524.1 & table 52.3.


or a lighting circuit?

But wire it in flex and 0.75 is OK. Where's the logic in all this? I can only imagine that there's a move to harmonise us with the continent where 1.5 is the minimum in general, but anticipating an outcry, the usual committee compromise response was to have an exemption for lighting circuits for the moment.

Is CH wiring - control wiring (as it connects the thermostat) or power wiring (as it powers the pump)?

- Andy.

I agree that a lighting circuit is still a lighting circuit even if some other small load is connected.
However pedantic inspectors do not share this view, and some at least state that 1.0mm is only for lighting circuits, and that the connection of anything other other than a light renders the circuit a power circuit.

This whole lighting/power thing is getting silly now...

We can plug a table lamp into a socket on a 32A ring - so should we apply lighting (3%) v.d. calculations to ensure proper functioning of incandescent lamps?

- Andy.

I just knew I was getting too old for this lark.
The 15th edition issued in the 1980's was a sea-change from the old wiring regulations. Up till that time, you did what the book said and then it complied.
The 'harmonisation' from the 15th was intended to allow the designer (installer) to design a suitable electrical installation that was safe and met the requirements of the client. Look at it as an upgrade in your knowledge skill.

What happened? You all seem to be like lemmings and not thinking for yourselves.
Buy a book, go on a course, common denomination, one size fits all!

Bring back the 14th and you will all be happy with no arguments.

Must get out more.Must get out more.Must get out more.........................................................

-------------------------
Norman

Oh, how much I agree with you!

Some of the assertions made on this forum as to what complies or not are simply absurd and have no basis whatever.

"Nevertheles, regulations now require at least 1.5mm for power circuits"

What Regulation is that?

524.1 & table 52.3.

Thanks, I`d missed that one.

-------------------------
Regards,
Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik

Next question - does 524.1 & table 52.3 apply to just live conductors? - or c.p.c.s too?

(runs for bunker)

- Andy.

Take a look at Chapter 53 - 520.1 - the regulation group under which Table 52.3 falls ?

So to answer the question, it does apply to CPC's although we are allowed to varyCPC cross sectional area by virtue of Chapter 54 and specifically by 543.

In 543, we have a simple method that sizes the CPC to match the line conductors, but not neccessarily a live conductor - so it could be argued that in a 1.5mm2 "power" circuit, a 1.5mm2 CPC is required unless the designer wishes to calculate - which is, of course, what happens when any designer selects T&E as an installation cable type

Regards

OMS

-------------------------
Failure is always an option

Even if we calculate a c.p.c. size in accordance with chapter 543.1.3 (or a live conductor according to 434.5.2), doesn't the minimum of 52.3 still apply?

So if we stick with T&E I'd need a minimum of 2.5mm2? That'll be fun on the smoke detector circuit and the bell transformer on its own MCB.

Like I say, the regs are getting a bit silly on this one now.

- Andy.

I would say it doesn't Andy - Chaper 52 being overidden specifically for CPC CSA by Chapter 54.

At least that's how I've aways read it - ie Chapter 52 applies to Live, Line and CPC's except that other sections (specifically Chapter 54) in this case has the allowable variation (in in many cases, actually mandates far larger minimum sizes for protective conductors).

I suppose a consideration of the term "circuit" as she is writ, would clarify the intent as well - ie does a circuit also contain a CPC - it need not obviously.

There's always one

Regards

OMS

-------------------------
Failure is always an option

Humm. The note to 520.1 seems to say 54 contains further requirements - not alternative/replacement ones.

Would you be happy with a 1.5mm2 aluminium c.p.c. on the basis that it satisfied the adiabatic and so overrode table 52.3 ? - it's the same table that prohibits <16mm2 Al, as is asking for 1.5mm Cu - so same logic should apply presumably?


While I agree that there need not always be a c.p.c. (a circuit feeding double-insulated equipment in an installation under supervision for example), but that's not the same as whether a c.p.c. is part of the circuit if it is present. (Likewise we don't always distribute N, but that doesn't stop N being a circuit conductor).

Given, in an ADS system at least, the c.p.c. is sized to match the protective device - it's protection from fault (overcurrent) is shared with the live conductors, so seems to meet the definition.

- Andy.

(edited to fix typo in reg no)

Regards

OMS

-------------------------
Failure is always an option

I'm not sure about "changing" the size - just two different methods of deciding what the c.p.c. size should be (one related to the live conductors, the other related to the protective device) - if one method is subject to the minima of table 52.3 the I don't see anything that suggested that the other method should be treated differently.


I'd infer that BS 7671 just doesn't have an opinion about minimum size when it comes to other materials. I guess copper-clad steel could be used as live conductors, but that wouldn't imply that table 52.3 doesn't apply to live conductors.

- Andy.

Regards

OMS

-------------------------
Failure is always an option

That's my point though - although not commonly done, there's nothing actually preventing other materials being used as live conductors either. So table 52.3 doesn't necessarily refer to live conductors - but just to copper and aluminium conductors. If I had a copper c.p.c. and steel live conductors, it would seem that table 52.3 would apply to the c.p.c. but not L or N.

- Andy.

OK - I don't agree, but for sure it could be read that way - one more for JPEL 64 to add a few selected words in the next iteration of the fun, fun , fun book -

Regards

OMS

-------------------------
Failure is always an option

Agreed. Perhaps I should start a list - in anticipation of the next DPC.

- Andy.

LoL - will you get anybody to read it, that's the problem I suspect Andy -

Regards

OMS

-------------------------
Failure is always an option

Indeed - but we can but try ....
- Andy.

For sure, Andy - although I'd have to report a singular lack of success by a number of people I know, over the years - particularly in areas that are UK derived rules rather than from CENELEC HD's - the prohibition on aluminium conductors less than 16mm2 is a UK thing - the IEC allows them down to 2.5mm2 I believe - widely allowable under national rules across Europe.

Regards

OMS

-------------------------
Failure is always an option