Grow Room Environmental Controller Guide
Grow Room Environmental Controller Guide
A grow-room environmental controller cannot create cooling, airflow or dehumidification capacity that the equipment does not already have. Its job is to measure the room, coordinate compatible equipment and use that available capacity intelligently.
This guide explains temperature and humidity triggers, VPD, minimum and maximum fan levels, dynamic transitions, buffers, sensor placement, active intake and exhaust balancing, alarms, remote monitoring and commissioning.
The correct sequence is:
What Does a Grow Room Environmental Controller Do?
A controller combines one or more environmental sensors with programmable outputs.
Depending on the equipment and controller, it can operate:
- inline exhaust fans;
- active intake fans;
- circulation fans;
- humidifiers;
- dehumidifiers;
- heaters;
- grow lights;
- and compatible outlet-powered equipment.
This is a feedback-control loop.
A Controller Cannot Create Capacity
Suppose a room requires approximately:
but the installed fan and duct system can only deliver:
Setting the controller to maximum cannot produce the missing 200 m³/h.
Likewise:
No temperature controller can make the 2 kW system continuously remove a 3 kW load.
Automation vs Remote Monitoring
An app is useful for:
- checking conditions;
- changing settings;
- reviewing climate trends;
- receiving alarms or notifications;
- and supervising the system remotely.
But the fundamental environmental control should be programmed into the controller itself.
Sensor Placement Is Critical
A controller can only respond to the condition measured at its sensor.
The primary sensor should represent the zone you actually want to control.
Avoid Sensor Locations That Are Artificially Hot, Cold, Wet or Dry
Avoid positioning the primary environmental probe:
- directly in an air-conditioner discharge;
- directly in an intake stream;
- immediately in front of an exhaust;
- inside humidifier mist;
- directly over a dehumidifier outlet;
- against a hot light or driver;
- against an external wall;
- in direct radiant heating;
- or in a stagnant corner.
Use More Than One Sensor in Larger Rooms
A single sensor gives one measurement at one location.
It cannot reveal simultaneous hot, cool, humid or dry zones elsewhere in the room.
Positioned at a representative point in the controlled zone.
This is the value the controller uses to operate equipment.
Used to identify the most difficult or potentially unrepresentative area.
It helps confirm that acceptable control at the primary sensor also represents the wider room.
Temperature Trigger Control
A high-temperature trigger can increase cooling-related equipment output when temperature rises above the selected threshold.
For an exhaust fan:
This works only while the intake air is cool enough to remove useful heat.
If the intake is already hotter than the desired room condition, commanding the exhaust fan to maximum does not create refrigeration.
Humidity Trigger Control
A high-humidity trigger can operate equipment intended to reduce room moisture.
Depending on the system, that may include:
- exhaust ventilation;
- a dehumidifier;
- or an integrated HVAC system.
If the incoming humidity ratio is too high, increasing fan speed may do little to reduce moisture or may make the problem worse.
Temperature and Humidity Triggers Can Interact
The same exhaust fan can be called upon for two different reasons:
That can work well when the intake air is simultaneously cooler and drier.
But one requirement can conflict with another.
For example:
Increasing outside-air ventilation may help moisture while increasing the sensible cooling load.
Give Each Piece of Equipment a Clear Job
| Equipment | Main Function | Important Limitation |
|---|---|---|
| Exhaust Fan | Replaces room air | Cooling and drying depend on intake condition |
| Active Intake Fan | Supplies replacement air | Must be balanced with exhaust |
| Circulation Fan | Mixes room air | Does not remove net heat or moisture from room |
| Air Conditioner | Actively removes sensible heat | Cooling capacity must match load |
| Dehumidifier | Actively removes water | Adds sensible heat to room |
| Humidifier | Adds water vapour | Can overshoot if sensor is in mist path |
| Heater | Adds sensible heat | Must not fight cooling equipment unnecessarily |
| Grow Light | Provides light | Also contributes to room energy balance |
Minimum and Maximum Output Levels
Minimum and maximum levels are two of the most useful controller settings.
Defines the lowest output allowed while the automated program is operating.
For an exhaust fan, this can maintain a baseline level of air exchange rather than allowing ventilation to stop completely.
Caps the highest output the program can command.
This can be useful for controlling noise, limiting airflow through a carbon filter or preventing equipment from operating beyond the intended system range.
Controller Level Is Not Airflow Percentage
This is one of the most important concepts when balancing a smart ventilation system.
Delivered airflow depends on:
- fan design;
- fan speed;
- carbon-filter resistance;
- duct resistance;
- intake resistance;
- and the fan operating point.
Two identical controllers can command two fans to the same level while the two duct systems deliver different airflow.
What Are Dynamic Transitions?
A simple on/off controller changes equipment state when a threshold is crossed.
A dynamic transition allows compatible equipment to change output progressively as conditions move further away from the trigger.
For a variable-speed exhaust fan this can provide smoother environmental control than repeatedly switching from low to full speed.
What Is a Controller Buffer?
A buffer creates separation between the condition that turns equipment on and the condition that allows it to turn off again.
This is also known as hysteresis.
For example:
The purpose is to prevent equipment rapidly switching state when the sensor hovers around one threshold.
Avoid Rapid Equipment Cycling
Rapidly switching equipment on and off can create:
- unstable room conditions;
- unnecessary mechanical wear;
- repeated noise changes;
- and poor control.
This can happen when:
- the sensor is positioned in a direct equipment discharge;
- the trigger band is too narrow;
- equipment is substantially oversized;
- or the room is poorly mixed.
What Is VPD Control?
VPD stands for vapour pressure deficit.
It describes the vapour-pressure difference between the plant environment and the moisture-saturated condition at the leaf.
It combines temperature and humidity information into a metric related to the plant's evaporative environment.
Compatible AC Infinity controllers can use high and low VPD triggers to operate connected equipment.
Use:
- VPD for plant environmental control;
- humidity ratio for moisture mass balance;
- dew point for condensation and actual moisture analysis.
Leaf Temperature and VPD
Leaf temperature can differ from room-air temperature because of:
- radiant energy from lighting;
- transpiration;
- air movement;
- and plant physiological conditions.
AC Infinity's Controller 69 Pro and later controllers provide a VPD leaf-offset setting so the VPD calculation can account for an estimated difference between air temperature and leaf temperature.
AC Infinity Controller 69 Family Comparison
AC Infinity's current controller range provides several levels of UIS environmental automation.
| Feature | Controller 69 | Controller 69 Pro | Controller 69 Pro+ | Controller AI+ |
|---|---|---|---|---|
| Physical UIS Ports | 4 | 4 | 8 | 8 |
| Independent Port Programming | Yes | Yes | Yes | Yes |
| 10 Output Levels | Yes | Yes | Yes | Yes |
| Temperature Control | Yes | Yes | Yes | Yes |
| Humidity Control | Yes | Yes | Yes | Yes |
| VPD | Current comparison lists support | Yes | Yes | Yes |
| Timers / Cycles / Schedules | Yes | Yes | Yes | Yes |
| Minimum / Maximum Levels | Yes | Yes | Yes | Yes |
| Dynamic Transitions | Yes | Yes | Yes | Yes |
| Advanced Buffer Features | Model dependent | Model / firmware dependent | Yes | Yes |
| App Connection | Bluetooth | Bluetooth + Wi-Fi | Bluetooth + Wi-Fi | Bluetooth + Wi-Fi |
| AI Automation | No | No | No | Yes |
Controller 69 Pro
The Controller 69 Pro provides four independently programmable UIS ports with Bluetooth and Wi-Fi app connectivity.
Current programming features include:
- temperature triggers;
- humidity triggers;
- VPD control;
- minimum and maximum levels;
- dynamic transitions;
- timers;
- cycles;
- schedules;
- alarms;
- notifications;
- and climate-data monitoring.
It is also supplied with current AC Infinity CLOUDLINE T-Series fan systems.
Controller 69 Pro+
The Controller 69 Pro+ expands the platform to eight independently programmable UIS ports.
This becomes useful when one environmental system contains multiple device types such as:
- exhaust fan;
- active intake;
- circulation fans;
- lighting;
- humidification;
- heating;
- and other UIS-controlled equipment.
Controller AI+
The Controller AI+ adds AC Infinity's AI-based environmental automation layer to an eight-port UIS controller.
AC Infinity currently lists features including:
- AI analysis of environmental patterns;
- dynamic device output;
- eight physical UIS ports;
- support for expanded device groups using splitter hubs;
- dual-zone climate monitoring capability;
- Wi-Fi app control;
- temperature, humidity and VPD monitoring;
- and support for additional sensor types.
AC Infinity currently states that up to 32 UIS devices can be managed when compatible splitter hubs are used.
Automating an Exhaust Fan
A useful exhaust strategy often combines:
- a baseline minimum speed;
- temperature response;
- humidity response;
- a suitable maximum speed;
- and smooth transitions where supported.
Automating Active Intake and Exhaust Together
Where negative pressure is required, delivered active intake airflow should remain below delivered exhaust airflow.
The problem is that two fan controller levels do not necessarily represent the same airflow.
For example:
Check at:
- minimum fan operation;
- normal operation;
- high-temperature operation;
- high-humidity operation;
- and maximum permitted output.
Automating Circulation Fans
Circulation fans redistribute air inside the controlled room.
Their purpose can include:
- reducing temperature stratification;
- mixing humid and dry zones;
- moving conditioned air through the canopy;
- and reducing stagnant areas.
Do not add circulation-fan m³/h to exhaust-fan m³/h when calculating room ventilation.
Lighting Automation
Compatible controllers can also automate lighting schedules and output levels.
Potential functions include:
- on/off schedules;
- brightness levels;
- gradual sunrise transitions;
- gradual sunset transitions;
- and coordinated environmental programs.
- the plant lighting environment;
- and the room sensible heat load.
Coordinate Cooling and Dehumidification
An air conditioner and dehumidifier can affect each other's load.
For example:
Likewise, an air conditioner may provide some moisture removal while it is cooling.
Use Alarms as a Second Layer of Protection
Automation attempts to control normal operation.
Alarms should identify conditions outside the expected operating range.
Useful alarms can include:
- high temperature;
- low temperature;
- high humidity;
- low humidity;
- extreme VPD;
- equipment or sensor faults where supported;
- and unexpected environmental trends.
Plan for Failure Modes
Ask what happens if:
- the internet connection fails;
- the controller loses power;
- a fan stops;
- a sensor becomes inaccurate;
- a dehumidifier tank fills;
- condensate drainage fails;
- an intake becomes blocked;
- or cooling equipment reaches maximum capacity.
Use sensors, alarms and environmental trend data to identify abnormal conditions.
Have an appropriate equipment response, shutdown strategy or manual action.
Confirm how equipment and programs behave after power or communications return.
Use Controller Data to Diagnose the Room
Climate graphs are useful because they reveal patterns that a single current reading cannot.
Look for relationships between:
- lights switching on;
- temperature rise;
- fan output;
- humidity change;
- dehumidifier operation;
- lights switching off;
- and overnight environmental drift.
Commission the System Before Leaving It on Automatic
Do not connect everything, enable automation and assume the settings are correct.
Commission the room systematically.
Environmental Controller Commissioning Checklist
| Check | What You Are Confirming |
|---|---|
| Sensor comparison | Primary probe is reasonably consistent with a trusted reference |
| Sensor location | Reading represents the controlled zone |
| Exhaust minimum | Baseline ventilation is adequate |
| Exhaust maximum | Fan/filter/duct system remains within intended operating range |
| Active intake balance | Desired room-pressure direction is maintained |
| Temperature trigger | Correct equipment responds in the intended direction |
| Humidity trigger | Correct equipment responds without creating an unacceptable temperature problem |
| Transition behaviour | Outputs change smoothly without excessive hunting |
| Buffer behaviour | Equipment does not rapidly toggle around the threshold |
| Maximum-load test | Equipment has enough actual capacity |
| App / alarm test | Notifications work as intended |
| Power recovery | Controller and connected equipment return to the intended operating state |
Common Environmental Controller Mistakes
| Mistake | Why It Causes Problems | Better Approach |
|---|---|---|
| Sensor directly in fan airflow | Reading may not represent the room | Use a representative control location |
| Assuming fan level = airflow % | System resistance changes delivered airflow | Commission actual airflow |
| Setting exhaust maximum too low | Controller cannot access enough capacity | Check required duty point first |
| Running intake and exhaust at same controller level | Does not guarantee neutral airflow | Balance delivered airflow |
| Using exhaust to fix humid outside air | Intake may not provide moisture removal | Compare humidity ratios |
| Using exhaust to cool hot intake air | Ventilation cannot cool below intake temperature | Use active cooling |
| Trigger band too narrow | Can cause repeated cycling | Use suitable transitions/buffers |
| One sensor for a large non-uniform room | Local extremes remain hidden | Verify with secondary sensors |
| Depending entirely on app alerts | Alert does not physically correct failure | Design local controls and fail-safe responses |
| Automating before testing equipment | Control logic hides underlying design problems | Commission manually first |
Continue Designing Your Environmental System
Calculate how much delivered exhaust airflow the room actually requires.
Learn how to balance active intake and exhaust while maintaining the intended pressure direction.
Diagnose airflow, temperature, humidity, pressure and controller problems.
Shop Grow Room Environmental Controllers
Green Genius stocks AC Infinity controllers, smart inline fans and compatible environmental equipment for automated indoor growing systems.
Grow Room Environmental Controller FAQs
What does an environmental controller do in a grow room?
It measures environmental conditions and automatically operates compatible equipment according to programmed temperature, humidity, VPD, time or other control logic.
Where should I place the temperature and humidity probe?
Place it where the reading represents the controlled zone. Avoid direct intake air, exhaust streams, air-conditioner discharge, humidifier mist, local heat sources and stagnant corners.
Does Controller 69 level 5 mean 50% airflow?
No. Controller level represents a device command, not guaranteed delivered airflow. Actual airflow depends on the fan and the resistance of the carbon filter, ducting, intake and other system components.
What is the difference between Controller 69 Pro and Pro+?
The Controller 69 Pro has four UIS device ports while the Pro+ has eight. Both provide independent device programming, Wi-Fi/Bluetooth connectivity and advanced environmental automation.
What does a minimum fan level do?
It keeps the fan operating at or above the selected baseline level even when the primary environmental trigger is not demanding higher output. This can be used to maintain minimum ventilation or circulation.
What does a controller buffer do?
A buffer creates separation between the trigger-on and trigger-off conditions so equipment does not rapidly switch state when the sensor reading fluctuates around a threshold.
Can one controller manage temperature and humidity together?
Yes, compatible controllers can react to multiple environmental variables. However, the connected equipment must be capable of achieving the desired conditions and the different control actions should not unnecessarily fight each other.
Does VPD replace temperature and humidity control?
No. VPD is a useful plant-environment metric derived from temperature, humidity and leaf-temperature relationships. Temperature and humidity remain important physical variables, and humidity ratio remains more useful for moisture mass-balance calculations.
Can a smart controller fix an undersized ventilation system?
No. The controller can optimise the available fan output but cannot make the fan, filter, ducting, cooling or dehumidification system exceed its physical capacity.