Low Voltage lighting cable size

Hi. I'm planning to connect 4x 50w lv downlights using 2 105va dimmable multi outlet transformers connected to 2 lights each. All cabling will be in the loft, replacing an existing ceiling rose fitting. Controlled via a single dimmer switch.

I have read various articles about the importance of cable size and used the lv cable size calculator on tlc-direct

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plan to connect each transformer to a junction box in parallel and connect 2 lights to each JB in parallel. Estimated cable length of 2m between the JB and each light.

  1. Is the total load 100w or 50w in this setup and what would you advise cable size to be?

  1. If 1.5 mm2 is recommended, for example, then would using a thicker cable such as 2.5mm2 cause a problem? Would a overestimation of cable size impact the life of the bulbs?

  2. If the transformers need to be connected to a JB using additional cable to that supplied (say 2m also) would standard 2.5mm2 power cable be suitable?

  1. I've heard some worrying stories about transformer reliability - any recommendations on a good reliable make?

  2. Would a max 250va dimmer switch be suitable for this setup?

  1. Has anyone any advice on improving the angle of light from lv lights but avoiding glare on computer monitors. I'm thinking of 60 degree beam MR16 lights to spread light as much as possible but concerned about glare... so many worries...

Thanks in advice for any advice offered, Rupertb

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rupertb
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The load from the transformer to the junction box is 100w. The load in each cable to a lamp from the junction box is 50w. I would use 2.5mm between the transformer and the box, and 1.5mm to the lamps.

Make it as fat as you like - you can't have less than zero voltage drop, and zero is fine!

Yes.

Dunno!

Possibly - but you may need to use expensive dimmers and transformers to make them work acceptably. I bought "fully dimmable" transformers and "compatible" dimmers from Screwfix, and the transformers buzzed something wrotten when connected to the dimmers - even on the max power setting. In the end, I sent the dimmers back. The lamps are fine undimmed. [I have 3 banks of 4 x 50w lamps in my L-shaped lounge - with each bank being separately switchable. Along with some wall lights, this gives a fairly flexible lighting setup without requiring dimmers].

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