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Autovent 3

"State of the Art Control For Hi-Tech Greenhouses"

  • Suits most types of roof and/or side vented greenhouse.
  • Four time zones to allow detailed profiling of environment.
  • Three stage fan plus pad evaporative cooling
  • Automatic switch over from passive venting to fan/pad.
  • Heating – proportional or ON/OFF.
  • Fogging control for cooling or humidity control - pulsed.
  • Advanced algorithm for venting and heating to give good control of temperature and humidity including purging sequences.
  • Two stage stirring fan control.
  • Two levels of shading with inside/outside selection.
  • Supplemental lighting control – two levels.
  • Thermal blanket or blackout photoperiod control.
  • CO2 injection.
  • Single weather station for multiple AutoVent3 controllers.
  • PC interface with remote setting, data logging, event logs etc.


The AV3 can operate with any mixture of vents and fan/pad evaporative cooling. If both are available it will start cooling by operating the vents but if this is unsuccessful in reducing the temperature, the vents will close and the fan/pad will start. If only fan/pad is provided then cooling will start with single stage fan exhaust and if this is unsuccessful in controlling the temperature it will add stages and/or pad one at a time.

If the temperature remains above the set-point when all stages and the pad are operating, then shading will be applied to try to assist.

The venting algorithm will try to control both temperature AND relative humidity. If heating is available then this too will be used to try to control humidity in addition to temperature.

Any combination of vents can be controlled including twin independent roof (gull wing), saw tooth, single or twin side walls. The roof venting uses an intelligent algorithm to adjust the nudge size taking into account present roof position, size of error, rate of error change, differential temperature (inside - outside) and wind effect.

The change over to fan/pad and back has a differential (settable) to prevent frequent switching back and forth and can only change back to passive venting twice within each time zone

The 3 stage fans come on in sequence and the pad is normally added between the first and second stages unless the humidity is very high (settable) in which case it will activate between the second and third stage unless extremely high when it activates only after the third stage fan has come on.


Air heating can be by either proportional control or ON/OFF control. Proportional control is normally used in conjunction with a boiler heating water pipes. This provides a very gentle heat and the heating pipes can be positioned either under the grow beds or between the rows of plants. In this way less heat need be supplied as compared with general warm-air heating. Water pipe heating is gentle, economical and avoids sudden drying of the air. The heating is used to control both the temperature and the relative humidity.


Fogging may be used instead of fan/pad to assist with cooling. The fogging may also be used to increase humidity in dry weather. Two outputs are used; one that comes on constantly while fogging is called for and another that pulses on for short periods to inject puffs of fog.

Stirring fans

Two stages of stirring is provided. The first stage will always be on when the vents are closed and exhaust fans are stopped. The second stage will also come on when the temperature or humidity is high. Both fans may be set to come on when fogging is active.


In the event of very high humidity, the controller can be programmed to go into a purging mode. In this mode it increases the heating temperature by a few degrees (user set) to try to dry the air. Eventually the humidity will creep up again due to plant transpiration and the controller will nudge open the vents (or if no vents or in fan mode will switch on an exhaust fan) for a few seconds (user set) to exhaust the warm humid air. Then the vents will close (or fans turn off) and the heater will again warm and dry the fresh air. This purging cycle will continue until the humidity is brought under control.


Two stages of shading and one thermal blanket or blackout screen control are provided. The shades may be designated as inside or outside. If outside then they are withdrawn in the event of strong wind or rain.

Normally they operate as follows:-At a set time each morning or if the light exceeds a user set level screen 1 will close. If the light exceeds a second user set level then shade two will close and when closed shade 1 will open. If the light exceeds a third user set level then both shades will close.

At least one screen will always be closed during the day until the evening time is reached. Then both screens will open if the light level permits

Screens will close after the light level exceeds the set point for 1 minute but will only reopen when the light is below the setpoint for 15 minutes.

The thermal blanket closes at a set time each evening. If roof vented then this is on provision that the temperature and humidity are within limits. The thermal screen opens when the temperature exceeds the day-time venting temperature. If temperature or humidity become excessive and if the house is roof vented then the thermal screen will crack to 15% open. This will happen before venting or purging is initiated. Alternatively, the thermal blanket output may be used for blackout cloth applications for photoperiod manipulation.

CO2 Injection

CO2 is measured and injected to achieve a user set point providing 1) there is sufficient light AND 2) the venting is below a user-set limit. The user may specify any desired level of CO2 from 0 to 2000ppm and the system will try to provide this when the above conditions are satisfied.


Two stages of supplemental lighting are available and can be used to extend the hours of daylight for photoperiod manipulation or else to top-up the available sun light to achieve a set integrated value for the day. This may be achieved by setting them to come on when the day light falls below a certain level and then also switching them on during hours of darkness to achieve a set daily integrated value.