In article ,
Jim S writes:
What, exactly, is the situation regarding the phasing out of tungsten
lightbulbs?
All my main room lights are on dimmer switches so do I fill my spare
bedroom with bulbs for the future?

Across the extended family, we have two rooms with dimmers.

1) Central light taking 5 x SES 25W candles.

There's an 18W halogen replacement, and I tried one.
It was very noticably dimmer than the 25W candles, so I went
to the next size up, 28W halogen. That's fine, so they've now
all been replaced with 28W halogens. So far, none of the
halogen replacements have died, and the increase in light
output has been welcomed.

2) Central light with 3 x BC 60W cables plus 2 x 60W wall lights.

In this case, I wanted to reduce power consumption, mindful of
the 300W of lighting, but the fittings/shades were very much
wanted, and so I had to think of some way which retained them.
I decided to convert them all to 12V halogens.

I made up five adaptors to convert BC to GY6.35 (bi-pin), so I
could retrofit 12V capsule lamps, being careful to make them so
filament position was the same as with the 60W candles.
http://www.cucumber.demon.co.uk/lights/adapter.jpg
I bought 35W 12V halogen capsules to replace the 60W mains lamps.

The dimmable electronic transformers are mounted in a vented
metal case in the room above (including additional self-resetting
termal trips), but this required some rewiring, which was
fortunately easily done as there's currently no floor covering
in the room above (which was the reason for doing this now).

Two further considerations. 12V lighting will draw 20 times
more current on the 12V side, so consideration needs to be given
to the current carry capacity of conductors. Secondly, I want to
be able to revert to mains lamps in the future without gaining
access under the floor again, so any new cabling used will still
be mains to allow reuse in the future.

The central light at 3 x 35W 12V will draw 8.75A which is within
the capabilities of 1mm T&E, so I did try using the existing
wiring, but with the expectation the voltage drop would be too
high for efficient 12V operation, and indeed it was. So I swapped
this for 2.5mm cable. What surprised me was this didn't make much
difference - I was still losing too much in the cable - much more
than I initially calculated, until I remembered the output is high
frequency, and the skin effect. Didn't have any 4mm cable, so went
straight to 6mm, and that worked fine, helped (from the skin effect
perspective) by being multi-conductor. The 1mm cable seemed to be
OK for the wall lights, one of which was directly below the
transformer, but I did change out a length of the other one for
2.5mm just to give a bit more headroom. I also rewired the central
light itself, using 2.5mm extra-flexible test meter singles from
the rose down to the point where it splits to each lampholder.

Anyway, this has been a stunning success. Unfortunately, I didn't
actually measure the light level in the room before starting, but
the 35W 12V halogen capsules produce noticably more light than
the 60W 240V candles had done (although the halogen capsules are
high efficiency type).

--
Andrew Gabriel
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