Qs re MR16 & GU10 downlighters

Feb 11, 2014 3 Replies

Trying to understand modern downlighters(!)



Typically these push into a c.80mm dia hole cut in the ceiling plasterboard .



There seem to be 2 distinct styles:



A. 12V based on MR16 bulbs usually wired via a separate transformer.



B. 240V based on GU10 bulbs usually wired direct into the mains.



Bulbs may be halogen, LED or CFL.


Q1: How do GU10 LED (240v) (eg screwfix 24524) replacement bulb units work? Inherently, all LEDs are low voltage devices (typically 2V to 4V). Where does the other 236V (ie 240V-4v) disappear to?



(guessing some: sort of electronic voltage dropper as in CFLs - if so, how much heat does that produce? Is it an interference source?)



Q2: MR16 bulbs are also described as . Does GU5.3 mean the same as MR16?



Q3: Screwfix list 2 types of tranformer for MR16 (jan catalog p255) cat no 66599 (LED constant current driver) & cat no 85503 (LED constant voltage d river). Which to you use & when?



Q4: How much heat is lost in these transformers?



Q5: Is there a program out there which can be used to design a multi-unit c eiling installation to provide a reasonably even illumination of a worktop h (eg 900mm) off the floor from a ceiling (say) H (eg 2700mm) high? (assumi ng everything is horizontal & non-reflective).



TIA for any & all help.


They have a power supply built in, like CFL's do.

Very little power is wasted by the PSU.

No. It means 5.3mm between pins. Other types of halogen also use 5.3mm pins.

MR16 LED retrofits are 12V constant voltage.

Very little.

That's the task of a lighting designer! Look for a lumen to lux calculator, but in practice, it's more complicated than just that. You will probably want to mock up some fittings and test with a light meter.

DerbyBorn wrote in news:XnsA2D3926C4B59BTrainJPlantntlworldc@81.171.92.236:

D: CFL

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