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Energy Savings for Lightings


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I am curious to know what is the technology behind energy saver for lightings?


I've seen quite a lot of these products in the market which are installed at DBs. For residential or office, the PF for fluorescent lights is about 0.85 which is considered relativety high. I heard that by installing these energy saver thing, the light will be dimmer, that's the "trade off" for the savings??? How true is this?


How about energy savings for industrial/factory lightings such as ballasts or discharge lamps? same technology as fluorescent lighting?



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Hello klangwcng


The devices that I have seen basically reduce the voltage applied to the lamp and reduce the power consumed. They save energy by reducing the output rather than improving efficiency. You can achieve the same result by fitting smaller lamps or turning some off.


Best regards,

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  • 4 months later...

A flourecent light fitting will give the same (or very similar) light output down to 60% of the rated voltage. At these lower voltages you will save energy (i.e. at the higher voltages the lamps/fittings are inefficient)


The problem is that you need the full rated voltage to strike or start the lamp. At 60% rated voltage the lamp will not start do this is why the "controllers" are used.


We have used them in our company and they work.

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Hello klangwcng


Reducing the voltage will reduce the light output, but may not necessarily improve the efficiency. If a region is overlit, then reducing the voltage will reduce the power consumption, but it will also alter the colour balance. You may be better off to reduce the number of lights that are turned on. You will gett lower power consumption and lower light levels but the colour balance will not be altered.


best regards,

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Is there any way of putting charts/graphs on this forum?


We have recently put some lighting controllers in a car park as a trial. To test the principle we reduced the voltage to the lighting circuits and measure the voltage, power (kW) and lux level at defined points.


The results showed that at lower voltages the fittings produced less light but consumed a disproportionate lower power (i.e. we got much more lux per kW).


From this we concluded that fluorescent lights are more efficient (conversion of electrical power to light) at lower voltages.


Putting in less fittings but still running them at a higher voltage would be less efficient.




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Hi Kevin


If the lamps are running above their design voltage, and they are using a non electronic ballast, then you can get excessive losses in the ballast. In this case, reducing the voltage will improve the efficiency.

Unfortunately, with tubes, the terminal voltage alters with age, so there is no one voltage that is optimum. Reducing the voltage may work for new tubes, but cause problems with older tubes.


Good Light fitting manufacturers design for high efficiency. You may achieve improvements early in the lamp life, or if the voltage is too high, but I would be reluctant to say that it will work in all cases.


Best regards

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