DIY Doctor

Dimmer Transformers Slowly Dying Across House

Postby mike_bike_kite » Wed Sep 25, 2019 12:53 pm

Our house is full of dimmer switches that are all steadily dying. I'm fairly certain it's the transformers that are going as we've replaced a few easy to get to ones and that fixed the issue. The ones that are left are now much more difficult to get to.

Is there an easy way of replacing the transformers (or just converting the lights to on/off switches) without pulling down the ceiling or pulling up the bathroom tiling etc?
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Postby ericmark » Wed Sep 25, 2019 8:24 pm

Seems some error in post, is it the dimmer switch or transformer, or electronic transformer which is failing?

With quartz lamps you should not dim them, it relies on the quartz envelope being very hot so tungsten will not adhere to the quartz so either over or under power will cause the bulb to fail, when they fail you can get ionisation inside the bulb seen as a bright flash which can overload electronic transformers and cause the cheaper one to fail, and electronic transformers are a lot more than simple transformer and the capacitors in them have a limited life, so will need replacing from time to time.

You can dim quartz, but life reduced if you do.

A proper transformer gives out AC at 50 Hz tend to last for many years but high or low input means high or low output and the inrush tend to mess up dimming switches.

Electronic often have a range of output 30 - 150 VA where non electronic will work zero to max rating, so non electronic work with LED lamps better, and electronic work with quartz lamps better.

There are some dimmer units that fit behind ceiling rose, often using a remote control, but most replace the switch so are easy to get to.

Lighting power supplies following the regulations need access for maintenance, however I have seen when when fitted there was access often floor boards marked "Transformer below" then some one latter has added some thing to stop access.

Be it the electrician, the carpet layer, tiler or other if they did not follow rules you would need to chase them, although unlikely to get much of a result.

12 volt extra low voltage lights were in the main made so the filament was thicker so they lasted longer, some times fitted in bathroom to comply with IET/BSi rules but else where no real need for extra low voltage once you move to LED, so today most lights are low voltage (230 volt AC) so no transformers or electronic transformers, some LED use a extra low voltage DC supply and some use a 50 Hz AC supply and one has to be very careful, much simpler to use 230 volt AC where permitted.

I am moving towards all LED, however there are some problems, if the dimmer uses a neutral often they will not work with UK wiring, and if it does not, often the LED's will flash, also they do not change colour when they dim so not the ambulance found with tungsten.
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