Industrial Climate

Climate management in a grow room

Dehumidification, humidification and cooling are sized together, from a water load expressed in litres per day and a heat load expressed in kilowatts. Never from a floor area.

The water balance governs dehumidification

A crop returns through transpiration almost all of what irrigation supplies: 1 to 5 litres per square metre per day depending on species, growth stage and the radiation received. It is that quantity of water to be removed from the air each day that determines the capacity to install, not a covered area printed on a data sheet. On an existing installation, an irrigation reading and a drainage reading are enough to establish it.

Heat balance: three items working against each other

On the heat side, almost all the electrical power installed in lighting reappears as heat in the room, to which motors, people and, under glass, solar gains are added. The two balances are not independent:

• a refrigerant dehumidifier heats the air it treats: it returns the condenser heat and the compressor work;
• an air conditioner dehumidifies for as long as it is cooling, then stops as soon as the temperature setpoint is reached, at the precise moment when relative humidity continues to rise;
• adiabatic humidification cools: evaporating 7 litres of water per hour absorbs in the order of 4.5 to 5 kW from the room air.

A control system that drives these items separately makes them cancel each other out. Humidification and dehumidification must be interlocked against one another, with a sufficient dead band, and setpoints are better expressed as vapour pressure deficit than as relative humidity alone.

Humidifying without contaminating

The only appliance attached to this level in its own right is a 7 L/h ultrasonic humidifier with replaceable ceramic membranes. An ultrasonic mister atomises water with everything it contains: limescale, dissolved salts, micro-organisms. Reverse osmosis water is not a refinement here but a condition of operation — without it, white deposit on foliage and scaled-up membranes. Tank maintenance is a hygiene matter: aerosolising stagnant water in an occupied room creates a health risk.

What is decided on the plan, not on delivery

• Redundancy: two machines of half the capacity rather than one, so that a single failure does not cost a room its climate.
• Condensate: gravity drainage wherever the fall allows, a lift pump otherwise, with an accessible inspection point.
• Running cost: litres per kilowatt-hour on the dehumidification side, EER on the cooling side, on machines that run all year.

The equipment actually available in this branch is in industrial dehumidification. Air exchange, the third lever of climate, is calculated with our technical team from the installed lighting power and the temperature rise accepted. For non-professional use, the climate management section covers everyday needs. This section forms part of our professional range.