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Topic Title: Lighting cable
Topic Summary: 1.5 & 1.0mm
Created On: 10 January 2019 08:18 PM
Status: Read Only
Linear : Threading : Single : Branch
 Lighting cable   - mikejumper - 10 January 2019 08:18 PM  
 Lighting cable   - broadgage - 10 January 2019 08:28 PM  
 Lighting cable   - sparkingchip - 11 January 2019 09:31 AM  
 Lighting cable   - RB1981 - 10 January 2019 08:35 PM  
 Lighting cable   - aligarjon - 10 January 2019 10:37 PM  
 Lighting cable   - chrispearson - 10 January 2019 10:46 PM  
 Lighting cable   - RB1981 - 10 January 2019 11:08 PM  
 Lighting cable   - mapj1 - 10 January 2019 11:58 PM  
 Lighting cable   - RB1981 - 11 January 2019 12:11 AM  
 Lighting cable   - mikejumper - 13 January 2019 05:55 PM  
 Lighting cable   - RB1981 - 13 January 2019 06:11 PM  
 Lighting cable   - mikejumper - 13 January 2019 07:03 PM  
 Lighting cable   - dustydazzler - 13 January 2019 07:08 PM  
 Lighting cable   - dustydazzler - 11 January 2019 05:40 AM  
 Lighting cable   - broadgage - 11 January 2019 07:11 AM  
 Lighting cable   - Zoomup - 11 January 2019 08:41 AM  
 Lighting cable   - dustydazzler - 11 January 2019 08:53 AM  
 Lighting cable   - Blencathra - 11 January 2019 08:55 AM  
 Lighting cable   - Zoomup - 11 January 2019 09:51 AM  
 Lighting cable   - Blencathra - 11 January 2019 10:47 AM  
 Lighting cable   - dustydazzler - 11 January 2019 09:01 AM  
 Lighting cable   - mapj1 - 11 January 2019 09:15 AM  
 Lighting cable   - Zoomup - 11 January 2019 09:53 AM  
 Lighting cable   - pww235 - 11 January 2019 09:59 AM  
 Lighting cable   - Zoomup - 11 January 2019 10:06 AM  
 Lighting cable   - Zoomup - 11 January 2019 12:10 PM  
 Lighting cable   - Zoomup - 11 January 2019 12:39 PM  
 Lighting cable   - AJJewsbury - 11 January 2019 04:30 PM  
 Lighting cable   - Zoomup - 11 January 2019 06:25 PM  
 Lighting cable   - KFH - 11 January 2019 04:48 PM  
 Lighting cable   - sparkingchip - 11 January 2019 05:51 PM  
 Lighting cable   - aligarjon - 13 January 2019 08:58 PM  
 Lighting cable   - ebee - 14 January 2019 11:05 AM  
 Lighting cable   - sparkingchip - 19 January 2019 10:56 AM  
 Lighting cable   - ebee - 19 January 2019 11:36 AM  
 Lighting cable   - sparkingchip - 19 January 2019 06:35 PM  
 Lighting cable   - sparkingchip - 20 January 2019 11:48 PM  
 Lighting cable   - Zoomup - 11 January 2019 06:17 PM  
 Lighting cable   - broadgage - 11 January 2019 11:11 PM  
 Lighting cable   - dustydazzler - 12 January 2019 09:28 AM  
 Lighting cable   - mapj1 - 12 January 2019 10:56 AM  
 Lighting cable   - Zoomup - 12 January 2019 11:36 AM  
 Lighting cable   - Zoomup - 12 January 2019 11:32 AM  
 Lighting cable   - Legh - 12 January 2019 03:57 PM  
 Lighting cable   - Zoomup - 12 January 2019 04:12 PM  
 Lighting cable   - Legh - 12 January 2019 04:47 PM  
 Lighting cable   - Zoomup - 13 January 2019 04:01 PM  
 Lighting cable   - Legh - 13 January 2019 06:30 PM  
 Lighting cable   - Zoomup - 13 January 2019 06:42 PM  
 Lighting cable   - dustydazzler - 13 January 2019 06:52 PM  
 Lighting cable   - Legh - 13 January 2019 07:01 PM  
 Lighting cable   - Fm - 13 January 2019 08:24 PM  
 Lighting cable   - mikejumper - 13 January 2019 08:43 PM  
 Lighting cable   - Fm - 19 January 2019 04:07 PM  
 Lighting cable   - mikejumper - 19 January 2019 06:01 PM  
 Lighting cable   - dustydazzler - 13 January 2019 08:28 PM  
 Lighting cable   - Zoomup - 20 January 2019 10:11 AM  
 Lighting cable   - ebee - 20 January 2019 12:05 PM  
 Lighting cable   - Legh - 20 January 2019 10:40 PM  
 Lighting cable   - Zoomup - 21 January 2019 02:51 PM  
 Lighting cable   - AJJewsbury - 21 January 2019 03:28 PM  
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 10 January 2019 08:18 PM
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mikejumper

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I'm surprised by the number of installations I come across where 1.5mm T&E has been used for lighting circuits protected by a 6 Amp MCB.

Why, in relatively small domestic installations, would you use a cable nominally rated at 18 Amps for a circuit that most of the time is probably only drawing an amp or two. It wastes copper, makes termination more awkward and costs more.
 10 January 2019 08:28 PM
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broadgage

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I agree.
1.5mm would be a better choice for unusually long circuits to reduce voltage drop.
1.5mm would be better for 10 amp circuits to allow for de-rating if grouped or in thermal insulation.

But for modest length 6 amp circuits it seems extravagant to use 1.5mm.

1.5mm is now the minimum permitted for "power circuits" and some take the cautious view that connection of a fart fan or bell transformer turns a lighting circuit into a power circuit and thus requires 1.5mm.
 11 January 2019 09:31 AM
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sparkingchip

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Cost difference around a fiver per small house?

Andy B
 10 January 2019 08:35 PM
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RB1981

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I completely agree.

However it is always done that way here - in fact wholesalers don't even stock 1mm^2 cable and it would have to be specially ordered (and likely cost more than 1.5mm^2).

I never understand why, if taking that approach, they don't at least use 10A circuit breakers.

Across the border 1.5mm^2 is the minimum permitted cross-sectional area for non-flexible cables for lighting & power, however at least they use 10A MCBs (ET101 still defines them as MCBs) rather than the nonsense in the north of putting it on 6A circuit breakers.

-------------------------
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RECI REC & NICEIC Approved Contractor
 10 January 2019 10:37 PM
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aligarjon

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1.0mm is readily available around here thankfully. I have rarely used 1.5mm, just on long circuits, which is rare for domestics.

Gary

-------------------------
Specialised Subject. The Bleedin Obvious. John Cleese
 10 January 2019 10:46 PM
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chrispearson

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Originally posted by: mikejumper

I'm surprised by the number of installations I come across where 1.5mm T&E has been used for lighting circuits protected by a 6 Amp MCB.

Why, in relatively small domestic installations, would you use a cable nominally rated at 18 Amps for a circuit that most of the time is probably only drawing an amp or two. It wastes copper, makes termination more awkward and costs more.


You wouldn't, although terminating 1.5 sqmm is hardly difficult. However, I agree that 33% of the copper is wasted, which is not 'green' especially with modern LED luminaires.
Originally posted by: RB1981

However it is always done that way here - in fact wholesalers don't even stock 1mm^2 cable and it would have to be specially ordered (and likely cost more than 1.5mm^2).


I don't know about T & E, but that is the minimum size for singles.
 10 January 2019 11:08 PM
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RB1981

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Originally posted by: chrispearson
I don't know about T & E, but that is the minimum size for singles.


Not so much the minimum size as the minimum size available. 1mm^2 singles on a lighting circuit would be compliant, but good luck sourcing them.

-------------------------
Walsh Electrical Services
http://www.walshelectrical.ie/
RECI REC & NICEIC Approved Contractor
 10 January 2019 11:58 PM
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mapj1

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i presume your 1.5mm2 T and E has a full size insulated CPC as well , so can supply a few sockets.

-------------------------
regards Mike
 11 January 2019 12:11 AM
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RB1981

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Originally posted by: mapj1

i presume your 1.5mm2 T and E has a full size insulated CPC as well , so can supply a few sockets.


In the north it is just the ordinary 6242Y cable, so no.

In the south the cable to I.S. 201 does indeed have a full-sized, insulated cpc though. Needless to say the Irish Standard cable costs me substantially more than the British Standard equivalent.

It certainly wouldn't be normal practice to use the 1.5mm^2 to supply socket outlets though!

-------------------------
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http://www.walshelectrical.ie/
RECI REC & NICEIC Approved Contractor
 13 January 2019 05:55 PM
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mikejumper

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Originally posted by: RB1981
In the south the cable to I.S. 201 does indeed have a full-sized, insulated cpc though.

Is it flat T&E or round?
 13 January 2019 06:11 PM
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RB1981

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Originally posted by: mikejumper

Originally posted by: RB1981

In the south the cable to I.S. 201 does indeed have a full-sized, insulated cpc though.



Is it flat T&E or round?


It's flat.

And with brown & Earth or blue & Earth instead of being round like the BS equivalent it is also flat.

-------------------------
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 13 January 2019 07:03 PM
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mikejumper

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Originally posted by: RB1981

Originally posted by: mikejumper



Originally posted by: RB1981



In the south the cable to I.S. 201 does indeed have a full-sized, insulated cpc though.





Is it flat T&E or round?


It's flat.

And with brown & Earth or blue & Earth instead of being round like the BS equivalent it is also flat.

Thanks RB, I thought might be more like the round stuff I've seen in France.
I would like to see 1.0mm T&E available here with an insulated earth.
 13 January 2019 07:08 PM
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dustydazzler

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Originally posted by: mikejumper

Originally posted by: RB1981



Originally posted by: mikejumper







Originally posted by: RB1981







In the south the cable to I.S. 201 does indeed have a full-sized, insulated cpc though.











Is it flat T&E or round?




It's flat.



And with brown & Earth or blue & Earth instead of being round like the BS equivalent it is also flat.


Thanks RB, I thought might be more like the round stuff I've seen in France.

I would like to see 1.0mm T&E available here with an insulated earth.



You can buy 3c 4c 5c in 1mm 'solid' core flex over here
 11 January 2019 05:40 AM
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dustydazzler

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1.5 for sochets

You cheeky badgers
 11 January 2019 07:11 AM
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broadgage

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Of course in work places with a long hour lighting load, larger cables might pay for themselves via reduced losses.

Consider as an example a 1kW lighting circuit in which the losses are reduced from 3% to 2% by use of larger cable.

Saving 1% is 10 watts, or perhaps 50Kwh a year for long hours of use. 50Kwh is worth about £7.50.
In twenty years and presuming no increases in energy cost, £150 has been saved, more than enough to pay for larger cables.
 11 January 2019 08:41 AM
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Zoomup

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1.0mm2 T&E is more than adequate for domestic lighting circuits these days, especially considering that we are changing our lighting to more energy efficient types. )But even with old filamment lamps it was still o.k.). 1.5mm2 is a waste of money for most domestic lighting jobs. I have never found difficulty in obtaining 1.0mm2 T&E cable.

Z.
 11 January 2019 08:53 AM
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dustydazzler

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I personally used to exclusively use 1mm on my own jobs , I just found it much nicer to terminate in those fancy wall lights and flush fittings etc

But when I subbied would often be given rolls of 1.5 to wire the lights in new builds etc

Not my money so never really questioned it
 11 January 2019 08:55 AM
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Blencathra

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When I was rewiring council estates, the spec was 1.5 for lighting & 16mm tails
 11 January 2019 09:51 AM
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Zoomup

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Originally posted by: Blencathra

When I was rewiring council estates, the spec was 1.5 for lighting & 16mm tails


Yep, there was a perceived potential abuse of lighting circuits so 1.5mm2 was specified. Possibly to be more robust when aluminium kitchen foil was wrapped around a blown cartidge fuse in the fuse box.

Z.
 11 January 2019 10:47 AM
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Blencathra

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Originally posted by: Zoomup

Originally posted by: Blencathra



When I was rewiring council estates, the spec was 1.5 for lighting & 16mm tails




Yep, there was a perceived potential abuse of lighting circuits so 1.5mm2 was specified. Possibly to be more robust when aluminium kitchen foil was wrapped around a blown cartidge fuse in the fuse box.



Z.


Crabtree starbreakers AFAIK
 11 January 2019 09:01 AM
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dustydazzler

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Yes 16mm were extremely common in my area
 11 January 2019 09:15 AM
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mapj1

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well from a currant carrying perspective ('ampacity' to our friends with a funny accent, the welsh...) modern double insulated LED lights could probably be wired in speaker flex.
But there is another problem, that of being robust against mice in the loft or Dangerous Dave's DIY, so a minimum has to be agreed, it just happens that different local styles have emerged as to what that is.
I don't really have a problem with a 13A socket or a 16A radial on 1.5mm clipped direct, and it does side step this question about things like bathroom fans and mirror heaters and so forth not being 'lighting circuits'.

-------------------------
regards Mike
 11 January 2019 09:53 AM
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Zoomup

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Cost in extra time fiddling about with the bigger conductors, substantial.

Z.
 11 January 2019 09:59 AM
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pww235

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Is it really that much of a difference Z? ~0.2mm difference in core diameter.

P
 11 January 2019 10:06 AM
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Zoomup

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Originally posted by: pww235

Is it really that much of a difference Z? ~0.2mm difference in core diameter.



P


I notice a difference. The 1.5mm2 fights back and is more difficult to dress into back boxes. Also 1.0mm2 is easier when connecting two conductors into switch terminals such as with two-way switching. It is just a personal choice for me. And 1.5mm2 three core and earth cable is less manageable than 1.0mm2 three core and earth. Why use a cable bigger than needed?

Z.
 11 January 2019 12:10 PM
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Zoomup

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Back in the days of fuse wire it was found that people would renew blown fuses with larger wire or fit a paper clip in the carrier. So, back then when M.C.B.s were not available at a sensible price, or even at all, councils had cartridge fuses fitted to fuse boxes in council houses. As the fuses were physically different in size according to rating it was assumed that the wrong fuse could not be fitted into a carrier. The smallest being 5 Amp and the common largest in size being a 30 Amp cartridge fuse. But some tenants would wrap kitchen foil around a blown cartridge fuse to save money, or where a new fuse wasn't immediately available. Rewires may have had new consumer units fitted with M.C.B.s, but presumably the 1.5mm2 lighting cable may have remained in the house, or the size retained in the rewire as it was traditionally used due to its robustness and ability to withstand abuse to a certain extent People may have added heaters to the lighting circuit years ago or run appliances from lighting points using B.C. plugs or adaptors.

Z.
 11 January 2019 12:39 PM
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Zoomup

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In the 50s and 60s two way B.C. lamp adaptors were in use in the U.K. They fitted in a ceiling light holder and allowed a bulb to be inserted in one of the outlets and the other outlet could be used for an appliance such as a clothes iron. There was no earthing provision so the earth of the clothes iron was left unconnected, a dangerous arrangement. These devices could cause overloading of lighting circuits if too many appliances were connected at once. This in the days of fuse wire and cartridge fuses.

http://www.flameport.com/elect...uble_BS52_adaptor.cs4



Z.
 11 January 2019 04:30 PM
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AJJewsbury

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In the 50s and 60s two way B.C. lamp adaptors were in use in the U.K.

I'm sure they were available a lot earlier and later than that - I remember shelf fulls of them in Woolworths when I was a kid (along with all kinds of round/flat pin adaptors) and that wasn't any earlier than the mid 1970s.

- Andy.
 11 January 2019 06:25 PM
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Zoomup

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Originally posted by: AJJewsbury

In the 50s and 60s two way B.C. lamp adaptors were in use in the U.K.


I'm sure they were available a lot earlier and later than that - I remember shelf fulls of them in Woolworths when I was a kid (along with all kinds of round/flat pin adaptors) and that wasn't any earlier than the mid 1970s.



- Andy.


Quite possibly........................ but B.S. 52:1963 covers the B.C. adaptors. I am too young to remember the 1940s though. By the 70s most homes had sufficient 13 Amp. sockets to supply appliances such as clothes irons or had trailing sockets available. The trailing clothes' iron flex from the swinging ceiling light was a thing of the past in most homes.

Z.
 11 January 2019 04:48 PM
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KFH

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I don't like using 1.0 as I find it often breaks at the accessory even when doubled. The small extra cost of 1.5 makes it worthwhile in my opinion for a more robust connection. Perhaps I am just to heavy handed.

I have a soldering iron with a bayonet plug on the end. The rubber flex has seen much better days so I don't think I will be tempted to use it anytime soon.

I certainly used the double adaptors in the 50's and can remember my mother and others ironing using an iron connected to one. As an agile youngster I was expected to climb on the chair to plug it in/unplug it. Using more than one double adaptor was not uncommon.
 11 January 2019 05:51 PM
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sparkingchip

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Originally posted by: KFH

I don't like using 1.0 as I find it often breaks at the accessory even when doubled. The small extra cost of 1.5 makes it worthwhile in my opinion for a more robust connection. Perhaps I am just to heavy handed.


Which is why 1.0 mm cable cannot be used for emergency lighting installation.

Andy Betteridge
 13 January 2019 08:58 PM
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aligarjon

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Originally posted by: sparkingchip

Originally posted by: KFH



I don't like using 1.0 as I find it often breaks at the accessory even when doubled. The small extra cost of 1.5 makes it worthwhile in my opinion for a more robust connection. Perhaps I am just to heavy handed.




Which is why 1.0 mm cable cannot be used for emergency lighting installation.



Andy Betteridge


I didn't know this. I haven't done any form of emergency lighting for years. Can they be fed from a 1.0mm circuit in 1.5mm or would they have to be run back to the CU if you were protecting a 1.0mm circuit ?


Gary

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 14 January 2019 11:05 AM
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ebee

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I am a 1.0er definately not a 1.5er

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Regards,
Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik
 19 January 2019 10:56 AM
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sparkingchip

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How if it is an extra-low voltage lighting installation we need to consider 715.524.201 which requires luminaries that are suspended on flexes to have 4.0 mm conductors in that flex for mechanical reasons.
 19 January 2019 11:36 AM
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ebee

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Hi Sparkingchip.
I was refferering to current carrying etc etc for the majority of circuits I do and making off by folding double the live conductors.
Mostly domestic.
Ie to a rose or other similar junction.
Strain on flexes or whatever is another issue to what I was thinking and therefore larger csa might come into play

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

Knotted cables cause Lumpy Lektrik
 19 January 2019 06:35 PM
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sparkingchip

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Originally posted by: ebee

Hi Sparkingchip.

I was refferering to current carrying etc etc for the majority of circuits I do and making off by folding double the live conductors.

Mostly domestic.

Ie to a rose or other similar junction.

Strain on flexes or whatever is another issue to what I was thinking and therefore larger csa might come into play


I know that, I was actually looking for a regulated that requires equipment such as SELV bathroom extractor fans should be wired in 1.5 mm twin and earth on the 12 volt circuit, I'm sure it's there somewhere, just can not remember where at the moment.

1.0 mm isn't a universal size for domestic and commercial lighting circuits and what is connected to them there are several situations where you need to up the conductor size to 1.5 mm.
Andy B
 20 January 2019 11:48 PM
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sparkingchip

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Originally posted by: sparkingchip

How if it is an extra-low voltage lighting installation we need to consider 715.524.201 which requires luminaries that are suspended on flexes to have 4.0 mm conductors in that flex for mechanical reasons.


I have solved the issue of what has been confusing me.

My logical approach to wiring the extra low voltage circuit of ELV bathroom and shower room fans was to do as you need to do for ELV lighting.

First look at 715.524.201 in the 18th Edition of BS7671:2018 then have a look at the same regulation in the 17th Edition of BS7671:2008:Amd 3.

In the last edition of the wiring regs it read:
The minimum cross sectional area of the extra-low conductors shall be:
(i) 1.5 mm2 copper, but in the case of flexible cables with a maximum length of 3 m a cross-sectional area of 1 mm2 copper may be used.

I know that applied to lighting, but my logic was that a ELV fan installation is just the same.

Andy Betteridge
 11 January 2019 06:17 PM
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Zoomup

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I never have any problems with 1.0mm2 breaking if it is stripped carefully. It may break at terminations if the copper is nicked by careless insulation removal. Solid copper conductors can all break if nicked, even 1.5 or 2.5mm2. Stranded conductors seemed to be more reliable as compared to single solid conductors.

Z.
 11 January 2019 11:11 PM
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broadgage

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BC adaptors were in general use into the 1980s in older properties that often only had one 13 amp socket in bedrooms, and two in living rooms.
3 way versions existed, for a light bulb, the clothes iron, and a radio for example.
My late grandfather had a lead light with a BC adaptor and many yards of flex, it was plugged into the bathroom light and used to light the loft when needed.

These adaptors still have their uses, I used some a few weeks ago for Christmas lights in the local pub.
 12 January 2019 09:28 AM
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dustydazzler

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I used to have a bc adaptor with about 10m of flex on it attached to an old cage type lead light with large clamp on it take into lofts.
Very handy
 12 January 2019 10:56 AM
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mapj1

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As a point of note BS52 was the right number from about 1910 to mid 1981, as the standard got updated without changing the number, however the 1933 edition is the earliest of many outdated versions you can get from the BSI in PDF format.

Actually compared to the standard for lamp holders, the wiring regs are positively a model of stability.
BS 52:1933 Bayonet lamp-caps and metal cased bayonet lampholders not exceeding 250 volts
BS 52:1936 Bayonet lamp-caps. Lampholders and lampholder-plugs (B.C. adaptors) for voltages not exceeding 250 volts
BS 52:1941. -"-
BS 52:1952 Bayonet lamp-caps. Lampholders and lampholder-plugs (B.C. adaptors)
BS 52:1963 Specification for bayonet lamp-caps lampholders and B.C. adaptors (lampholder plugs)
BS 5042-1:1981 Specification for lampholders and starterholders. Bayonet lampholders
BS 5042:1987 Specification for bayonet lampholders
BS EN 61184:1995 -"-
BS EN 61184:1997, IEC 61184:1997 -"-
BS EN 61184:2008 -"-
BS EN 61184:2011 -"-
The latest is BS EN 61184:2017 Bayonet lampholders

And its already under review again, so clearly things are changing fast.
A similar thread of documents exists for edison screw lampholders, the connections for florry tubes, ELV lamps, aircraft lamps, linear lamps..

I suppose we should be pleased that we are not expected to buy up to date copies of these as well as of BS7671, all at a hundred quid or so a pop.

-------------------------
regards Mike
 12 January 2019 11:36 AM
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Zoomup

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Originally posted by: mapj1

As a point of note BS52 was the right number from about 1910 to mid 1981, as the standard got updated without changing the number, however the 1933 edition is the earliest of many outdated versions you can get from the BSI in PDF format.



Actually compared to the standard for lamp holders, the wiring regs are positively a model of stability.

BS 52:1933 Bayonet lamp-caps and metal cased bayonet lampholders not exceeding 250 volts

BS 52:1936 Bayonet lamp-caps. Lampholders and lampholder-plugs (B.C. adaptors) for voltages not exceeding 250 volts

BS 52:1941. -"-

BS 52:1952 Bayonet lamp-caps. Lampholders and lampholder-plugs (B.C. adaptors)

BS 52:1963 Specification for bayonet lamp-caps lampholders and B.C. adaptors (lampholder plugs)

BS 5042-1:1981 Specification for lampholders and starterholders. Bayonet lampholders

BS 5042:1987 Specification for bayonet lampholders

BS EN 61184:1995 -"-

BS EN 61184:1997, IEC 61184:1997 -"-

BS EN 61184:2008 -"-

BS EN 61184:2011 -"-

The latest is BS EN 61184:2017 Bayonet lampholders



And its already under review again, so clearly things are changing fast.

A similar thread of documents exists for edison screw lampholders, the connections for florry tubes, ELV lamps, aircraft lamps, linear lamps..



I suppose we should be pleased that we are not expected to buy up to date copies of these as well as of BS7671, all at a hundred quid or so a pop.


I look forward to discussing that with my new girlfriend tonight over drinks at The Dog and Duck. I am normally stuck for words and subject matter so that info is very helpful.

Bye,

Z.
 12 January 2019 11:32 AM
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Zoomup

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For Sale.

Tea chest of B.C. brown plugs. Slightly dusty. Some spider and fly parts' content. Good condition. New unused old stock.

£5.00 per pound or £20.00 per gross or 2/6d each. Buyer collects.

Tel. Grimsby 227.

Z.
 12 January 2019 03:57 PM
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Legh

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If I remember rightly you would not want to use 1.0mm2 singles for lighting ......why? your weekend quiz question...

I had the same debate with a colleague once and it was resolved by demonstrating basic cable calcs even when derating by 50% the conductor size is still compliant...

Legh

-------------------------

http://www.leghrichardson.co.uk

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 12 January 2019 04:12 PM
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Originally posted by: Legh

If I remember rightly you would not want to use 1.0mm2 singles for lighting ......why? your weekend quiz question...



I had the same debate with a colleague once and it was resolved by demonstrating basic cable calcs even when derating by 50% the conductor size is still compliant...



Legh


Hello Legh,
I don't recall saying that I would not use 1.0mm2 T&E for domestic lighting circuits. I have used it for years with 5 Amp fuses or 6 Amp M.C.B.s. Perhaps you could post the quote to refresh my memory. Recently I have been saying that there is no need for normal domestic lighting circuits to have 1.5mm2 conductors. 1.5mm2 cables may be needed for long runs or larger loads though.

Z.
 12 January 2019 04:47 PM
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Legh

Posts: 4427
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Nothing wrong with 1.0mm2 single core Twin & E for lighting, in fact I would recomend it for smal/domestic installations. However, I would not recomend 1.0mm2 single core singles when installed in conduit . Why?

Legh

-------------------------

http://www.leghrichardson.co.uk

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 13 January 2019 04:01 PM
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Originally posted by: Legh

Nothing wrong with 1.0mm2 single core Twin & E for lighting, in fact I would recomend it for smal/domestic installations. However, I would not recomend 1.0mm2 single core singles when installed in conduit . Why?



Legh


What was the answer provided at the time Legh?

Z.
 13 January 2019 06:30 PM
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Legh

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"What was the answer provided at the time Legh?"

The answer given by RB1981 states that 1.0mm2 singles appears now to be unavailable, not that I've attempted to purchase it in the last 30 years. You really wouldn't want to use it in conduit.

Legh

-------------------------

http://www.leghrichardson.co.uk

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 13 January 2019 06:42 PM
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Originally posted by: Legh

"What was the answer provided at the time Legh?"



The answer given by RB1981 states that 1.0mm2 singles appears now to be unavailable, not that I've attempted to purchase it in the last 30 years. You really wouldn't want to use it in conduit.



Legh


1.0mm2 6491X is still listed in the C.P.C. catalogue. I have even been known to strip down 1.0mm2 T&E flat cable when pushed to get short lengths for conduit use. I can see no problem using 1.0mm2 singles in conduit, taking its physical strength limitation into account and limiting run's length.

Z.
 13 January 2019 06:52 PM
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dustydazzler

Posts: 3068
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I still have a roll of 1mm single core in red

Had it for donkeys years
 13 January 2019 07:01 PM
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Legh

Posts: 4427
Joined: 17 December 2004

The stuff lacks flexibility and kinks far too easily and when unrolling several rolls at a time to feed up your pipes it kinks and jams unless there is somebody carefully feeding the end.

Legh

-------------------------

http://www.leghrichardson.co.uk

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 13 January 2019 08:24 PM
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Fm

Posts: 2032
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Never used 1.0mm.
My company during my apprenticeship always used 1.5mm
I use 1.5mm now
 13 January 2019 08:43 PM
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mikejumper

Posts: 2810
Joined: 14 December 2006

Originally posted by: Fm

Never used 1.0mm.

My company during my apprenticeship always used 1.5mm

I use 1.5mm now

So could you be persuaded to use 1.0mm?
 19 January 2019 04:07 PM
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Fm

Posts: 2032
Joined: 24 August 2011

Originally posted by: mikejumper

Originally posted by: Fm



Never used 1.0mm.



My company during my apprenticeship always used 1.5mm



I use 1.5mm now


So could you be persuaded to use 1.0mm?


Nope, just wired my extension and it's 1.5mm for me.
 19 January 2019 06:01 PM
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mikejumper

Posts: 2810
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Originally posted by: Fm

Originally posted by: mikejumper



Originally posted by: Fm







Never used 1.0mm.







My company during my apprenticeship always used 1.5mm







I use 1.5mm now




So could you be persuaded to use 1.0mm?




Nope, just wired my extension and it's 1.5mm for me.

You won't be in the 1.0mm members club Fm, you'll be an outsider, are you sure you're happy with that, there's still time to change your mind.
 13 January 2019 08:28 PM
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dustydazzler

Posts: 3068
Joined: 19 January 2016

Would anyone have an issue putting 1mm flex on a plug top with a 5a fuse ?

If not then why would anyone have an issue putting 1mm on a 6a mcb

1.5 is overkill on all but the largest of domestic dwellings
 20 January 2019 10:11 AM
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Zoomup

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A 12 Volt extractor fan might typically be rated at 30VA. So 1.0mm2 cable will be more than adequate in most domestic situations as a supply cable. A current of 2.5 to 3 Amps. at 12 Volts.

http://www.greenbrook.co.uk/product-pdfs/12VFC_Ins.pdf

Z.
 20 January 2019 12:05 PM
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ebee

Posts: 6735
Joined: 02 December 2004

If it`s running a fan it must be 1.5 min. Cos its a power cct.
Add a light to it and its a lighting cct with a fan added so 1.0 is ok .


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Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik
 20 January 2019 10:40 PM
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Legh

Posts: 4427
Joined: 17 December 2004

Would anyone have an issue putting 1mm flex on a plug top with a 5a fuse ?
If not then why would anyone have an issue putting 1mm on a 6a mcb 1.5 is overkill on all but the largest of domestic dwellings


Have you ever used several 1.0mm2 solid core singles and then tried to stuff them up a pipe (20mm conduit)? That is, in the same manner when using 1.5mm2 flexible singles?

Worth a shot to be convinced, I suspect.

Legh

-------------------------

http://www.leghrichardson.co.uk

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 21 January 2019 02:51 PM
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Originally posted by: ebee

If it`s running a fan it must be 1.5 min. Cos its a power cct.

Add a light to it and its a lighting cct with a fan added so 1.0 is ok .



So a shower extractor fan with an integral light is a lighting load then

It is a pity that B.S. 7671 does not have a definition for a "Power Circuit".

Would I have to supply a single door bell transformer internally fused at 0.08 Amps in 1.5mm2?

Z.
 21 January 2019 03:28 PM
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AJJewsbury

Posts: 17795
Joined: 13 August 2003

Would I have to supply a single door bell transformer internally fused at 0.08 Amps in 1.5mm2?

Depends if you classify it as a power circuit, or a signalling and control circuit, and whether it's in flex or not.
- Andy.
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