Tag Archives: control systems

LED has a bad case of Gremlin

Gremlin-LED
LED technology offers huge promise but we shouldn’t be blinded by its potential. In service to my customers I have to remain vigilant on LED’s shortcomings. In this instance a flaw has appeared which requires the attention of all those currently specifying LED lighting installations which use control systems.


It would seem reasonable to assume that LEDs draw less power from a circuit. After all down-lights and strips require a fraction of the wattage needed by conventional tungsten halogen lamps. For instance, if you take a typical restaurant, you may have a 5 amp lighting circuit that delivers 1150w. Using older technology halogen lights you would be comfortable deploying about 20 units across the same circuit. Surely, given that LED lights relatively ‘sip’ power of at least 80% less compared to their – you are permitted to assume that you can pepper the ceiling with downlights wherever you fancy? But you could be making a costly mistake.
The simple fact is that making this once safe calculation on capacity is no longer valid! It is likely that when the lights are switched on that they will flicker or will fail leading to a total revision of the lighting design – pulling the assets and refitting. It is the designers worst nightmare and it is happening all the time.
Why?
In truth we receive conflicting information from lamp, driver or luminaire manufacturer’s and even the makers of control systems aren’t 100% sure yet how many lamps or luminaires will work without testing. In electrical terms it is due to the capacitance of the LEDs that leads to this need to de-rate a circuit. After some investigation it seems that a power spike is commonly caused across the dimmer channel which requires a 90% reserve in capacity. So when controlling with a digital dimming system, effectively the power saving that is delivered by LED lights is thrown away in wasted unused capacity in the expensive dimmer channel.
To remain safe, controls suppliers are issuing a blanket de-rating of 90% – so only 10% of the channel can be used regardless of whether LED lamps or luminaires are being used – where there is some evidence that it’s only relevant LED lamps and not luminaires with their own drivers.
How to avoid the problem?
The prospect of decommissioning and re-commissioning a lighting installation is a nightmare for designers and clients alike. How do you avoid the mistake in this modern age where dimming and control systems are widely demanded?
The simply truth is that with no definitive advice available from suppliers you have to test the load as a practical simulation. At Orange Lighting we have quite literally constructed a circuit in our offices to test the control system and the LED lamps or fittings before we can design the system / lighting circuits. After we are sure that one dimmer channel on a rack is functioning we are confident to roll out the complete system.
We are happy to share this knowledge too. If you have a project that needs a combination of LED and control with dimming – call us and we will be happy to offer a solution.