How many metres of electrica cable will i need approximately

[ban-all-sheds]

Who knows?! (I refer you to our previous discussions about that question!). Given that the Table distinguishes between "Lighting", "Power" and "Signalling and Control" circuits, it clearly wasn't the intention of whoever wrote it that one should use the "what it can only mean" definition of yours above.

What their intention was is one thing.

What they ended up putting in the regulations is another, apparently different, thing.

 

[JohnW2]

So what do you reckon that a 'control' circuit is, then?

Difficult to say really. Wiring that does not directly switch 240v loads perhaps.

That would make no sense. The Table clearly applies to LV, and there is no point in having a circuit, cable or conductor if there is no 'load', even if it's only the coil of a relay or contactor!

Kind Regards, John

 

[JohnW2]

Who knows?! (I refer you to our previous discussions about that question!). Given that the Table distinguishes between "Lighting", "Power" and "Signalling and Control" circuits, it clearly wasn't the intention of whoever wrote it that one should use the "what it can only mean" definition of yours above.

What their intention was is one thing. What they ended up putting in the regulations is another, apparently different, thing.

So are you saying that 1.0mm² cable is not acceptable for lighting circuits, since they fulfil your definition of a 'power circuit', the minimum CSA for which is 1.5mm²?

IMO, in relation to both lighting and CH control applications, this issue just requires a little bit of basic common sense!

Kind Regards, John

 

[ban-all-sheds]

So are you saying that 1.0mm² cable is not acceptable for lighting circuits, since they fulfil your definition of a 'power circuit', the minimum CSA for which is 1.5mm²?

It's simple.

Either Table 54.1 says that you can use 1mm² for lighting circuits which do not use power, or it says that you have to use 1.5mm² for circuits with an undefined attribute, or it is total nonsense and therefore must be ignored otherwise it becomes impossible to have electric lighting and comply with BS 7671.

I vote for the latter.

 

[JohnW2]

It's simple. ... Either Table 54.1 says that you can use 1mm² for lighting circuits which do not use power, or it says that you have to use 1.5mm² for circuits with an undefined attribute, or it is total nonsense and therefore must be ignored otherwise it becomes impossible to have electric lighting and comply with BS 7671. ... I vote for the latter.

IMO, in relation to both lighting and CH control applications, this issue just requires a little bit of basic common sense.

Kind Regards, John

 

[ban-all-sheds]

And the same common sense says that you can use 1.0mm² for non-lighting circuits if you want and if the normal rules for cable/MCB size are followed.

 

[securespark]

I concur with John.

7671 makes a distinction between power circuits and lighting circuits.

As previously mentioned, there is a distinction between those circuits and signalling and control circuits.

Room, frost, cyl stats, progs, etc... can all be wired in 0.5 upwards.

To my mind, so can boilers and pumps. All gas CH equipment is fused down to 3A anyhow. And some boilers and pumps I have seen have come prewired with 0.5 or 0.75 flexes, so even if you adhered to the 1.5 rule, the circuit would still contain conducts with a smaller csa.

If you really want to split hairs, you could argue that a boiler contains signalling or control equipment and a pump is an item of control equipment, so are exempt from the 1.5 rule anyway.

 

[ban-all-sheds]

7671 makes a distinction between power circuits and lighting circuits.

It might think it does.

But as it does not define the former, and as the latter also take power to lights, what it actually does is to contain something utterly impossible to comply with because it is nonsense.

So you have to ignore it.