13 feb 2019

Light remnant

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Light remnant is one of the main headaches connected to the use of LED luminaires

Light remnant is one of the main headaches connected to the use of LED luminaires when light is “switched off”. That is why JISO ILUMINACIÓN has decided to write about this issue.

LED technology, although apparently similar to traditional lighting, has differences which must be taken into account for their normal functioning:

General recommendations:

1- Firstly, follow the installation and connection order for the different elements:

  • Perform line checks, the neutral without direct current to DRIVER/LUMINARY and the phases to switch elements.
  • Connection order: connect the LED luminary to your DRIVER, then connect the Driver to the Line and finally introduce the current.

2- Each DRIVER with the appropriate LED luminary!

The power supplies (DRIVERS) are electronic devices and not merely transformers. They deliver regulated voltages and currents and have direct current outputs, so respect connections and polarities.

CAUTION especially in installations which feature different LED luminary models. Check the driver, the type of current, the voltage and the polarity, taking into account that the current can be 300mA, 350mA, 600mA, 700mA, 1000mA, etc., and that the output current of the driver is continuous.

3- Wiring. Splices and Connections.

It is important to use suitable section wiring, considering that the current required is very small. The splices require welding and insulation with heat shrink tubing or tape. Observe the connections, whether they are series or in parallel according to the manufacturer’s installation recommendations.

4- It may be that the LED luminary is giving off any light but always remember that current is still circulating in the system.

If you encounter any issue, please give us the opportunity to resolve it before returning the product. Most technical assistance questions can be answered through our knowledge base on the website: www. jisoiluminacion.com, or via the technical support service by email: asistenciatecnica@jisoiluminacion.com. The use of the electronic elements and parts of the installations can cause some very specific and sporadic incidents which do not damage the LEDs but which are striking, such as residual luminescence (brightness), flickering or switching off shortly after installation (temporary block which works by removing and returning the switch).

All these effects existed previously but were not detected because lighting technologies were not as efficient; a lot of energy was needed for their operation and the “residual” voltages, the induction generated voltages, the commuted point installations and the mechanisms with light signal did not affect them.

Most frequent causes of the effects mentioned above:

1- The switches of the electrical installation cut the neutral whereby the phase reaches the LED.

2- Current flows through the neutral, due to earthing shunt or other causes.

3- Induced current. This can be generated by the presence of large household appliances or industrial  achinery.

4- Pilot signalling switches (Neon or LED). This type of switch admits a current of 12 to 30 volts.

5- In switched-point installations, a residual voltage may be produced (due to the length of the crossing lines) which acts as a capacitor generating small voltages which can maintain some brightness, flickering or blocking of the LED luminary driver.

6- The installation has two active poles so there is always potential in one pole of the driver.

7- The ceiling where the luminaire is placed has electrical conductivity and, as a result, the contact between the ceiling and the luminaire body thanks to the existence of an active pole connected, makes possible to have potential and remaining light.

Possible solutions:

In points 1, 2 and 5, we recommend checking the electrical installation.

Neutral direct to Driver – Phase to switch


Image 1. LED luminary connection diagram + switch

To easily check if it is neutral or phase, we can use a pole detector, or Multimeter/Tester.

- When you touch the phase conductor with a pole detector, the neon light shines. In the new models with a LCD display showing the voltage, when you touch the phase it will read 220V.









- In pole detectors, neither the neutral nor the earth triggers the neon light. And in the pole detectors with a LCD display, no voltage is indicated for the neutral or earth.









With the Multimeter or tester using Voltmeter AC 750V function

Between phases – neutral 220V-240V will be indicated.


 Between neutral and earth 0V.


And between phase-earth 220V-240V.















Another possible solution in cases of residual current would be to install a capacitor of 0.47uF 400V (Solution points 3 and 4).

Image 2. Condenser REF. DCCONDEN-1

You can also use bipolar switches or contactors to count the current flow to the lighting lines. (Solution points 3 and 4.



This last mechanism would allow, in any case, to eliminate the remnant of light so, when the power in the driver is removed, the driver could not be put in tension in any case.

Technical Deparment

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