Confused about SWA thickness

[loneranger]

Hi to run some cabling in my garden for some garden lights that purchased from B&Q,

how can i work out how thick the SWA cable needs to be?

 

[PrenticeBoyofDerry]

Need to know the load in watts, the method of installation and the length of the run then go here
http://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html
and you can work it out.
But for lights only likely to be no more than 1.5mm2

 

[ban-all-sheds]

• //www.diynot.com/wiki/electrics:mcbtocable
  
  
• http://www.tlc-direct.co.uk/Book/4.3.1.htm
  
  
• http://web.archive.org/web/20080213151445/http://www.kevinboone.com/cableselection_web.pdf
  
  
• http://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html
  
  
• http://www.tlc-direct.co.uk/Book/5.3.1.htm
  
  
• http://www.tlc-direct.co.uk/Book/7.13.3.htm
  
  
• http://www.tlc-direct.co.uk/Book/8.1.1.htm
  
  
• And if you're in England or Wales: //www.diynot.com/wiki/electrics:part-p
  
  

You should also read these:

• //www.diynot.com/forums/viewtopic.php?p=954537#954537
  
  
• //www.diynot.com/wiki/electrics:swa-gland[/list]and see if your lights are suitable for terminating SWA into. And if not think about how and where you'll join a cable which is suitable to the armoured one, and where you'll run that cable and how you'll protect it.

 

[loneranger]

Thanks for that!

i manged to get the following,

Required Cable Size 1.5 mm
Voltage Drop 3.99 Volts.
Percentage Drop 1.7%
Current Load 1.00 Amps
Max Cable Load* 23.0 Amps

There is any harm in running a 2.5mm cable?

Installation is (40w x 8 lights) underground, and 85m (basically around the edge of the garden)

 

[ban-all-sheds]

What did you input into the calculator to get those results? I'm particularly curious as to how 320W gets you a 1A load.

 

[PrenticeBoyofDerry]

I get this
Required Cable Size 1.5 mm
Voltage Drop 3.67 Volts.
Percentage Drop 1.6%
Current Load 1.00 Amps
Max Cable Load* 22.3 Amps
but it should be more than 1A

 

[ban-all-sheds]

Installation is 320W

.
.
.
Current Load 1.00 Amps
.
.
but it should be more than 1A

OK - I know it's not carrying the full current over the entire 85m, so the voltage drop calculation could be much more sophisticated, but in this case there's no point in practice.

 

[TicklyT]

IIRC someone commented here before that the TLC calculator automatically assumes you have a 3 phase supply if 3 core SWA is selected, leading to such errors.

 

[ban-all-sheds]

 

[ban-all-sheds]

This is interesting (and worrying).

I'd not bothered to change the unit of load from kW to W - I'd just been entering .32, but I realised something must be going on to produce these 1A load figures, so I tried that, and lo....

 

[loneranger]

Hi im goign to buy this cable

Prysmian LV Armoured 3-Core Black 1.5mm² 50m Cable Reel

just wondered what the LV stood for?

is not Low Voltage is it?

 

[electronicsuk]

Yes, it is low voltage:

Extra Low Voltage: AC below 50V and DC below 120V
Low Voltage: 50 - 1000V AC or 120 - 1500V DC
Medium voltage: 1kV - 35kV
High voltage: 35kV - 230kV
Extra-high voltage: >230kV

Also, maybe someone should E-mail TLC about their calculator?

 

[loneranger]

Ah so the cable that i will be rigging up will be fine?

as it will be to the mains 240v

Low Voltage: 50 - 1000V AC or 120 - 1500V DC

 

[empip]

11 x 20W CFL plus a 9W CFL bedside - All running for free !! This cable rocks !!
Looks like the calculator is at least rounding down Amp read out when in non-kW mode.

Just looking at my bookmark for the TLC calculator circa :- 18/04/2004

FWL SAYS Not too accurate Cable calculator http--www.tlc-direct.co.uk-Technical-Charts-VoltageDrop.html

Could have been FWL-Engineer's ghost I guess, he was not specific re. the error(s).

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