by ericmark »
Tue Aug 23, 2022 10:37 am
There are two types of 12 volt transformers, the toroidal lighting transformer will work from zero to rated output, and has same frequency output to input, and you can fit LED AC G5.3 lamps to replace the quartz halogen lamps without any alteration.
The electronic lighting transformer regulates the output, with is normally in the kHz range, and often there is a minimum as well as maximum output, and since a LED is a diode it can become a transmitter, it seems common to use a DC power supply often called a driver to run LED 12 volt units, some so called electronic transformers, which would be better labelled as switched more power supplies will go from zero to maximum output, so need to read the label.
The main problem with changing from extra low voltage (12 volt) to low voltage (230 volt) is since 1966 the regulations require an earth wire to be take to any fixed installation with the exception of a light suspended from the ceiling, and the MR16 lamps are not suspended so require an earth taking to them, even if not used.
I think main ignore that, but it would be wrong not to point it out, as could result in a code C2 with an EICR.
Personally I would change to GU10, note a GU10 refers to the connection, the old 12 volt was G5.3, the MR16 refers to a spot light with a multifaceted reflector 16/8th of an inch across, so a quartz halogen GU10 is still a MR16 lamp, and in the main LED lamps both 12 and 230 volt are not MR16 lamps as they don't have the reflector.
Like calling the vehicle test a MOT when the ministry of transport went years ago we still use old names.
Main difference between 12 and 230 volt is you can get smart bulbs with 230 volt that can dim and colour change both colour temperature and red, blue, green.
In the main 12 volt use a resistor as a driver, each LED is approx 3 volt, so 3 LED's and a resistor is used to make 12 volt, the resistor produced heat, so it is hard to do this and comply with new part L law, New fittings must produce 82 lumens of light per circuit watt for general lighting or 75 lumens of light per circuit watt when used for accent or display lighting. It was 45 lumen per watt, so many MR16 bulbs now fall foul of the new regulations, the 12 volt DC MR16 bulb can be up to 100 lumen per watt, narrow boats and caravans need to use as little power as possible, often they have a voltage range of 10 - 30 volt, but the domestic lamp often marked 50 Hz used in most homes, is down to 75 lumen per watt. Not even as good as the old fluorescent lamp.
With a GU10 lamp the cheap lamp uses a capacitor as a current limiter (driver) which does not produce much heat, with the G5.3 normally it uses a resistor, so the question is how long will we still be able to buy cheap bulbs.
The DC version uses a micro chip to control the current, which makes the lamp more expensive, the 230 volt smart bulb also uses a load of electronics so we are likely to see less of a difference between price of a smart bulb and normal bulb.
