12 v led volt drop? - Wiring and the Regulations BS 7671 - IET EngX - IET EngX

12 v led volt drop?

I'm having one of those moments where I cant work out anything.

12 volt led driver feeding garden lighting,  run of 40 metres is proposed. 80 watts total load, led driver is rated at 150 watts. Is it the 12 volt ampage for the calculation, or the mains? I am presuming the 12 volts for the calculation, which gives 7 amps current draw, which , on 1.5mm cable, gives a near 60% volt drop.

Does that look about right?

If so, it is going to need either mains voltage outside lights, or local transformers.

Thanks.

Parents
  • As a rule of thumb the distance for any system to change from being volt drop limited to cable current rating limited is (to within a factor of 1 or 2) the same as the voltage. For systems transmitting much power that also ends up being close to the economic limit for changing voltage as well

    So. 12m for 12V systems (ah.... now then !)

    230m (or maybe 400m) for LV mains,

    (ever wondered why 400/690 is used in bigger factories with sheds of hanger size ?)

    a few tens for km for 11kv lines

    etc/

    You are well off the very hard end of getting impractical for 12V.

    Personally I would not try and send 12V that far and expect most of it to arrive, except for a very low current signalling system, Any chance of re-adjusting to be a series connection, or center  feeding or supplying at 110V or something ?

    Mike.

Reply
  • As a rule of thumb the distance for any system to change from being volt drop limited to cable current rating limited is (to within a factor of 1 or 2) the same as the voltage. For systems transmitting much power that also ends up being close to the economic limit for changing voltage as well

    So. 12m for 12V systems (ah.... now then !)

    230m (or maybe 400m) for LV mains,

    (ever wondered why 400/690 is used in bigger factories with sheds of hanger size ?)

    a few tens for km for 11kv lines

    etc/

    You are well off the very hard end of getting impractical for 12V.

    Personally I would not try and send 12V that far and expect most of it to arrive, except for a very low current signalling system, Any chance of re-adjusting to be a series connection, or center  feeding or supplying at 110V or something ?

    Mike.

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