How to Avoid Voltage Drop with LED Lighting

Installation Advice

By its own definition constant voltage LED lighting requires a specific supply voltage that remains constant.

Typically constant voltage LED light fittings require either a 12VDC, or 24VDC power supply. Constant voltage LED drivers ensure that the supply voltage remains constant, despite any fluctuations in mains supply voltage.

MEAN WELL ELG-240 — MEAN WELL Constant Voltage LED Driver

However, installers of LED lighting need to be aware that running long lengths of DC cable from a LED driver to a LED light fitting can result in voltage drop, so that by the time the voltage reaches the LED light fitting it is lower than what is required for the LED lights to illuminate correctly.

In an ideal world you always want to do any long runs on the AC side, with the LED driver positioned as closely to the LED lights as possible.

Naturally, there will be some applications where this is just not possible and longer runs of DC cables are required.

If you find yourself in this situation then there are few steps you can take to avoid running into trouble.

First of all you need to calculate any voltage drop that you are likely to experience. There are some useful online calculators available, which make this job fairly quick and simple. You will need to know the gauge of the DC cable you will be using in order to make the calculations.

The following link will take you to an online voltage calculator:

http://www.calculator.net/voltage-drop-calculator.html

Once you know the actual voltage drop you can take the required remedial action. There are a number of options open to you.

Probably the most cost effective and simplest solution is to choose a LED driver that has an adjustable output voltage. This way you can adjust the voltage up to compensate for the voltage drop.

ADM stocks two series of MEAN WELL LED drivers that are available with an adjustment facility:

When ordering, ensure that the part # you request has an ‘A’, or 'AB' suffix this denotes the LED driver is adjustable.

The key difference between the ELG series and the HLG series is price and warranty periods.

The ELG series is the more cost effective of the two models, but has a shorter warranty period of 5 years. The MEAN WELL HLG series LED drivers have a 7 year warranty.

If you find that the adjustment range offered on the above LED drivers is not wide enough to allow you to deliver the required voltage, then you can use a MEAN WELL DC-DC converter to step the voltage back up.

ADM stocks a range of MEAN WELL DC to DC converters ranging from 15 Watts right through to 1000 Watts.

Constant Current LED Light Fittings

There are circumstances, where voltage drop can affect the operation of a constant current light fitting. The voltage may drop below the range required for the LEDs to illuminate. In other words, the current supplied may be correct but not enough power is present to drive the LED.

If you run into this problem, there is a low cost solution to rectify the problem.

You can use a MEAN WELL step-up DC to DC LED driver.