GU10 downlighter fittings with CFL lamps

Dippy · 24 Nov 2007

I see that 7W CFL GU10 lamps are 58 mm long, and GU10 halogens are between 50 and 58 mm long. Can I assume that the CFL lamp will fit into any GU10 downlighter fitting even thought it it advertised as a 'halogen' fitting?

Also, since the 11W CFL GU10 lamps are around 75 mm long does this mean that they won't fit a standard fitting or that they will just protrude about 15 mm? Are there any downlighter fittings that are sized especially for the 11W CFLs?

RF Lighting · 24 Nov 2007

CFLs should fit any standard downlighter.

They will stick out from a fire rated DL, but will still be safe to use.

You can buy fire rated DLs which are designedth CFLs

Steve · 25 Nov 2007

RF Lighting said:
CFLs should fit any standard downlighter.

They will stick out from a fire rated DL, but will still be safe to use.

You can buy fire rated DLs which are designedth CFLs

7 watt CFLs will fit any GU10 fitting.

9 and 11 watt CFLs will ONLY fit fittings with a loose lampholder cap on a wire. They will NOT fit fittings with a fixed lampholder cap on a metal bridge.

I should add, all CFLs will fit in any fitting, as they are the same diameter, but they will stick out by 2 centimetres in fittings with a fixed lampholder!

See here.

Dippy · 26 Nov 2007

Thanks for the answers. One more question, this time on brightness. I have one CFL (standard ES fitting) and it is 7W. IMO the brightness is significantly less than a 40W incendescent lamp. I have read that a 9W will be about as bright as a 40W incendescent and a 11W CFL about as bright as a 60W lamp. Is this really true?

Steve · 26 Nov 2007

Dippy, the thing you must understand first is that a GU10 halogen lamp creates a focused beam of light. All of its light is directed one way into a circle. This creates dark and light spots in the room.

A CFL has a reflector, but because the light source isn't a point (filament), but rather the whole lamp is the light source, the reflector causes the light to be spread much more evenly. A single CFL will provide dim light for an entire room, whereas a single halogen will provide light for a 3 foot circle directly below it and cast the rest of the room into the shade!!

Also the colour of light affects the "brightness". A halogen lamp produces light towards the orange end of the spectrum, whereas a CFL produces light more in the blue / midrange region.

I find a 9 watt CFL is a more than adequate replacement for a 50 watt halogen.

Dippy · 27 Nov 2007

Thanks. Yes I appreciate what you are saying. My plan is to have downlighters to cover the entire room, but use a combination of energy-efficient (relatively speaking) halogens and CFL downlighters. This is so that I can have the low level dimming capability of halogens but when I want a bright setting I am not relying on halogens at full power, rather a combination of CFL downlighters and halogens. I am currently planning a ratio of about 2:1 halogen DLs to CFL DLs in most rooms.

I plan to buy some kit and try it out for myself before committing, however there's a lot of kit to choose from and so I want to try to narrow my requirements.

Dippy · 28 Nov 2007

Thanks! Unfortunately the Megaman dimmable won't work the the lighting control system I intend to use.

Paul Barker · 28 Nov 2007

I get an Aurora brushed stainless lamp holder (but fixed, no gimbal) from Edmundsons and fit megaman 11 watt cfl's into it which have a warm white colour.

However for brightness I prefer 12 halogens. depends what your priorities are. I don't find cfl's bright enough for old folk.

Robin28870 · 28 Nov 2007

Dippy said:
Thanks! Unfortunately the Megaman dimmable won't work the the lighting control system I intend to use.

Is that old Megaman "5 step dimming GU10's" or their new "smooth dimming GU10's" ?

or both?

Dippy · 29 Nov 2007

I don't know which, but looking at the DorS system they advertise it appears that in order to get the required level of dimming it is necessary to apply full power then remove it and reapply it within a specific time period. Actually I think the system I am planning (FlexiDim) can do this, but I think it'll be complicated to program and end up looking wierd when operated. So I'll stick to my plan of mixing normal CFL DLs with dimmed halogen DLs.

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GU10 downlighter fittings with CFL lamps

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