Why do my Council LED streetlights keeps failing?

LED Street lights lined going down a road
Installation Advice

Are you finding yourself constantly being called out to LED streetlamps that have failed? You may have tried replacing both the LED luminaire and its power source, only for the streetlamp to fail again?

In this article, we explore common issues with failing LED streetlights with a handful of possible solutions to help guide you.  

constant current LEDs connected in parallel

 

Issue One: LED luminaires powered by a Constant Current LED Driver have their leds connected in parallel. 

Constant current LED Drivers are used to power LEDs that have no internal current regulation. When you connect multiple LEDs to a constant current LED Driver in parallel, you run the risk of greatly reducing the life span of your LEDs.   

Why is this a problem? Not All LEDs are made equal. 

It is important to understand that all LEDs have a manufacturing tolerance. This means that even though you are using several LEDs with exactly the same part number, there can be slight variances in the voltage at which the LEDs startup.  

How can this effect my LED street Lights? 

Let’s say you have a constant current LED driver with a 1A output powering 5 LEDs with an input current rating of 200mA.  

Due to the permissible manufacturing tolerance, one of the LEDs may come on once the output voltage of the LED driver reaches, say, 9V, another may come on at 9.3V, and the others at 9.5V, 9.6V and 9.7V.  

Because the first LED is on before the others it will draw a slightly higher current than it needs. The other LEDs will be slightly underpowered. As the first LED is being overdriven, it is quite likely that its lifespan will be reduced, and it could fail prematurely.  

This failure has a knock-on effect. Because there are now only four LEDs connected to the LED driver, they will all be driven with a current of 250mA. This means all 4 LEDs are now being overdriven. This will most likely result in another of the LEDs failing soon. Of course, this then means the remaining 3 LEDs are now driven with 333mA, which means it won’t be long before they too fail.  

solution: adjust the current down on your constant current led driver 

It is preferable for multiple LEDs to be connected to a constant current LED driver in series. This way should one of the LEDs fail then power is cut to the remaining LEDs, protecting them from being overdriven.  

If the LEDs have been connected to a constant current LED driver in parallel, then there is something you can do to protect your LEDs from being overdriven.  

We suggest adjusting the current output down on the LED driver. This should ensure that none of the LEDs is being overdriven, preventing the daisy chain of failures mentioned above from occurring. The downside of course is that the lumens output of the LED lights will be lower than expected. However, in many cases this may not be noticeable to the eye.

If the existing LED driver is not adjustable, ADM may be able to identify a suitable replacement that is adjustable, for example, the MEAN WELL HLG-320H-24A-AUP.

A MEANWELL power supply, the HLG-320H-24A looks very similar to the HLG-320H-12, but includes a small access port on the front to adjust output.
An HLG-320H-24A LED driver looks very similar to the HLG-320H-12, however includes an adjustable pot feature on the front. 

 

issue 2: Is Your Power Supply Overheating?  

Often when replacing a power supply for an LED streetlight, the replacement might not be the same dimensions as the original PSU and require an electrician to jury rig a new installation location. Sometimes, these new locations can be ill-thought-out, with PSUs being left exposed to direct sunlight. 

A Solution: Consider installing your LED Driver away from external heat sources.   

Be aware that power supply units are still subjected to environmental factors such as the heat from sunlight. This can cause the temperature inside the LED driver to soar past its maximum temperature rating. Put simply, a power supply unit shouldn’t be jury-rigged to power from the top of the streetlight and cook in the sun all day. This may cause a premature failure that will not be covered by the manufacturers warranty. Never mount a LED driver in direct sunlight, even if it is IP67 rated.

Still having issues? 

If you have any questions about connecting LEDs to LED drivers, please do not hesitate to call ADM on 1300 236 467. A member of our expert team will gladly answer any questions that you may have.  

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11 July 2023