Volt drop, lighting v non lighting

[oscar21]

Why is this still a thing, just done a quick calculation with the TLC volt drop calculator and if its a non lighting circuit the recommended size is 6mm but if there is lighting its saying 10mm. Quite a cost difference.

I get this in the olden days when there were filament lights that would go dim if there wasn't enough voltage or the fluorescent would start strobeing on and off but in today's modern world its all LED lighting and whereas 230v was necessary to light a filament lamp an LED one will work with a little as 3V. Obviously it needs more than 3V for the electonics to work but you get my gist I hope, look on any switch mode power supply and it will usually state a voltage range of something like 100V-230V it will work with.

Isn't it about time this was update to recognise LED lights which they themselves say we must use now.

 

[plugsandsparks]

Why is this still a thing, just done a quick calculation with the TLC volt drop calculator and if its a non lighting circuit the recommended size is 6mm but if there is lighting its saying 10mm. Quite a cost difference.

I get this in the olden days when there were filament lights that would go dim if there wasn't enough voltage or the fluorescent would start strobeing on and off but in today's modern world its all LED lighting and whereas 230v was necessary to light a filament lamp an LED one will work with a little as 3V. Obviously it needs more than 3V for the electonics to work but you get my gist I hope, look on any switch mode power supply and it will usually state a voltage range of something like 100V-230V it will work with.

Isn't it about time this was update to recognise LED lights which they themselves say we must use now.

Certainly a consideration and if i was designing the circuit and was confident that there would be no requirement for any type of discharge lighting AND there were not likely to be high load start currents on motors and the like, i would probably move towards the non lighting side.
However as its a cost reduction opportunity - it flies in the face of the direction of travel for electrical regs

 

[davesparks]

Why is this still a thing, just done a quick calculation with the TLC volt drop calculator and if its a non lighting circuit the recommended size is 6mm but if there is lighting its saying 10mm. Quite a cost difference.

It is still a 'thing' because the laws of physics haven't changed, voltage drop still occurs and the problems associated with it still occur.

Using an online calculator rather than doing the calculation may be contributing to your problem, the online calculator can't make informed decisions about what is or is not an acceptable tolerance on the limits.
If the calculation shows that 6mm has a volt drop of 3.1% then it will recommend 10mm cable whereas any human doing the calculation would go for 6mm.

LED lighting has affected voltage drop due to reduced design current of the circuit. Previously a circuit of 20 downlights could have a design current over 4A whereas now it would be around 0.5A which vastly reduces the volt drop issue.

 

[davesparks]

Certainly a consideration and if i was designing the circuit and was confident that there would be no requirement for any type of discharge lighting AND there were not likely to be high load start currents on motors and the like, i would probably move towards the non lighting side.

How many lighting circuits using LEDs actually end up with a cable having to be over-sized for voltage drop?

By quick calculation if you have a circuit of 20 6W LED lights it could be wired in 1.0mm T&E for a few hundred metres before your need to go up to 1.5mm for VD reasons.