lighting wiring, also I thought the higher temperature limit and its flame retardency, plus i recall it has higher current ratings, would all be a bonus, also never seen any fine stranded flex other than Tri rated stuff.

It would certainly be 'logical', and you may be right - but, in common with what Sunray wrote (and 'for what it's worth', given my limited experience/exposure) I haven't personally seen cables within a CU whose markings indicated (or even suggested) that it was "tri-rated".

In fact, 'larger CSA' tri-rated cables don't seem to be all that readily come by. For example, TLC appear to only do them up to 4mm². However, they do have (albeit only in 25mm²) 19-stranded 6181Y "Flexi Meter Tails" (which I presume are not 'tri-rated', since they make no such claim).

Kind Regards, John

 

[EFLImpudence]

Tri-rated has many more than 19 strands and is not sheathed so would be no good for 'tails'.

https://uk.rs-online.com/web/p/hook-up-wire/6285544

https://docs.rs-online.com/8b69/A700000007356700.pdf


I just wonder why, if the RCCB links for consumer units are not tri-rated, they bother to make them look like they are.

 

[JohnW2]

Tri-rated has many more than 19 strands and is not sheathed so would be no good for 'tails'.

I realise all that, but my point was that, although TLC don't have 'tri-rated' >4mm²,they do have those 25mm² (insulated and sheathed) 'flexible tails'

I just wonder why, if the RCCB links for consumer units are not tri-rated, they bother to make them look like they are.

In what sense are you suggesting that they do?

Kind Regards, John

 

[SUNRAY]

Wow, what a discussion.
As I said the forms supplied with BG CU's are prejointed regardless of colour/designation, either in a crimped ferrule or welded.

The standards for tri-rated cable are BS6231 UL 1015 and CSA C222 I THINK, assuming UK, US & Canada in order. I should double check But I believe it is 600/1000V rated.

In my experience the wiring supplied in CU looks and feels nothing like TR. TR is fine stranded but the insulation is not that flexible whereas that supplied in CU's is usually soft and flexible.

25mm² has lots of strands, I estimate circa 150+.

I believe double insulated does not appear in the standards for TR but I certainly haven't read the BS to that extent, but I'll not put that forward as a fact.

All proper wholesalers will supply TR cables up to the maximum of 240mm². Actually to be pedantic anything over a certain size (I believe 120mm² & above) is called Bi-rated but I've never looked at the difference between the standards.

I maybe wrongly assumed it was Tri rated, mainly due to the the feel and the shine of the insulation, very similar to the smaller Tri rated stuff we buy for shop internal lighting wiring, also I thought the higher temperature limit and its flame retardency, plus i recall it has higher current ratings, would all be a bonus, also never seen any fine stranded flex other than Tri rated stuff.
Rexel sell the kits, so will see if can get more info

TR is not suitable for use in building wiring, to the point it usually has someting like 'Not for use in conduit or raceways' printed on each reel. It is only designed for use in switchgear/appliances/control panels etc.
We got the job in a M&S food hall to stripout all of the incorrectly installed TR and replace with LSF singles and the original installer paid the bill (via the court). IIRC 1mm² on 16A lighting circuits & 2.5mm² on 25A 3ph motor circuits in bundles of maybe 50 conductors in trunking above the cold section on the retail floor. The warm trunking was found by the refridgeration guys while using an Iphone as a heat camera while checking their lagging.

Higher current rating is a myth... check the stated rating (example 6mm² TR and T&E 53A - again from memory) AND the derating factors and you'll soon see how quickly that maximum current falls than T&E.

Are you telling us you have never seen 3 core flex and its fine strands?

 

[Jupiter01]

UPDATE: I wanted to share my progress with this first Consumer Unit install (Photos attached). I've got a few more breakers to wire up. Thanks for all the advice and I would welcome your constructive feedback.


I have a few specific questions please:

• The Neutral terminals are numbered from 1-5 and I can clearly see that there is room for 5 Breakers next to each RCD. Hence, it's clear which cable goes where.
  The Earth terminals don't follow the same numbering scheme and this is causing me some confusion. They range from 1-13 and it's unclear on which breaker goes where
  
  
  
  
• I was struggling with the length of cables and how much I should retain. I tucked the excess cable in the corner of the CU but was unsure on whether this is the right thing to do.
• Finally, should the wire for N and E poke out of the top of the terminal as shown in the above image?

Thanks again.

 

[Jupiter01]

Can I get your view on the above questions please. I’ve not wired in the remaining MCB’s until I have this clarification.
Thanks for your support.

 

[EFLImpudence]

The Neutral terminals are numbered from 1-5 and I can clearly see that there is room for 5 Breakers next to each RCD. Hence, it's clear which cable goes where.The Earth terminals don't follow the same numbering scheme and this is causing me some confusion. They range from 1-13 and it's unclear on which breaker goes where

You can buy new stickers or just make your own and number them however you want.

I was struggling with the length of cables and how much I should retain. I tucked the excess cable in the corner of the CU but was unsure on whether this is the right thing to do.

Well, there is no 'right' - just tidiness by cutting the wires to appropriate lengths. You get used to it.

I think it turns out better (like junction boxes and ceiling rose) if you connect all the CPS first, tuck out of the way, then the neutrals then the lines.

Finally, should the wire for N and E poke out of the top of the terminal as shown in the above image?

Not sure it matters as long as there isn't miles of bare cable beneath.

 

[JohnW2]

Can I get your view on the above questions please. I’ve not wired in the remaining MCB’s until I have this clarification. Thanks for your support.

Since you're anxious for responses, for starters, and for what it's worth, these asre the thoughts of a non-electrician ...

The Neutral terminals are numbered from 1-5 and I can clearly see that there is room for 5 Breakers next to each RCD. Hence, it's clear which cable goes where. ... The Earth terminals don't follow the same numbering scheme and this is causing me some confusion. They range from 1-13 and it's unclear on which breaker goes where ...

I would just (probably just 'mentally') count/number all of the devices which supply circuits (i.e. MCBs/RCBOs, not RCDs or Main Switch) from left to right, and then use the corresponding earth bar terminals with the corresponding numbers.

... I was struggling with the length of cables and how much I should retain. I tucked the excess cable in the corner of the CU but was unsure on whether this is the right thing to do.

The neatest solution is to use the minimum length possible, and some professionals take pride in the neatness that results in, but that can become a nuisance if/when one subsequently wants to change anything. I personally therefore tend to be very generous in how much 'slack' I leave, which means that my CUs end up looking anything but neat. Somewhere there is probably a sensible middle-ground compromise, and I don't think there is any 'right or wrong'.

... Finally, should the wire for N and E poke out of the top of the terminal as shown in the above image?

Others will probably disagree, but I personally like the 'reassurance' of seeing a little of the conductor 'poking through'. I can't see any downside of doing that for the earth bar in any sort of CU, but I'd be a bit more hesitant to do it with the neutrals in a metal CU. I suspect views about this will vary.

Hope that may give a little help.

Kind Regards, John

 

[333rocky333]

The brown in Mcb 1 looks like it has a tight loop in it, that should be avoided and your technique for stripping the sheath in the sockets needs slight improvement.
The cables will protrude through the earth terminals, that is good as you can see there in, its likely plastic above and not an issue and better than exposed copper on show beneath in my opinion

 

[EFLImpudence]

You don't want to end up like this.

 

[Jupiter01]

Not sure it matters as long as there isn't miles of bare cable beneath

No more than what you get with the default cables - that are already wired in!