ELV lighting

[studentspark]

300 watt ELV light
cable run 6.5m
That comes out at about 16mm2 cable

Seems excessive, but...

Any comments on this appreciated

 

[RF Lighting]

Whats the supply voltage?

 

[studentspark]

12 v

 

[EFLImpudence]

What exactly is your question?

Mine is "Why?"

 

[RF Lighting]

300 divide 12 = 25

Design current = 25A

Maximum permitted vd for lighting is 3% = 0.36V

0.36V divide by 6.5 = 55.38mV This is the most voltage you can drop per meter

55.38mV divide by 25A = 2.21mV This is the maximum volts drop per ampere per meter of the cable you need.

16.0mm² cable has a vd of 2.8 mV/A/m so is just ok.

Can you not run the lv to the point of utilisation before converting to elv?

 

[studentspark]

Thanks RF

Its for a pool light so Transformer has to be outside the zones.
Don't really want to bury the transformer, and would rather put in an enclosure hence the 6.5 m

 

[RF Lighting]

To be honest with a single lamp you might be able to get away with a higher vd. I dare say in the real world youre not going to notice a drop of a volt or so.

Try mocking up the lights with 6.5m of 10mil and see how well the lights perform.

Is there a facility to terminate such a big cable into your light?

 

[studentspark]

I am trying to put right badly installed pool lighting
The in pool light transformer was 50 cm from the pool edge . That is the mains supply!

The light has 4mm cable to the enclosure.
I plan to run ELV to this.

 

[RF Lighting]

I think 4.0mm² might be pushing a bit TBH, but if that's what you're stuck with all you can do is try it.

 

[studentspark]

The 4mm is the last 50cm to the light it self.
It will be 16mm to the connection to the 4mm.


Thanks again for your time tonight. really appreciated.

 

[RF Lighting]

Oh right, I think you should be ok then

Years ago me and my mate Chris ran 10 of those 10W capsule fittings in 2.5 and they were really dim by the end We were both young and only calculated the increased current for ELV (hence the 2.5). We never even thought about vd

 

[ericmark]

I would for a single lamp compensate for volt drop rather than trying to limit it. I had a line of ELV lamps to install over a couple of miles and the transformers were wired in series. Aircraft ground lights.

Problem is were many bulbs add to 300W so if one blows volts rise. Single bulb no real problem just use a higher supply volts. Clearly needs a transformer not an inverter so one can adjust the tapping.

 

[ban-all-sheds]

What's the existing cable to the existing transformer?

It would mean sourcing non-standard components, but if at the outside-zone end you dropped to 48V, and then at the pool edge dropped to 12V you could re-use the existing cable currently used to supply LV to the light, which might save a lot of digging and making good, and be cheaper and easier overall.

 

[studentspark]

I dug the transformer out as it was 50 cm from pool,


Ran new 2.5 SWA from pool house to a enclosure for the 300w transformer then 16 mm2 to pool light

The original was 1.5 rubber (H07 )

Hard job but have found out I am quite good at cutting and relaying turf and relaying paving slabs.