3Ph sub-mains supplied via 5-core NYY, not SWA. OK or not?

Good morning
I need to fit a new 3 phase dis board in an annexe I'm building at my own house.
Usually I'd use SWA, or singles in conduit/trunking, but as the run is all in loft space and not liable to physical damage (no rodents), I'm thinking of using surface-clipped 5-core 16mm NYY instead, especially as there are some tight-ish turns, and space in the board it's coming from is also tight.
I can think of no technical reason why this is not OK. Possibly it's routine?
Any comments?
Cheers
Mark

this seems to agree with you:
NYY - Protected Cables - https://www.tlc-direct.co.uk/Main_Index/Cable_Index/NYY/index.html?ad_position=%7badposition%7d&source=msn&ad_id=%7bcreative%7d&kw=www.tlc-direct.co.uk%2fMain_Index%2fCable_Index%2f&matchtype=b&ad_type=%7badtype%7d&qry=NYY-J%20cable&campaign=dynamicsearchads&msclkid=6c55c34893d2178ddf49982ca7077640

Is this new CU an addition to the existing house CU?
Why 16mm?

Spoon said:

Is this new CU an addition to the existing house CU?
Why 16mm?

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maybe it's a cannabis farm extension.

id go with nyyj aswell

Spoon said:

Is this new CU an addition to the existing house CU?
Why 16mm?

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Because NYY's not easy to find in 25mm

New self-build extension which is eventually for holiday rental (It's my retirement fund!)
Fed from the main DB which is 100A x 3 in 25mm.
There's no reason not to allow for future expansion in the annexe (ie do it once!) and I want to add a Tesla charger 3 x 16A or 3 x 32A to encourage the right kind of rental client

MarkRibbands said:

Because NYY's not easy to find in 25mm

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Eland do 5 core 25mm... Link A9N525

The only thing i would say is check if its stranded..... I got some 6mm nyyj on a job recently and it was solid core!

Would this be in Malaysia or UK?

4c 25mm HO7 and a 16mm GY would have been my first look.
NYY I think is always solid core.

Rockingit said:

4c 25mm HO7 and a 16mm GY would have been my first look.
NYY I think is always solid core.

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I was thinking h07rn as well, but why not 5 core?

rapparee said:

I was thinking h07rn as well, but why not 5 core?

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4c + G/Y is just cheaper and also if he's got some tight turns then it's more flexible /sharper radius too. Also makes it easier (smaller) to gland into a panel if space is tight.

Rockingit said:

4c + G/Y is just cheaper and also if he's got some tight turns then it's more flexible /sharper radius too. Also makes it easier (smaller) to gland into a panel if space is tight.

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Yeah, it'd take a 50mm stuffing gland for 5 core. I'm using a lot of it recently.

Midwest said:

Would this be in Malaysia or UK?

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UK

Thanks for the ideas.
BTW, I was joking about 25mm as I thought another poster was implying 16 was too big for a small annexe! It is only a 10m run, and will have a 32 or 40A TP MCB.
I hadn't considered H07RN. If as SuffolkSpark says, 16mm NYY might be solid (really?!) that's no good. I'm going to order 1m to check.
The thing is, although I know rubber flex is totally fine, both from a technical and regulation perspective, I can easily imagine a future inspecting electrician saying that some cowboy has used FLEX (!) for a sub main rather than SWA, like you 'have to'. Can anyone here say that could never happen?
At least NYY looks like SWA.

The only thing you'd need to do to HO7RN would be to put crimps on the terminations as it's fine stranded, other than that, fill yer boots man. Idiots will always walk among us, we can't see into the future except to use common sense today. Besides, I've lost count of the number of submains run in 16mm t+e through all kinds of spaces where it could be argued something else would have been better. If you're only running 32-40A then I'd suggest 10mm 5c HO7 is plenty overkill.

here's a datasheet for you......

Rockingit said:

The only thing you'd need to do to HO7RN would be to put crimps on the terminations as it's fine stranded, other than that, fill yer boots man. Idiots will always walk among us, we can't see into the future except to use common sense today. Besides, I've lost count of the number of submains run in 16mm t+e through all kinds of spaces where it could be argued something else would have been better. If you're only running 32-40A then I'd suggest 10mm 5c HO7 is plenty overkill.

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Your preaching to the converted.

I did a job in SWA last year, 35mm 5 core 160A supply, I had fitters and toolmaker conscripted in to help me pull it in.

I vowed from then, that ho7 would be my new cable of choice, I think it is actually more robust than SWA, especially in the bigger sizes.

Although the spec for 16mm NYY states 'solid core' I was right to not believe it. A sample arrived today. 16mm, at least, is definitely stranded, strips really easily, and looks easy to work with.




So I'm going to go with the NYY at £6.77/m rather than H07RN which is £10.17/m.
Many thanks for all the helpful advice.

.

Wilko said:

Hi - it would be good to confirm the conductor types as the specs I looked at seemed to say NYY was a solid conductor per core even at 16mm. ...

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Thanks Wilko, but look at my pictures immediately above.
I too read that 'solid core' spec, but didn't believe it, so ordered a 1m sample.
The specs are wrong.

FYI

Copy of email from Basec.

Thanks for your enquiry via our website.

The situation on SY CY etc. has been updated since our previous release, and there is now a tougher line being taken against the use of these cables.

There is now a specific paragraph in the On Site Guide to the IET Wiring Regulations BS 7671 Amendment 3 (the current edition), which is the practical guide registered electricians are expected to follow, and which states the following:

———

7.9 Installation and use of non-standard cables

For the purposes of this guidance publication and ensuring compliance with BS 7671, the installation and use of non-standard cables, such as SY, CY and YY cables is discouraged.
The letters signify:

S – steel braid
Y – PVC
C – copper braid

To identify:
SY cables - steel braided, usually translucent sheath, PVC insulated flexible conductors
YY cables – usually grey PVC sheath, PVC insulated flexible conductors
CY cables – tinned copper wire braid, usually grey PVC sheath, PVC insulated flexible conductors

To meet the requirements of BS 7671, every item of equipment must comply with a British or Harmonized Standard, in the absence of such, reference can be made to IEC standards or the appropriate standard of another country.

SY, YY and CY cables are not made to British or Harmonised Standards. Some manufacturers state that their cables “generally” comply with a British Standard; this is not deemed sufficient for the purposes of BS 7671.

It is important that cables have approval from an independent testing organisation and installers should ensure that all cables purchased have manufacturers’ identification and a specification reference/standard number printed on the sheath to enable testing, if necessary, and traceability.

———


SY, YY or CY cables are not made such that their construction, materials, voltage rating, temperature rating or performance claims to conform fully to any British or Harmonised standard, or indeed to international or other national standards. Different suppliers sometimes make a number of claims that the cables conform ‘generally to’ particular standards / specifications, but these are invariably unsubstantiated and in fact the cables cannot conform to various aspects of the quoted specifications. Because of the lack of specification these cables can and will be of variable construction and performance, and a purchaser / supplier should be very wary, particularly of making recommendations. We are not aware of any such cables that have independent testing or approval.

There are specific and onerous engineering assessment procedures in the Wiring Regulations where it is proposed to use non-standardised products. Most electricians would not have the knowledge to conduct such assessments or keep the appropriate records.

I also attach for your information a short guidance note published by the ECA on the topic.

The key clauses in the IET wiring regulations are 133.1.1, 133.1.3 and 511.1, 511.2.

If you require further information please contact us again. My colleague Simon Brown can deal with many installation issues.

Best regards,

Dr Jeremy Hodge
Chief Executive

cid:[email protected] +44 (0)1908 267300
cid:[email protected] +44 (0)7900 505950
cid:[email protected] +44 (0)1908 267255
cid:[email protected] [email protected]
cid:[email protected] www.basec.org.uk

It seems quite certain that from the above that the cable would not be compliant with BS7671. In which case the certificate you would be issuing should state the departure from regulations. You say it is going via a loft. I imagine that would mean it is going through insulation? In which case the CCC rating would be halved (circa). In a cold winter where the gas fired(?) heating fails and heaters are used you may well get to the top of what the installation you are proposing can safely accommodate. What route does the supply to the DB for the annexe take? Personally for the above reasons I would not use the cable you are using and would opt for SWA as being a no brainer as it does comply with BS7671 subject to the route taken and also the type of supply. i.e. is it TNS etc? In designing an installation account should be taken of future use and if it were used for say a granny annexe and cookers and electric showers were installed would the existing supply be able to meet that change of use. Of course there are many factors I do not know of related to that so this is conjecture or an educated guess on some of the downsides to what you are proposing.

Vortigern said:

It seems quite certain that from the above that the cable would not be compliant with BS7671

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NYY does comply as it is to an IEC standard which the regs do say we can use-infact the paragraph stating this is in the middle of Charlie's post above. So it does not need to go down as a departure. It is not the same as CY, YY, SY.

NYYJ is not the same as CY SY and YY, just because it uses the same letters it doesn't necessarily not comply.

You can see in this data sheet that it does comply with international and BS EN standards.