Garden lighting - 240v or 12v - pro's and con's?

[^woody^]

I'm planning to have some lights on a fence, and the bulbs will be LED and either 240v Gu10 or 12v MR16 spots.

I would instinctively have preferred 12v low voltage units, but I am finding it difficult to find any in the style I want. But 240v Gu10 lights are much more common.

The circuit will be protected regardless, but is there any reason why a 12v installation would be more preferable to a 240v one?

I'd prefer to run the cable near the top of the fence and then into lights on the posts if that makes a difference.

 

[ericmark]

There are as you say pros and cons, 12 volt is safer as far as electric shocks go, but needs heavier cable, using DC the lamps are often rated 10 ~ 36 volt so no worry about volt drop, but the AC type can show up the volt drop very easy, with an isolation transformer be it 230 to 12 or 230 to 230 the latter is not recommended, water ingress and leakage to earth is not likely to trip the house, however you are not alerted until too late with extra low voltage so the lamp is totally wrecked before you find out, with 12 volt DC you can easy add solar panels and chargers, in both cases terminating into the fitting can be a problem likely you will need junction boxes.

If it were me, since I have a spare 12 volt 200 VA transformer I would use 12 volt, at the price of the transformer if I did not have one spare it would be 230 volt, I would be looking to power any 230 volt lights from a RCBO so that any water ingress it trips but only the outside lights trip, using 12 volt coming of the collective RCD would not be a problem.

With quartz lamps they are water proof with exception of the pins, with LED it is not so cut and dried, with quartz volt drop is a real problem with 12 volt, with LED not as much of a problem. So all in all likely 12 volt is better, but the margin is small.

 

[JBR]

....

The OP was quite clear, either GU10 240v LEDs, or MR16 type 12v LEDs. Yes the GU10 would possibly be MR16 as well but not necessarily.

If it is of any help, I'd like to mention that I have always found your advice to be sensible and worth listening to. I don't mind rudeness if it is meant in a humorous way, but I'm not sure that this is always the case here.

 

[ericmark]

If it is of any help, I'd like to mention that I have always found your advice to be sensible and worth listening to. I don't mind rudeness if it is meant in a humorous way, but I'm not sure that this is always the case here.

I suppose since MR16 means multifaceted reflector 16/8 inch diameter and many of the LED lamps both G5.3 and GU10 have cooling fins so are not 16/8ths of an inch across the lens and also don't have a reflector they are not MR16 lamps.

However I have not seen any post by winston1 on this tread and it is quite plane the question is 12 v 230 volt and really being GU10 or G5.3 has nothing to do with the question.

I personally like the idea of garden lamps being isolated from the house RCD so any water ingress will not cause a freezer to defrost. In essence this means 12 volt, I however can't see the point in 12 volt if the transformer is outside as water can get into the transformer, so in real terms distance makes a lot of difference, in my pocket handkerchief of a garden the power supply can be in doors with lights out doors, however in my friends garden 20 acres of woodland then it is very different. The volt drop could easy be a problem, now we start to look at the type of LED lamp.

With a 24 volt DC power supply and lamps rated 10 ~ 36 volt DC one could run cables to LED lamps over a huge distance without the voltage dropping below 10 volt, however using standard 12 volt really we would not want too long of a run, assuming either 50 Hz or DC we would not have the 3 meter limit of the electronic transformer but we do have to consider cable size, with 230 volt 1 mm flex is really the smallest we can use, with 1 watt lamps even spaced on 12 volt with same flex we are still looking at a lot of cable before we get the voltage down to 10 volt which one would I think consider as being the limit to get a reasonable light output.

However no idea as to if 1 watt or 10 watt lamps are going to be used, or how long the run is, so we can only talk in general terms.

 

[^woody^]

Would I be correct to assume that with a 240v set up and SWA cable, it would need a junction box for each light fitting, whereas a 12v setup could have the [thinner] cable looped in to each fitting?

Max run for one length of cable would be about 14m and 7 light fittings. Probably around 5w per lamp, but maybe 10w let lamp.

 

[JohnW2]

Max run for one length of cable would be about 14m and 7 light fittings. Probably around 5w per lamp, but maybe 10w let lamp.

Roughly what is the total run length (assuming 'looping' from each light to the next one)?

Kind Regards, John

 

[^woody^]

Roughly what is the total run length (assuming 'looping' from each light to the next one)?

Kind Regards, John

Two cables will come out of the outbuilding , one will go one way for 13m and the other another way for 8m. They will either be joined at a transformer or junction box and RCB inside the outbuilding.

 

[ericmark]

12v setup could have the [thinner] cable looped in to each fitting?

Max run for one length of cable would be about 14m and 7 light fittings. Probably around 5w per lamp, but maybe 10w let lamp.

For 12 volt you need thicker cable. 70W = 5.8A and 1mm² will drop 44mV/A/M so assuming even spaced around 1.8 volt drop so last lamp only 10.2 volt not 12 volt, as said it depends on the lamp used, you can get lamps for caravans with a voltage range 10 ~ 36 volt but that is not normal.

Using LED chips in series powered from a driver rather than a fixed voltage source again you can cope with the volt drop, however I expect you want off the shelf ready built lamps. The fittings I have used in the garden had a single gland and needed a round cable to seal in the gland, I had to use a junction box which once wired was filled with petroleum jelly, so there was no room for water to get in. Air expands and contracts more than jelly so tends to suck in water, so no air in box means nothing to suck in water. Don't use grease as some will conduct electric and some has an acid in it.

So 12 volt thick cable to JB say 6mm² so no real volt drop and then 1mm² or less from box to lamps. But I think I would use 230 volt myself, but down to what they look like as much as technical details, after all they are only there to look nice, so what they look like is important.

 

[bernardgreen]

My choice would be ELV, 12 or 24 volt

If the lamps are voltage sensitive ( brightness depending on voltage ) then creating a ring circuit will reduce the visual effect as the dimmer lamps will be midway and not at the far end.

It is an optical illusion, If the end lamps are slightly brighter than the middle lamps then the brain is deceived into thinking the whole string is equally bright