How high should you hang an HLG light and set its power?

The right hanging height for an HLG light depends on the exact fixture, its dimmer setting, the crop area and growth stage. Start with that model's manual. Adjust height and power gradually while checking PPFD at canopy level. A distance copied from another lamp can create a bright centre and weak edges.

Plan the space before hanging the fixture

Measure fixture dimensions, approved mounting points and the clearance above plants at their expected final height. Allow for hangers, airflow and access. Follow the manual supplied with the unit for its mounting and electrical requirements. US HLG pages may describe different plugs or controllers from the European item; do not transfer those details without checking. A qualified person should assess any electrical work outside your competence.

Height and dimmer work together

Moving a fixture closer often increases intensity below it but may reduce uniformity. Raising it can spread the light while reducing PPFD. The relationship differs between a compact panel, the elongated 350 Diablo and the broader 750 Diablo. Dimming changes emitted light; it cannot by itself fix poor geometry.

Choose an initial position within the exact manual's limits, set power conservatively and measure a grid over the real crop area. Include centre, corners and edges. If the mean is suitable but the centre is too high and the edges too low, reconsider mounting position before adding power.

A repeatable adjustment routine

1. Record model, manual, height, dimmer setting and cultivated area.
2. Measure PPFD at canopy level using the same grid each time.
3. Compare the readings with documented needs for the species, stage and photoperiod.
4. Change one setting at a time, then measure again and observe crop and climate.
5. Repeat when plants grow, tables move or neighbouring fixtures overlap.

A phone app may be a rough aid, but its spectral response and calibration must be known before using it for quantitative decisions. Prefer a suitable quantum sensor for measured PPFD.

Avoid common mistakes

Do not set height using only a centre reading, copy another model's distance, mistake a dimmer percentage for measured watts or forget how tall the crop will become. There is no universal PPFD setting for every species and stage. The 250 Veg Pro is another format to study for vegetative areas, always with its own manual.

Further reading : understand PPF, PPFD and DLI · read a PPFD map.

Common questions

Should the dimmer start at full power?

Full power is not a universal starting point. Check received intensity and distribution, then increase gradually if the crop requires it.

When should PPFD be measured again?

After changing height, output, layout or canopy level. The installation determines the interval.