Light Hanging Guide: How high should my MLED-150s be?

Light Hanging Guide: How high should my MLED-150s be?

This is a short tutorial on recommended hanging distances for the GRT Horticulture MLED-150 LED lighting bars.


Introducing the GRT Horticulture MLED-150

The MLED-150 is an LED lighting bar made by GRT Horticulture, sporting Samsung's latest LM301H diodes in 3000k with additional 660nm red diodes for the best possible light spectrum to flower/fruit under, which it is designed for. The spectrum this light outputs has produced some of the best results we've seen, as the ratio of red to blue light is beautifully balanced for great flowering results. 

The MLED-150 is powered by a 150W MeanWell driver and comes with additional power extension cables to allow the user the choice of mounting their driver either onto the fixture or away from the light itself for easy power supply management.

The MLED-150 is part of a Modular LED lighting bar system, designed specifically for use with additional MLEDs or other lights for the user to have the greatest flexibility in how they decide to setup their grow room. The concept of the MLED series is to allow users to setup their grow room with the exact amount of light spread evenly throughout their room by assessing their requirements to determine the amount of MLED lighting bars and their spacing they would need to saturate their grow room with light. This is one of the biggest draws of the MLED's design that we love over the standard fixed one-piece system that cannot be adjusted.


MLED hanging height

Hanging recommendations for the MLED-150

One of the greatest things about the MLED-150 is its spread of light. The MLED outputs a respectable quantity of light in a 4 foot long, roughly 1 foot wide projection, with the adjacent foot being roughly 50% the output of the foot wide spread directly under the light. The allows users to place an additional MLED 2 feet apart from another MLED to achieve a consistent light spread by overlapping the 50% intensity light output from the adjacent MLED, resulting in 2 MLED's achieving a consistently balanced output over 4x3' space for vegetive growth.

The light intensity of the MLED can be increased by reducing the hanging height to the canopy or by using additional MLEDs to increase the overall quantity of light, relative to your plants needs.

One of the major draws of using LED lights with a large diode spread is the lower light intensity in a single spot, reducing the chance of light stressing your plant and allowing the user to get their light much closer to the plant without stress, while still having the ability to produce intense light when combine with additional MLEDs. This has been a drawback of some of the intense 'quantum board' style LED lights that some users experience when incorrectly distancing their light from their canopy, resulting in major plant stresses.

The MLEDs have the modularity to allow the user to hang each MLED at difference heights or angles for a desired spread or intensity of light.


Hanging Height Recommendations: Per single MLED-150

Vegetive Growth: 40-60cm distance from canopy (460-290~ PPFD directly under light)

Flowering Growth: 15-30cm distance from canopy (850-560~ PPFD directly under light)


PPFD Readings directly under a single MLED-150:

  • @ 15cm - 850 PPFD
  • @ 20cm - 750 PPFD
  • @ 30cm - 560 PPFD
  • @ 40cm - 460 PPFD
  • @ 50cm - 340 PPFD
  • @ 60cm - 290 PPFD


Light Saturating your room with MLEDs

For this example, we're going to use the most commonly sized grow room space of 1.2m/sq (or roughly 4x4) as our room size.

To saturate a 1.2m/sq space with light for flowering, you will need 4 x MLED-150s, evenly spaced for perfect wall to wall light levels across your canopy.

With 4 x MLED-150s in this space, you will have roughly 800-850~ PPFD @ 20cm distance from canopy, wall to wall, corner to corner. This number is the safe quantity of light that most fruiting/flowering plant varieties can handle before stress responses start when giving 12h of consistent light.

When using this setup for basic vegetive growth, it is recommended to hang your MLED between 40-50cm from canopy for a rough 460-340 PPFD even spread, wall to wall.

For late vegetive growth you can reduce the hanging height to 30-40cm for faster growth.



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