Sign in to follow this  
Barney12

Lighting Radials 1mm or 1.5mm

Recommended Posts

Another pondering question from me :)

 

I'm just thinking about first fix electrics. We're going for radial circuits for all loads, including lighting.

The lighting will be controlled by Cbus Dimmers and Relays back at the cabinet as required.

I've done a few 1st fix wiring jobs over the years (inc three with Cbus) and always used 1.5mm cable to allow for potential loads from say large banks of halogen downlighters.

BUT, with the LED and low voltage being commonplace (and part of regs) I really cant see much point going over 1.00mm now for the lighting radials to each room.

Max run is going to be circa 25m.

All enclosed in service voids (uninsulated) behind pb.

I know the benefits are pretty limited. Perhaps only; 1)Slightly Cheaper 2)Easier to run 3)More room in the cabinet.

Am I missing something?

Share this post


Link to post
Share on other sites
25 minutes ago, Barney12 said:

Another pondering question from me :)

 

I'm just thinking about first fix electrics. We're going for radial circuits for all loads, including lighting.

The lighting will be controlled by Cbus Dimmers and Relays back at the cabinet as required.

I've done a few 1st fix wiring jobs over the years (inc three with Cbus) and always used 1.5mm cable to allow for potential loads from say large banks of halogen downlighters.

BUT, with the LED and low voltage being commonplace (and part of regs) I really cant see much point going over 1.00mm now for the lighting radials to each room.

Max run is going to be circa 25m.

All enclosed in service voids (uninsulated) behind pb.

I know the benefits are pretty limited. Perhaps only; 1)Slightly Cheaper 2)Easier to run 3)More room in the cabinet.

Am I missing something?

 

Do the usual and add up your loads. 1mm should be good but be aware if you run it through more than 500mm of insulation you need to halve the current carrying capacity for any calcs.

 

Edit: How is it all run btw?

Edited by Onoff

Share this post


Link to post
Share on other sites
6 minutes ago, Onoff said:

(I note it's reproduced with kind permission of.....Though I'm prohibited from scanning my regs book and OSG???)

 

Whoops................  Perhaps I shouldn't have scanned mine a day or two ago, then.  :$

Share this post


Link to post
Share on other sites

Personally I never use 1.5 for lighting unless a very long run is involved. Some makes of downlighter just won't fit two 1.5mm cables.

Share this post


Link to post
Share on other sites
7 minutes ago, ProDave said:

Personally I never use 1.5 for lighting unless a very long run is involved. Some makes of downlighter just won't fit two 1.5mm cables.

 

I still have bits of the original lighting here in 2.5mm with 30A jbs! Still, better they used it there than for the hob! :)

Share this post


Link to post
Share on other sites
57 minutes ago, Onoff said:

 

Do the usual and add up your loads. 1mm should be good but be aware if you run it through more than 500mm of insulation you need to halve the current carrying capacity for any calcs.

 

Edit: How is it all run btw?

 

Stolen from Laser

 

Clipsal C-Bus is a microprocessor-based control and management system for small homes to large commercial/industrial installations. It is used to control lighting and other electrical services such as but not limited to pumps, blinds, heating, air conditioning and audio visual devices. Whether simple ON/OFF control of a lighting circuit, or variable (analogue) type control, such as electronic dimmable fluorescent ballasts, C-Bus can be used to easily control virtually any type of electrical load.

Full automation with a powerful programming language is possible with a complete range of touchscreens, logic engines and remote phone/tablet control (iPhone, iPad and Android) via the Wiser range of gateways.

 

Share this post


Link to post
Share on other sites
5 minutes ago, Barney12 said:

 

Stolen from Laser

 

Clipsal C-Bus is a microprocessor-based control and management system for small homes to large commercial/industrial installations. It is used to control lighting and other electrical services such as but not limited to pumps, blinds, heating, air conditioning and audio visual devices. Whether simple ON/OFF control of a lighting circuit, or variable (analogue) type control, such as electronic dimmable fluorescent ballasts, C-Bus can be used to easily control virtually any type of electrical load.

Full automation with a powerful programming language is possible with a complete range of touchscreens, logic engines and remote phone/tablet control (iPhone, iPad and Android) via the Wiser range of gateways.

 

 

Erm...I meant the twin and earth cable...clipped direct, in conduit etc :)

Share this post


Link to post
Share on other sites
3 minutes ago, Onoff said:

 

Erm...I meant the twin and earth cable...clipped direct, in conduit etc :)

 

Sorry :) Clipped to battens in the service void between the pb and the tf.

Share this post


Link to post
Share on other sites
6 hours ago, ProDave said:

Personally I never use 1.5 for lighting unless a very long run is involved. Some makes of downlighter just won't fit two 1.5mm cables.

+1

I almost always run 1.0mm and if it's a big house I'll just do two runs per floor and split it up. 

14 amps for 1.0mm and 18 amps for 1.5mm nominal, less influences like ambient temp and insulation / grouping factors. 

 

This is irrelevant though as that all relates to 'fixed' wiring. If this is an aftermarket lighting controller then the cable runs coming out of it aren't part of the fixed wiring, they're accessories. 

The fixed wiring constraints will terminate at the fused and isolated supply to said controller eg 1x 20a breaker feeding the controller as fixed, and the controller sending accessory live feeds outvto each application ( group of spots / light / led driver / pendant etc ) so the question would then be....what is the individual fused rating of each 'channel' of the controller output ?

Best we get some clarity on exactly what's being asked here before moving on ;)

Share this post


Link to post
Share on other sites
5 hours ago, Nickfromwales said:

+1

I almost always run 1.0mm and if it's a big house I'll just do two runs per floor and split it up. 

14 amps for 1.0mm and 18 amps for 1.5mm nominal, less influences like ambient temp and insulation / grouping factors. 

 

This is irrelevant though as that all relates to 'fixed' wiring. If this is an aftermarket lighting controller then the cable runs coming out of it aren't part of the fixed wiring, they're accessories. 

The fixed wiring constraints will terminate at the fused and isolated supply to said controller eg 1x 20a breaker feeding the controller as fixed, and the controller sending accessory live feeds outvto each application ( group of spots / light / led driver / pendant etc ) so the question would then be....what is the individual fused rating of each 'channel' of the controller output ?

Best we get some clarity on exactly what's being asked here before moving on ;)

 

Cbus outputs are varied but mine will be a mix of 1amp dimmer channels and 10amp relays.

 

Share this post


Link to post
Share on other sites

There's your answer ;). 1.0mm2 will have  loads of headroom, particularly as these will all be independent radial circuits to one zone each. :)

Share this post


Link to post
Share on other sites
40 minutes ago, Nickfromwales said:

The 10a relays will likely / probably have fuses after them too

 

Yes standard practice with C-Bus is to add MCB's after EVERY output. Even the 1amp dimmer channels.

https://www.superlecdirect.com/p-c60hc101-schneider-electric-single-pole-1a-type-c-mcb?gclid=EAIaIQobChMI4_uVwOCz1QIVy1cNCh0AlQgbEAYYASABEgJRHvD_BwE

Share this post


Link to post
Share on other sites
1 hour ago, Temp said:

In case of interest the IEE commissioned a report some time ago on the issue of putting insulation over existing electrical wiring.

 

http://electrical.theiet.org/wiring-matters/15/current-ratings.cfm?type=pdf

 

 

 

Amazing they don't include "laid loose across 100mm of old stuff with another 170mm bunged on top from when the sheds had it on offer".

 

Seriously, where's within insulation?

Share this post


Link to post
Share on other sites

I suspect that, given the high likelihood that any new build will have mainly low energy lighting, lighting circuits never get close to their derated max current.  After all, even a 6A rated 1mm2 lighting radial will be OK for around 1.4kW.  If all the lights in our kitchen/diner were run from a single radial, and all were on at the same time, then the power would be around 80W.  In reality that's three separately controlled sets of lights, with the most powerful group being about 30W.

Share this post


Link to post
Share on other sites

For guidance on the practical application of the regs anyone interested would do well to buy themselves the OSG. 

 

2017-07-31_09-47-28

 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this