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Calculated an installation precisely, only to find the circuit overloads as soon as it’s switched on? We take a look at inrush current and power factor, the hidden LED disruptors.

It’s a contentious subject, but independent testing has found a huge disparity between the wattage listed on an LED’s box and the power it actually consumes. Inrush current and power factor both have an impact on the performance of an LED and, as such, the dimming quality when paired with control devices. Yet so few installers are aware of just how much they can affect the load they are trying to dim.

Inrush current

Inrush is the spike in current that is being drawn by the LED power supply. It mainly occurs when it is first switched on, but also happens during the mains cycle as the reservoir capacitor requires a charge. The two important numbers here are:

-          how big is the spike? (measured in Amps)

-          how long does it last? ( the duration measured in time typically in micro seconds)

Needless to say, the bigger the spike or the longer the duration, the more it will affect your LED installation, increasing the load and potentially changing the dimmer you need to install.

Inrush on the job...

A contractor was recently having issues dimming 100W load made up of ten 10W round panel downlighters with our ZGRIDLED+. Our ZGRIDLED+ can control up to 250VA/Watts, so could easily support a 100W load – yet this installation was not working as it should.

Yet the contractor found he even had to change the circuit breaker to a Type C, as the Type B he had installed had been ‘tripping out’

We tested the lamps in our lab, and found that each LED was generating a 30 Amp spike: in total, we saw well over 100A for 5mS.

It’s little wonder this would not work, and highlights how important the inrush data is and why it should be published on the box.

Power Factor

In simple terms, power factor is a measure of how efficiently the load current is being converted into usable output – ie, light.

In technical terms, it is the ratio between the kW (Kilo Watts) and the KVA (Kilo, Volt, Ampers) drawn by a load, where the kW is the actual load power and the KVA is the apparent load power.

Power factor is a good indicator of how efficient an LED power supply is, with unity power factor or 1 being the most efficient.

What does this mean for me?

When calculating the total LED load, simply taking the wattage written on the packaging and ignoring other factors can lead to real problems, especially when selecting the right dimmer to use. Inrush current and power factor really do play a significant part in the overall performance of LED.

If you have upcoming projects and would like us to test the lamp/fittings to ensure correct compatibility, please do contact us and save the headache of a wasted journey back to site.

For more information on how we can help you find the right selection of dimmers for your project, take a look at our project specifying article here [add link].


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