Re: Extra Low volt switching for lighting

[efficiencyman]

Re: Extra Low volt switching for lighting

What regulations are there for extra low voltage controlled 12 Volt lighting. Also are there regs for any type of low volt DC switching from 12 volt battery (solar charged) off-grid LED lighting ?
The control unit is home brew with infra red handheld remotes & some areas are wired in alarm cable as the control signal is only a few milliamps.
The LED lights are switched by relays and wired in 1-0 mm cable to supply 12 volt to the rooms, mostly MR16 5w LED`s

 

[Adam W]

Being ELV I think you can pretty much use what you like, such as those little switches most people here probably had a play with at primary school.
Personally I'd aim towards ordinary light switches (obviously dimmer switches won't work) so it's obvious what they're for.

As regards the cable, I'm not sure what you've done with this control system, but for conventionally wired lighting you'd probably want to use something big enough to counter volt drop.

 

[Gavin A]

Being ELV I think you can pretty much use what you like, such as those little switches most people here probably had a play with at primary school.
Personally I'd aim towards ordinary light switches (obviously dimmer switches won't work) so it's obvious what they're for.

As regards the cable, I'm not sure what you've done with this control system, but for conventionally wired lighting you'd probably want to use something big enough to counter volt drop.

LED mind, so the power will be pretty low for the volt drop calcs

 

[solarfred]

You cannot go far at 12v using small 1mm cable into LED as they start to grumble. High pitched whistling? I tend to go for 24v to avoid the need for heavier cable. At 12v I run short lengths of 1mm to each lamp from a junction box carrying heavier cable. I mostly use LED tubes so running 16w each lamp. Try it with a length of cable/battery and a lamp to check before you wire it all up as quality of lamps may have a bearing too?

As for regulations it is something I have been wondering from an insurance standpoint. If you wire according to standard regs. then any problems should be covered by insurance but if there are no regs. what stance does the insurance take? Should it be disclosed to insurers? You need to have your own professional liability cover anyway just in case.
Having recently had a very serious incident with a "dead" battery coming to life and giving off large volumes of hydrogen I am far more aware that low voltage does not mean risk free.

 

[BruceB]

To answer the original question, BS7671 describes its scope at Part 1 Chapter 11. It basically includes all the wiring you are likely to find in domestic premises except that specifically covered by appliance standards. So all ELV circuits, telephone wiring and network wiring falls within the regs, albeit in many ways they are not so demanding at ELV. In some ways they are more demanding though.

As an example 559.11 applies to ELV lighting circuits and specifically:
"559.11.5.2 The minimum cross-sectional area of the extra-low voltage 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
(ii) 4 mm2 copper in the case of suspended flexible cables or insulated conductors, for mechanical reasons
(iii) 4 mm2 copper in the case of composite cables consisting of braided tinned copper outer sheath, having a material of high tensile strength inner core."