Right – I've just done the garden up, and in a change from the norm; planned ahead on things like the finishing touches. We've laid wiring for two sets of low voltage lights; the first lot are a load of LED deck lights set into step risers and the like (no decking, I promise!), that are fine. The second lot are from the RING range (B&Q…) and we have created a radial circuit with a 25m cable from the range into which connectors from the lights pierce the two cores to make the connection.

This cable has been well and truly set into the structure of the garden and enters the house close to a socket into which I was going to plug the 20W transformer.

This 12V transformer has about 1m of cable on it and a terminal – with a simple chocolate block arrangement inside. Now, back to normality, I've misread the instructions and they're insistent that all connections, including the initial one (from the transformer to the main circuit cable) must be made outdoors. When I say insistent, they mean it – they only say it about half a dozen times over 3 pages, in CAPS and bold – how could you miss it…?!

I'm stuck now – the cable end's inside, as is the transformer, but I just can't understand what the problem could be? What's going to happen if I connect it up inside the house? Is there a heat / electrocution / some other issue? Sorry if it's obvious, but I'm completely foxed and kicking myself for the schoolboy error. Any help would be very much appreciated.

Cheers in advance. 😳

I ain't a qualified sparkie but that sounds weird to me. heat build up? its the only thing I can think of.

sounds very odd. Especially with a chocolate block connector which even at low voltage does not sound suitable to be outside.

Thanks TJ – they do say the that the connectors can be made more water resistant by wrapping insulating tape, but I've also read that the cores of the main cable are supposedly 'self healing' – if you move a light fitting to another place along the cable, it doesn't affect it down the line.

Heat build up was the only thing I could think of – maybe if it's outside it's less of a combustible issue and there's potentially more free-flowing air around it, but there's no justification or explanation in the literature. I mean – what's to stop you lengthening the cable between the transformer and the first connector (if for example you needed to get it to a plug socket that wasn't within the 1m cable length of the outside) with a similar connector? Surely that would have a similar effect (or lack of)?

Reproducing their IMPORTANT NOTES bit (that I read waaaaay too late… 😳 ) they say: Always remember that the connection from the transformer to the lights must be made outdoors. Do not run low voltage cable in the same trench as, or near to, mains cables.

Don't know if that last bit if pertinent to all of this? I'm going to sit tight for now until I've got a better understanding of it all, but thanks again for the input. I'm just so mad at not reading it properly in the first place…

The last bit

Do not run low voltage cable in the same trench as, or near to, mains cables.

is surely to avoid inadvertently mixing up the mains cable and the LV cable. The results would be sub optimal either way.

The connection one – transformer to lights outdoors does seem like it is trying to reduce risks like heating/fire. Although it might be to avoid cable mixups. You could extend the mains supply to the transformer to let you place it outside, or just leave as is. What's the worst that could happen?

Looks like this is a variation on 'measure twice, cut once' – RTFM 😉

right, yr right the must be connected outdoor thing does sound very odd, quite possiby it is intended to reduce the potential for volt drop if the lights were connected indoors but were a long way off, however as they are led this is unlikely t be the case as they requireittle power anyway.
as for the other, current regulations require mains and extra low voltage to be run seperately to prevent the elv cable from becoming 240v in the event of a fault occuring.

Sounds a bit dodgy that…..i reckon you'll be ok with the connections indoors as if anything gets hot it would be the transformer and that's designed to be indoors. depending on how many lights are on the circuit will depend on the current flowing through the circuit and on a low volt system this can be more than a 240V system but the kit should be designed to handle this, plus led's will be very low wattage…..very minimal risk of a shock as it's 12V from the transformer onwards, so all in all you should be fine. they probably stated the connections outside for maintenance or aesthetic reasons…….I won't give my registration no though just in case!!

Could it be something silly like the connector doesn't meet the regs for internal electrics (kiddies finger sized holes/can be opened without the use of tools) which don't apply when the connection is made outside?