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Topic Title: These new fangled ideas!
Topic Summary: 1.5mm lighting cable & feeds to switches
Created On: 09 February 2013 06:50 AM
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 12 February 2013 10:19 AM
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AJJewsbury

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

What Regulation is that?

524.1 & table 52.3.

What is the definition of a "power circuit" ? not in BS 7671

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.
 12 February 2013 10:20 AM
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broadgage

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Originally posted by: daveparry1

No reason at all that I can see Rulland, I think some people are taking words from "the red book" too literally, (nothing new there!) what it actually shows on a table in there somewhere is that 1.00mm t/e is to be used for lighting circuits only, my way of thinking is that if an alarm or fan etc. is fed from a lighting circuit it's still a lighting circuit!
Dave.


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.
 12 February 2013 10:31 AM
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AJJewsbury

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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.
 12 February 2013 10:33 AM
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normcall

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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
 12 February 2013 11:28 AM
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potential

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Originally posted by: normcall
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.........................................................


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.
 12 February 2013 12:20 PM
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ebee

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"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
 12 February 2013 12:24 PM
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AJJewsbury

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

(runs for bunker)

- Andy.
 12 February 2013 12:43 PM
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OMS

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Originally posted by: AJJewsbury

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

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Failure is always an option
 12 February 2013 12:54 PM
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AJJewsbury

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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

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.
 12 February 2013 01:18 PM
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OMS

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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

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Failure is always an option
 12 February 2013 01:29 PM
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AJJewsbury

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

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?

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.

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)
 12 February 2013 02:22 PM
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OMS

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Originally posted by: AJJewsbury

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


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

It does, but those further requirements also allow a method of changing the size ?


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?

I might well be - it could be armouring to a single core conductor to say a specialist transformer - and then we have lead or steel CPC's - neither listed in 52.3, so by inference it's still talking about line or live conductors only ?


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.


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).

It doesn't stop neutral being a circuit conductor if present - if it;'s not present, it can't be part of the circuit ?

I guess does the definition of a CPC fit into that of the definition of a circuit



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.

OK - I'll go with that

- Andy.

(edited to fix typo in reg no)


Regards

OMS

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Failure is always an option
 12 February 2013 03:16 PM
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AJJewsbury

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It does, but those further requirements also allow a method of changing the size ?

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 might well be - it could be armouring to a single core conductor to say a specialist transformer - and then we have lead or steel CPC's - neither listed in 52.3, so by inference it's still talking about line or live conductors only ?

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.
 12 February 2013 06:07 PM
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OMS

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Originally posted by: AJJewsbury

It does, but those further requirements also allow a method of changing the size ?


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 was suggesting that either selection or calculation of the CPC was acceptable as that's the further requirement relating to CPC's in Chapter 52 - I'd agree that it could be read as infering a CPC is also subject to the limits of Table 52.3 - it's just that the industry doesn't see it that way (although it has to be said that cable sizes would make it almost impossible not to comply - you don't see that many "power circuits" in 1.5 or 2.5mm2 with a 1.0mm2 CPC - it would tend to be equal size or a minimum of 1.5mm2) - with the exception of 1.5/1.0mm2 T&E of course.

I might well be - it could be armouring to a single core conductor to say a specialist transformer - and then we have lead or steel CPC's - neither listed in 52.3, so by inference it's still talking about line or live conductors only ?


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.

I agree that Table 52.3 refers to live conductors, hence my postulation that it doesn't refer to CPC's as many other materials are permissable as a CPC.


- Andy.


Regards

OMS

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Failure is always an option
 13 February 2013 09:51 AM
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AJJewsbury

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I agree that Table 52.3 refers to live conductors, hence my postulation that it doesn't refer to CPC's as many other materials are permissable as a CPC.

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.
 13 February 2013 11:07 PM
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OMS

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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

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Failure is always an option
 14 February 2013 01:02 PM
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AJJewsbury

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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 -

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

- Andy.
 14 February 2013 01:44 PM
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OMS

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

Regards

OMS

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Failure is always an option
 14 February 2013 02:09 PM
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AJJewsbury

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

Indeed - but we can but try ....
- Andy.
 14 February 2013 02:16 PM
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OMS

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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
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