Most indoor gardeners sooner or later wonder what to consider when spacing plant lights properly. In this post, we explain how to hang Grow LEDs, what the consequences of improper hanging height are, and lastly, we show how to determine the correct spacing.
General rules for the suspension of LED Grow Lamps
How to hang plant lamps ?
For most applications, the common rope ratchets with carabiners have proven themselves. The LED setup can be adjusted in a few simple steps using the ratchets. In this way, the gardener remains flexible and can regulate the lamp height over the entire growth and life cycle of the plants.
The typical "Grow Hanger" or "Rope Ratchets" made of nylon fabric are ok and can carry large loads. However, you should make sure to choose a product with metal carabiners, in the cheapest offers you will usually find simple plastic hooks. Also the locking of the pulley can differ significantly in quality.
Professional tip: We have included a valuable alternative in our shop: Fyto Hanger are made entirely of steel cables and have a simple but reliable locking mechanism, which is also made entirely of metal.
Typical errors in the spacing of plant lamps
Plants can grow under a wide range of lighting conditions. Normally a few centimetres more or less distance does not make a big difference, but because you can control all environmental parameters in indoor growing, you should also try to get the optimum out of it.
Let's start with things you should avoid at all costs:
Hanging the Grow Light too High
In the past, when dimmable plant lamps were still rare, the distance between the lamps was used to regulate the intensity of photosynthetically active radiation (PAR) on the cultivated area. The further away the lamp, the lower the PPFD values under the lamp. This is partly because the light cone spreads out further, and partly because of reflection losses (or scattering losses if the growing space is not closed). This method of "dimming" is therefore not recommended because valuable energy is wasted.
The negative effect for plants when placed too high, is related to the intensity. They can show an exorbitant growth in length, called "vergeilen", which is noticeable by a strong increase in the distance between the nodes. Plants are genetically predisposed to outgrow neighbouring plants if there is insufficient sunlight.
Advantages and disadvantages of remote placement
- Possibly lack of intensity, horniness and low biomass build-up
- higher power consumption
- homogeneous illumination
Hanging too Close to the Canopy
With the traditional gas discharge lamps a big problem: If the NDL is placed too close, the radiated heat causes massive transpiration. The plants notice this immediately, they get burns. With LEDs this problem is significantly reduced, but can still occur. We recommend to keep a minimum distance of 10- 15 cm where possible. Otherwise a cover in front of the lamp is recommended. This can reduce increased heat radiation on the plants and also prevent the LEDs from being affected by leaves "growing into" them. In extreme cases, damage to the components could otherwise occur.
Too short a distance also means that the light cone can spread less. This means uneven PPFD values and a poorly distributed spectrum if different LEDs are used. If it is foreseeable that there will be little space above, we therefore prefer lamps with many LED chips. These can be distributed over the entire surface area and can be supplied with a very low current. This increases the efficiency, so that fewer losses occur as heat as well as the heat radiation per LED chip.
Advantages and disadvantages of close placement
- frequently increased evaporation (VPD problems)
- possible problems with burns
- potentially the best energy yield
What is the Ideal Hanging Height for Grow LEDs?
The ideal distance therefore also depends on the specific application and the lamp used. In particular, the radiation characteristic, i.e. the light cone, plays a role.
For applications where large areas are illuminated and there is a lot of upward space, lamps with secondary optics and a narrower beam angle can be used, suspended or mounted at a great height. Here reflection losses are much less of an issue and factors such as an ergonomic working environment and ease of handling need to be considered.
When growing indoors, two resources in particular are limited: Space and energy. Therefore, one tends to hang the lamps closer. This can save valuable space. Ideally, LEDs with a beam pattern of 120° and no secondary optics are used to eliminate all possible efficiency losses.
To ultimately determine the optimal distance from the plant lamp to the canopy, we need to analyze the lamp in more detail. PAR maps, which precisely map the distribution of the PPFD values, are suitable for this.
A FLUXshield Gold with 150 W. Can still very homogeneously illuminate an area of 60 x 60 cm at a distance of only 20 cm. Hardly any losses: 2.41 µmol/m²/J!
At a distance of 60 cm, the shield can only bring 640 µmol/m² onto the cultivated area. The efficacy is significantly worse at just under 1.5 µmol/m²/y.
The Triple Bar - 6 FLUXengines with 240 W. The target area is 80 x 80 cm. This lamp ideally hangs at about 30 cm above the canopy...
.... while at even shorter distances (20 cm) distinct hotspots above 1000 µmol/m²s are formed.
We carry out numerous PPFD measurements to obtain a solid data basis for the optimal productive use of plant lighting. Our findings are continuously incorporated into product development and provide users with a reference point for their own optimisations. The latest test results are published in the PAR database listed.