Which conductor colours to use?

[BrianHJR]

If sleeving conductors at both ends, does it really matter which underlying conductor colour is being used for what?

Background is that I’m installing an electric boiler into a commercial building for a charity. The boiler is single phase, 12KW, 63 amps rated with 10mm conductors specified.
The DB is 3 phase.
The new installation will be professionally tested by a qualified professional as soon as possible after installation.

Due to having been donated a roll of 3x16mm SWA, that’s what I’m using from the 63 amp MCB in the DB to a rotary switch coupled to the boiler, with 10mm singles from switch into boiler terminals (because 16mm will not fit the screw terminals).

The 3-core is in new tri-phase colours. Therefore I’m questioning which I should best use for this single phase supply.

As I understand it’s preferred to dissociate the black colour from the old use as a neutral, I’d had that set aside as the earth conductor and sleeved accordingly.
That leaves me with grey and brown for phase and neutral.
Boiler is going to be running off the grey phase, but I understand the live will need to be sleeved in brown anyway? So what is likely to cause the least confusion?
Grey sleeved in brown as phase, and brown sleeved in blue as neutral?
or brown unsleeved as phase and grey sleeved blue as neutral? This is certainly simpler.

Am I just overthinking all this as the sleeving makes the original colours irrelevant anyway?
?
Thanks in advance...

 

[westward10]

It doesn't really matter providing they are correctly identified. A single phase line conductor should be brown so it makes sense to utilise the brown. Most people use the grey as neutral and black as cpc but as already stated it doesn't matter providing they are correctly identified. Have you ever made off a 16.0 swa before especially at a rotary switch, that will not be easy.

 

[littlespark]

Brown for live, grey sleeved in blue for neutral. Black sleeved in g/y for cpc.

further upstream, there isn’t a “grey” phase... its L3.

 

[BrianHJR]

Thanks for the confirmation.
I did some 25mm on the main installation - it’s getting more like plumbing than wiring at that size...
16 doesn’t seem too bad in comparison. But yes although tight, it’s a big TPN switch so there is room to manoeuvre...

 

[BrianHJR]

further upstream, there isn’t a “grey” phase... its L3.

Yes of course - makes perfect sense when I think about it properly!

Again, thanks to both of you for the reassurance that I’m on the right track.

 

[BrianHJR]

A further question; the installation manual stipulates heat resistant cable for the final connection into the top of the boiler where the main power connects into terminals on a circuit board, very close to the exiting copper flow pipe.

I can procure 10mm heat resistant flex, albeit at exorbitant cost to the charity for a single meter (we only need less than a foot)!

The terminals inside the boiler appear suitable for this specification of stranded type cable, but those inside the rotary switch will likely not - will I need 10mm ferrules?

If I use standard PVC cable singles could it be fitted with a heat resistant over-sheathing instead?

Thanks again. I work full time and volunteer my occasional spare days to do this work for the charity, so I have to try to use time and resources as efficiently as possible...
?

 

[westward10]

If they are not clamp type terminals then yes you should fit ferrules for flexible cable.

 

[BrianHJR]

If they are not clamp type terminals then yes you should fit ferrules for flexible cable.

[Googles 10mm ferrules]
I’ve got a kit of bootlace type kit and a square crimper, but nowhere near the requisite size for this.
?

 

[westward10]

You can ask the electrician who is signing it off if they have the tools and parts otherwise you are stuck unless you purchase the tool.

 

[BrianHJR]

You can ask the electrician who is signing it off if they have the tools and parts otherwise you are stuck unless you purchase the tool.

I can’t guarantee their availability and we can’t afford too much of their time, so I’d prefer to get it sorted ASAP and then just have them turn up with it ready to go.
I’m leaning towards standard singles and heat resistant sleeving as that’s looking like the lowest cost and quickest option...

 

[westward10]

If the instructions recommend heat resistant cable then that is what you should use.

 

[BrianHJR]

The manual also states that the installation should be done in accordance with the relevant regulations.
Does anyone have sight of the part of them that covers heat resistance?
I would be inclined to put forward the hypothesis that standard cable becomes heat resistant cable when appropriately sleeved, but I’d be interested in any other opinion.

 

[westward10]

Relevant Regulations could cover a multitude of different things which is why it is a minefield for someone who isn't suitably equipped/competent to do this sort of thing. Charity or not it is always advisable to seek a professional to carry out these works.

 

[BrianHJR]

Relevant Regulations could cover a multitude of different things which is why it is a minefield for someone who isn't suitably equipped/competent to do this sort of thing. Charity or not it is always advisable to seek a professional to carry out these works.

Thanks for your concern.
That’s not going to happen, although as I say the installation is being completed to a sufficiently high standard to ensure that it can be tested and inspected as safe, by a suitably qualified person.

 

[DPG]

Thanks for your concern.
That’s not going to happen, although as I say the installation is being completed to a sufficiently high standard to ensure that it can be tested and inspected as safe, by a suitably qualified person.

You will need to ask whoever is testing and certifying it if they are willing to put their name to normal pvc cable with heatproof sleeving.

 

[Lucien Nunes]

If there is a circuit board inside the box it's unlikely to be getting particularly hot, although the heat developed in the connection resistance and the normal dissipation of the cable will raise the temperature of an already warm cable. Heat-resistant sleeving will not stop the original insulation deteriorating at high temperature. What can ultimately happen in extreme cases is that the insulation hardens and cracks, leaving the conductor insulated only with the sleeving. The question then is whether that is an adequate replacement for the insulation.