After several weeks following these forums and piecing together comments from archived threads concerning SELV lighting I’ve formulated the following plan and would welcome comments as to whether it seems reasonable:
Currently I have a single loop in/out pendant operated by a single gang switch in a 14’ x 11’ ground floor room with plasterboard ceilings with chipboard T&G flooring over.
I’m proposing to install 9 x 35w SELV downlighters, split into two circuits of 5 and 4 and think the best way forward is as follows:
1. Replace the existing ceiling rose with a junction box with the switched live feeding 2x TLC Premium Electronic (Varilight?) 105 VA transformers, each powering 2 X 35 W downlighters.
2. Adding a second junction box to the existing loop in/out live feed, install a 2-gang Varilight IQ touch/remote dimmer (TLC VLIS1402) and route a second switch cable to the new junction box. Connect the switched live to a 150VA Prem Electronic Transformer supplying 3x35 W downlighters and a 105VA transformer supplying the final 2 downlighters.
I reckon 9x35 Watt lights will provide sufficient light, but may want to exchange a couple for 50 W over a desk area if the luminance is not up to scratch and therefore have proposed transformers that could power the same number of 50W lamps. I also want to ensure minimal LV cable runs, hence the use of several transformers/2 circuits. I realise that the general advice is to have one transformer per lamp but cost/practicality mean that this isn’t my preferred option. Therefore, my questions are as follows:
1. Does the setup appear reasonable/practicable?
2. Is there any recommended minimum/maximum distance between the two junction boxes?
3. Does anybody know how many watts per gang this dimmer switch can handle? (Can’t work it out from the TLC pages, but it appears it could be 250-300W per gang, which would be fine).
4. Not having seen any of the transformers in the flesh, I presume the switched live/neutral cable just daisy chains the transformers via the input terminals on the transformers – with the earths joined together to maintain earth continuity - is this correct?
5. Is it OK to power different wattage lamps from the same transformer, or would I need to change all the lamps powered by that transformer.
6. Is there any disadvantage of having “spare capacity” in a transformer, eg total wattage of lamps 70W, transformer 105VA, or lamps 105W, transformer 150VA?
7. If I did decide to have one transformer per lamp and went for the 70VA Prem Electronic transformers, would it be OK to run 5 transformers off one gang of the dimmer and 4 off the other (still obviously with the two circuits, same lamp ratings etc)? (TLC state you can have up to 10 per circuit and to use the lamp ratings, rather than totting up the VA ratings, but I want to make sure the dimmer could operate those transformers over 2 gangs).
Phew, that’s it!
Currently I have a single loop in/out pendant operated by a single gang switch in a 14’ x 11’ ground floor room with plasterboard ceilings with chipboard T&G flooring over.
I’m proposing to install 9 x 35w SELV downlighters, split into two circuits of 5 and 4 and think the best way forward is as follows:
1. Replace the existing ceiling rose with a junction box with the switched live feeding 2x TLC Premium Electronic (Varilight?) 105 VA transformers, each powering 2 X 35 W downlighters.
2. Adding a second junction box to the existing loop in/out live feed, install a 2-gang Varilight IQ touch/remote dimmer (TLC VLIS1402) and route a second switch cable to the new junction box. Connect the switched live to a 150VA Prem Electronic Transformer supplying 3x35 W downlighters and a 105VA transformer supplying the final 2 downlighters.
I reckon 9x35 Watt lights will provide sufficient light, but may want to exchange a couple for 50 W over a desk area if the luminance is not up to scratch and therefore have proposed transformers that could power the same number of 50W lamps. I also want to ensure minimal LV cable runs, hence the use of several transformers/2 circuits. I realise that the general advice is to have one transformer per lamp but cost/practicality mean that this isn’t my preferred option. Therefore, my questions are as follows:
1. Does the setup appear reasonable/practicable?
2. Is there any recommended minimum/maximum distance between the two junction boxes?
3. Does anybody know how many watts per gang this dimmer switch can handle? (Can’t work it out from the TLC pages, but it appears it could be 250-300W per gang, which would be fine).
4. Not having seen any of the transformers in the flesh, I presume the switched live/neutral cable just daisy chains the transformers via the input terminals on the transformers – with the earths joined together to maintain earth continuity - is this correct?
5. Is it OK to power different wattage lamps from the same transformer, or would I need to change all the lamps powered by that transformer.
6. Is there any disadvantage of having “spare capacity” in a transformer, eg total wattage of lamps 70W, transformer 105VA, or lamps 105W, transformer 150VA?
7. If I did decide to have one transformer per lamp and went for the 70VA Prem Electronic transformers, would it be OK to run 5 transformers off one gang of the dimmer and 4 off the other (still obviously with the two circuits, same lamp ratings etc)? (TLC state you can have up to 10 per circuit and to use the lamp ratings, rather than totting up the VA ratings, but I want to make sure the dimmer could operate those transformers over 2 gangs).
Phew, that’s it!