broadgage:

. . .

The light output of the halogen floodlights tends to be exaggerated also, but not as badly. It is common practice to take the LAMP output without any allowance for losses in the cheaply made reflector and cover glass.

. . .

I think Broadgage has a good point here. 5 to 6 thousand lumens sounds about right for the actual 300 W halogen lamp. In the fitting a sizeable portion of this light will need to be reflected and the efficiency of the reflective material comes into consideration, so the actual lumens emitted by the fitting will be rather less. Whereas light emitting diodes are intrinsically directional, and the figures quoted probably refer to the entire fitting.

Andy C:

perspicacious:


I don't know how much a halogen lamp output deteriorates with life.

 

In some cases 100% every five minutes! ?

I've been replacing fluorescent lamps with LEDs in several buildings. Going on manufacturers so-called lumen figures I'm either going to be suffering from burnt retinas or groping around in the half light! In practice I've just gone ahead and swapped them over and generally been satisfied. For example we've recently changed a community hall over from 14 70W twin HF fluoros to 14 single 6ft 4000k LEDs. On paper the fluoros should be about 13k lumens total per fitting, the LEDs about 7k so I'd be thinking the light levels will be reduced. In practice the lighting levels in the hall appear to be the same. I did consider going for cooler temp LEDs such as 3000k to replicate the fluoro lighting but 4000k seems perfectly okay without the blueness you get with higher temps.

. . .

In my experience, LEDs on places like instrument panels do lose light output over a considerable number of years, and it is beginning to look the same for the high power ones.


The directional properties of the lamps come into consideration here. Most fluorescent tubes emit light equally upwards and downwards. (Directional ones have been made but never came into wide use.) A lot of the upward light will probably be lost, especially if fittings are not kept clean (and by my observations places like community halls do not attend well to such matters). Whereas LEDs tend to direct light downwards where it is wanted by design.


I personally do tend to take "equivalents" with a pinch of salt, and would always look to lumen output. As has been said elsewhere, illumination is measured in lux, but it would be impracticable for a lamp manufacture to attempt to quote this, because it depends on distance of lamp from surface and many other factors such as size of room, reflectivity of walls, efficiency of light fitting, etc.


4 000 K seems to be settling down as a popular value for places like community halls and similar meeting places, avoiding the yellow of tungsten light but not as "blue" as the 6 500 K "daylight" types, which some may see as "less cosy".

AJJewsbury:

hertzal123:

hertzal123:

Thanks for all the replies,I may go with the 40W or 50W leds.

                                                                                Regards,Hz

Just noticed the Luceco 38W led flood has a power factor of 0.5,so not as cheap to run as they appear.

                                                                                                                                             Hz

Poor PF usually won't make much difference to running costs as normal metering records kWh rather than kVAh (except perhaps for some industrial situations where there might be a penalty for poor PF).

    - Andy.

It is the current that is the critical point where power factor is low. This is a concern on large, industrial systems, because the current supplied to a factory is larger than the consumed power suggests. The supply network must supply this current even though the charge is for energy used. Hence there may be a penalty for low power factor. For similar reasons, large-user tariffs may also charge extra according to maximum demand.


So how do LED spots replacing halogen figure in this? Let's do some quick maths.


The current consumed by a 300 W halogen floodlight at unity power factor, 230 V is 300/230 = 1·30 A.


The current consumed by a 38 W LED floodlight at 0·5 power factor, is 38/(230 * 0·5) = 0·33 A.


I wouldn't worry about the power factor if I were you.

hertzal123:

hertzal123:

Thanks for all the replies,I may go with the 40W or 50W leds.

                                                                                Regards,Hz

Just noticed the Luceco 38W led flood has a power factor of 0.5,so not as cheap to run as they appear.

                                                                                                                                             Hz