CAPTAIN 8 (AV8) Greenhouse Ventilation Controller – Setup & User Guide

System overview

A greenhouse is like a living room for your plants. To keep them healthy you need to carefully control temperature, humidity, air movement, and light. The ventilation controller is the “brain” that does this work for you.

It connects to vents, fans, heaters, dehumidifiers, lights, and weather sensors. Using timers, setpoints, and safety rules, the controller decides when each piece of equipment should run, keeping the climate inside your greenhouse steady no matter what the weather is doing outside.

What the controller does

• Temperature control: vents open to let heat out, fans move air to cool crops and bring in fresh air, and heaters switch on to keep plants warm at night or on cold days.
• Humidity control: vents crack open briefly to release damp air, fans exhaust humidity and dry leaves faster, and dehumidifiers remove moisture when it is too cold or wet outside to vent.
• Light control: grow lights act like an artificial sun, turning on and off on a set schedule, and light-deprivation curtains close to give crops an artificial “night” even during the day.
• Safety & weather protection: wind sensors close vents and stop fans when it is too windy, rain sensors make vents close to protect crops, and master/slave sensor share lets one greenhouse weather station protect multiple houses.

How it all fits together

• The controller has relay outputs (like light switches) to run vents, fans, heaters, lights, and dehumidifiers.
• It also has inputs for temperature probes, humidity sensors, and weather sensors.
• You program parameters (P-numbers) to tell the controller what equipment is connected, what temperatures or humidity levels to react to, and what times to run special features like DIFs or grow lights.
• Once set, the system works automatically, adjusting the climate minute by minute, protecting plants, and saving energy.

Why it matters for growers

• Healthier plants: stable conditions reduce stress, disease, and uneven growth.
• Higher yields: the right temperature, humidity, and light mean stronger plants and better harvests.
• Energy savings: the controller only runs equipment when it is needed.
• Peace of mind: safety rules protect crops during storms, cold snaps, and hot days.

A quick example day

• Morning: heaters switch on early, vents crack briefly to dry leaves, fans mix the air.
• Midday: vents and fans run together to cool, grow lights turn off.
• Evening: heaters stage on to hold warmth, fans slow down.
• Night: dehumidifier functions remove moisture, heaters keep the crop safe.

In short, the ventilation controller is your greenhouse autopilot. It listens to sensors, follows your programmed setpoints, and coordinates every piece of equipment so your plants stay comfortable and productive all year long. Thank you for buying the CAPTAIN system. It is easy to set up and use, and it helps you control vents, heaters, and fans.

Main features

• Temperature DIFs with manual overrides
• Wind speed sensor option
• Humidity option
• Battery-backed clock
• 8 or 10 relay outputs
• Adjustable temperature settings
• Touch screen display
• Manual overrides

Installing the CAPTAIN

• Protect the enclosure from moisture. Mount it in a secure, dry place.
• Only drill holes in the bottom of the enclosure.

Wiring the temperature sensor

Place the temperature sensor in the middle of the building, or in a location that represents the building’s average temperature. It is important to not let sensors come into contact with direct sunlight.

Connect the temperature sensor to the Sensor #1 terminals. Polarity is not important.

Extending the temperature sensor

1. Run 18–22 AWG wire (twisted or shielded if possible) from the sensor to the CAPTAIN. Keep the sensor wire at least 1 foot away from high-voltage wire, and specifically away from the VFD output wires.
2. Solder or use gel-filled crimps to connect your wires to the temperature sensor.

Developer feature: 3 temperature probes

Up to 3 probes can be connected. You will need to move the #1 jumper to the T position. If using probe #4, jumper 1 must be in the T position.

Connecting the wind meter

A wind meter closes vents in high wind. Wind data can be shared wirelessly between units.

Mounting the wind meter

• Put the sensor outside where it can catch wind from all directions.
• Mount it upright with the rotating cups on top.

What if nothing shows up?

If you do not see any wind speed, you need to adjust the config settings: set P29 = 1.

If the wind meter is spinning but the screen still says zero miles per hour (MPH) for a whole minute, then something is definitely wired wrong.

Connecting a rain sensor

You can connect a rain sensor to the system. The rain sensor closes select vent motors when it is raining. The system supports 1 rain sensor.

If you connect a rain sensor, the controller needs to know it. Setup parameters P40 and P41 assign the sensor to the vent motors.

Installing the rain sensor

When you are installing the wires, keep the rain sensor cord 6 inches away from high-voltage wires. The vent motor’s close signal is activated when the sensor is wetted; the position of the sensor versus the sky dictates the response. The wire colors are marked on the board and match the sensor’s cord. Wire by connecting the colors.

Troubleshooting the rain sensor

Quick test: make your hand wet and vigorously rub the clear dome of the sensor. About 30 seconds of rubbing should trigger rain. There is a faint click and a dim green LED turns on when triggered.

Controller does not detect rain: do the quick test. If rain is detected at the sensor, check the sensor connections and wiring back to the controller. All connections need to be dry and corrosion-free. Wet or corroded connections need to be replaced.

Rain sensitivity

The rain sensitivity can be adjusted. However, it does require that you take the rain sensor apart. Take the 4 screws out that hold the sensor together to access the switches inside. Adjust the switches as noted below. Be careful to keep the gasket in place when reassembling.

Sensitivity settings (switches 1 & 2)

The sensor has 4 sensitivity settings. DIP switches 1 and 2 set the rain detect threshold.

15-minute delay after it stopped raining: normally the vent reopens after it stopped raining. If you want it to stay closed for a while after the rain, set DIP switch 3 on. Normally we want #3 off, so vents reopen sooner.

Connecting a humidity sensor

The humidity sensor allows you to monitor and control the humidity. If humidity is too high, a vent can open or a fan can start. If you connect a humidity sensor, it needs to be activated; activate it by selecting humidity for setup parameter P10.

Location of the humidity sensor

Mount in a central location. Keep the sensor away from heaters, or you will get a low reading when the heater is running.

Installing the humidity sensor

Route humidity sensor wires 6 inches away from high-voltage wires.

Powering the CAPTAIN

• AC versions come with a power cord. Plug it into a 120v outlet. Requires 120V, 5 amp.
• DC versions are either 12 or 24 vdc. Check the voltage labeled on your unit.

Controller relay outputs

There are 8 output relays on the CAPTAIN 8. The first 6 are replaceable and have NO & NC contacts, with a maximum of 0.3 hp or 7.5 amps, whichever is less. They also have a green mechanical test button, used to manually activate the contacts.

The last pair, 7 & 8, are smaller, have only NO contact, and are not field replaceable. Maximum of 3 amps. No motor loads.

Each button on the screen and the output terminals are associated with the corresponding relays.

Motor connector bus bars

The motor connector bars are for low-voltage motors only. By default the CAPTAIN 8 includes bus bars for the first 6 relays / 3 vents. If you want to repurpose any of outputs 6, 5, 4, 3, 2, or 1 for another app (remapping), the bus bars must be removed from the remapped outputs. This is done by removing the bus bar entirely, snipping it with pliers, and reinstalling it on the correct outputs.

Bus bars can be reduced or removed to allow fans, heaters, or lights to be connected instead of vent motors. To shorten them, remove the connector completely, then use pliers to snip it to length. With the bus bar removed, the outputs become dry contact.

Connecting fans

Fans can be controlled, but you need contactors to switch the fans’ electricity. Outputs 7 & 8 are dry contact. AutoVent contactor boxes are available for easy wiring.

Motor & device wiring examples

Connecting 2 vents, 1 cooling, 2 heat

Relays 6 or less can be remapped from their default of low-voltage vents. If remapping #6 or less, the aluminum bus bar must be shortened.

Connect to heaters

Several zones of heaters can be connected. Use output relays 7 & 8 for heaters or fans. Connect the heater’s signal wires to the controller as shown.

Connecting DC motors

If the controller has a PS suffix on the part number, it includes a 24v motor supply. PS models are prewired to run several DC vent motors. Connect motors directly to the board as shown (connector bars installed).

Vent motor circuit breakers

There are several vent motor breakers. Each of them protects a motor. If a motor’s amps go too high, the center tab trips out. Press the tab in to reset.

Can I connect two motors to the same circuit?

For example, one motor spot on the controller would instead be wired with two motors, and they would both run together. It depends. If both motors run fine without tripping a 5 amp circuit breaker, it likely will work. You will be responsible for getting both motors to run in the same direction. It also increases the risk of a tripped circuit breaker affecting a larger area.

How big a DC motor can the CAPTAIN 8 power supply run?

It depends, mainly on how hard it starts and moves. A rule of thumb: if it rarely trips a 7.5 amp circuit breaker, it likely will work. The life of the replaceable relays will be reduced if it starts hard.

Screen overview & overrides

The screen shows you what is happening. You can see the temperature and the status of the relays. Press on the temperature to go to your settings. Press the bottom row of buttons for manual overrides.

Overrides

The overrides allow you to force an output. In Auto, it operates automatically. Selecting Off or Forced allows you to avoid the control system. The app’s temperature is shown, and all contributing probes are highlighted. To exit, press the blank space on the sides.

Temperature DIFs

Your greenhouse controller has a feature called Temperature DIFs. DIFs let you temporarily change the temperature setpoints during certain times of the day. In the morning, DIFs can help dry out the greenhouse by warming and venting more. In the late day, DIFs can help hold in heat by adjusting when vents open or close. Think of DIFs as a way to “bend” your normal heating and cooling rules for a short time to help the crop.

How DIFs work

• The status screen shows you when a DIF is active.
• If you pressed “Force On,” the screen will also show that DIF is running, even outside its normal schedule.
• To change when DIFs happen, press the clock button. DIF override buttons allow you to manually override any clock settings.

In simple terms

• Normal mode: vents open when it is too hot.
• DIF1 (morning): vents open a little sooner to dry the greenhouse.
• DIF2 (evening): vents close a little later to keep in warmth.
• You set the times and temperatures, and the controller does the rest.

• P500–P503: DIF1 timers. Set start and stop times for DIF1 (morning drying).
• P504–P507: DIF2 timers. Set start and stop times for DIF2 (late-day heat trap).
• Each DIF can also have a 2nd on/off time if you want two cycles per day.

Parameter reference

There are parameters that you can change. The parameters are labeled P1, P2, and so on. These parameters are the temperature setpoints and values you can adjust. From the parameter screen you can scroll between parameters and edit each parameter ID.

Vent parameters

Normal operation: vents open when the greenhouse is warm and close when it cools down. In the morning (DIF1), vents may open earlier to push out damp morning air. In the afternoon/evening (DIF2), vents may adjust differently to trap warmth. If it gets too humid, a vent will crack open briefly to dry the air, unless it is too cold. If it is windy or raining, vents will close safely and wait until conditions improve. The controller does all this automatically once you set the parameters.

Wind settings

Imagine the CAPTAIN 8 closing the ridge or side vents when the wind is super strong. This helps lower the risk of your building getting blown apart. You set how strong the wind has to be before it closes the windows; this is called the “High Wind Event.” When the wind is higher than your number, the vents close. When the wind slows, they open again. The “Clear MPH” number is how slow the wind must be before the vent can open again. Make sure this number is smaller than your “High Wind Event” number, otherwise they may cycle all the time and wear out your system early.

Fan settings

You can tell the fans to turn on when it gets too hot. Set a temperature setpoint for each fan, and when the room gets hotter than that number, the fans start blowing. When the room cools down a bit, the fans turn off. Too much wet air (humidity) can make plants sick; with a humidity sensor, the fans will turn on to dry the air out and stop once it gets less wet. If you have staged fans that need to stop when it gets too hot, you can set a special “too hot” number. In normal mode, fans turn on when the greenhouse warms above their setpoint and turn off once it cools below the gap. In the morning (DIF1) fans may come on earlier to help push out damp air; in the afternoon (DIF2) they may run differently to manage late-day heat. If the outside wind is too strong, fans can shut down until conditions are safe.

Variable-speed (VFD) fans

A VFD makes 3-phase fans go fast or slow, but it does not tell the fans when to start (that is a different relay). The fans go slower when it is cooler and faster when it is hotter, like a ramp. When it is really cool, the fans run at a slow, steady speed. When it is really hot, the fans go at 100% speed. You can also tell the fans to go at one speed all the time by setting a manual speed.

Heater parameters

Heaters keep your greenhouse warm so plants stay healthy. The controller decides when to turn heaters on or off based on the temperature you set. If you only have one heater, it is simple: the controller just turns it on and off at the right temperature. If you have multiple heaters, they can be staged: heater 1 comes on first, then heater 2 joins in if the greenhouse keeps cooling, and so on with heater 3, heater 4, and so on. When the greenhouse warms up again, they shut off in reverse order. This keeps heating smooth and steady instead of all at once.

Dehumidifier parameters

The dehumidifier only runs when the greenhouse is too humid. Once it is on, it keeps running until the humidity falls below the start humidity minus the hysteresis buffer. This prevents rapid cycling, saves energy, and keeps plant conditions stable.

Light DEP parameters

These parameters control the light deprivation settings. The Light DEP logic allows you to close shades and vents when DEP is activated. Afterward, the vents wait 2 minutes in the reopen sequence. Light DEP shades only move when the shade time has elapsed. If the vents are set to respond with the light DEP, they will close as well.

Grow light control (the “sun clock”)

Grow lights are like an artificial sun for your plants. With the controller you can set exactly when the lights should turn on and off, so your plants get the right amount of “daylight” every day. At the on time, the grow lights turn on automatically and stay on, providing light like the sun, until the off time. If a 2nd cycle is programmed, the lights turn on again at the 2nd on time and turn off at the 2nd off time. If the second cycle is not programmed (still set to 0:00), the lights stay off after the first cycle.

Hardware setup & configuration

Put it all together: define what equipment you have (vents, fans, heaters, lights, dehumidifier); assign relays so the controller knows which switch powers each device; enable sensors (temperature, humidity, wind, rain) so the controller knows what conditions to react to; and link probes to devices so each vent, fan, or heater responds to the right temperature reading. Once the hardware setup is programmed, the controller knows exactly what equipment is installed, how to control it, and which sensors to listen to.

Dehumidifier strategy

Your controller can use vents, fans, and the dehumidifier individually or as a team. Your greenhouse stays drier, your plants stay healthier, and you save energy by only using the equipment that is needed.

• Morning strategy: use heaters plus a short venting period to quickly dry off leaves after sunrise.
• Winter strategy: rely more on the dehumidifier when it is too cold to vent.
• Summer strategy: let fans and vents carry most of the load, since outside air is usually drier than inside.

Vents – letting moist air escape

When humidity rises above the setpoint, the controller can crack open a vent for a short time. This lets moist, heavy air escape upward while drier outside air comes in. Vents will not open if it is too cold (set by the humidity low-temperature limit) or if wind/rain is unsafe.

Fans – mixing & exhausting air

Fans help pull humid air out and bring in fresh air. They can be set to run when humidity passes a certain level. Fans also keep air moving inside, which helps leaves dry faster. If the wind is too strong (and a wind sensor is connected), fans may pause for safety.

Dehumidifier – drying without venting

The dehumidifier works when the greenhouse is above a humidity setpoint. It is a machine that pulls water out of the air directly, without opening vents; however, it takes a lot of electricity. This is most useful when it is too cold or wet outside to vent, but inside humidity still needs to drop. A small hysteresis buffer prevents it from switching on and off too quickly.

Sensor share (master/slave)

Sometimes you have more than one greenhouse, but you do not want to buy a separate wind and rain sensor for every house. Sensor Share lets one “Master” controller send its sensor readings to other “Slave” controllers. This way, multiple houses can share the same weather information.

• Master: think of the Master as the “weather station.” It sends out wind and rain data once per second, and all the other houses can listen to it.
• Slave: these controllers do not have their own weather sensors. Instead, they “listen” to the Master’s data and act on it. This saves money and keeps all houses reacting the same way to storms.

How to set it up

• Master: set P38 = 1 to turn the controller into a Master that talks once per second. To send wind data, also enable the wind sensor with P29. Rain status is always sent, even if wind is not.
• Slave: set P38 = 2 to turn the controller into a Slave that listens. To receive wind data, enable the wind sensor with P29. Rain status is always received, no matter what.

Radio connections

Connect radios as shown. The controllers talk via radios once per second. The TX and RX lights will blink accordingly.

Diagnostics: the PWR LED needs to be on all the time. RX is when the radio hears something; TX is when it talks. If a Slave never hears anything, check if the Master’s TX light comes on once per second.

Channels: the radio uses channels, like a walkie-talkie. Dip switches 1, 2, 3, and 4 pick the channel. If all the switches are off, it is channel 0. If you have two unrelated systems close together, put them on different channels so they do not get mixed up. Any combination of the switches being on or off will work, for 16 combinations total. Just make sure all the controls you want to work together have the same switch combination.

Boost: the boost switch makes the radio signal stronger. Only use boost if the controls are not talking to each other very well, since a stronger signal can mess with other devices and might make the radio break sooner. The radio should normally work up to 1000 feet if there is nothing in the way. Metal walls or screens will block the radio signal.

Slave connectivity indicator: a red “!!!” means it is a Slave and no messages were heard in the last 3 seconds; “TX” means it is the Master; “.:|” means it is receiving messages.

Sharing sensor information with wires (RS-485)

Sometimes you can use wires instead of radio waves to share information from sensors. It is like using a telephone line instead of a walkie-talkie. The wires are connected in a line, like a chain (daisy-chained), using 4-conductor twisted-pair 18-gauge shielded wire. Even though it is wires, you still need to set up all the numbers and settings as if it was using a radio (P38, P29, channels).

• Only one end of the shield. Only connect one end of the shield to ground. If you connect both ends, it can cause problems and make the sensors act weird.
• Do not mix with big power. If high voltage accidentally touches these wires, all the controllers will be instantly ruined.
• Long wires and thunderstorms. Long wires can attract lightning, like a tall tree. Try to keep the wires as short as you can. The wires can be up to 4,000 feet in theory, but it is proven to work well up to 1,000 feet, depending on the gauge and load.
• Use the right kind of wire. Follow TIA/EIA-485 standards. Some good companies that make these wires are Carol, Alpha Wire, Tyco/Raychem, and Belden. For best results, search “RS-485 best wiring practices.”

Remapping outputs

Imagine the controller is like a phone, and it has different apps that do different jobs. We can change which apps the controller uses. Changing the apps is called “remapping.” It is like changing the buttons on a video game controller to do different things. Remapping is a super advanced job, and you can only do it in a special place called the “setup menu.” If you want to see how to remap the apps, search YouTube for AutoVent LLC Captain.

Putting it all together

1. Define what equipment you have (vents, fans, heaters, lights, dehumidifier).
2. Assign relays so the controller knows which switch powers each device.
3. Enable sensors (temperature, humidity, wind, rain) so the controller knows what conditions to react to.
4. Link probes to devices so each vent, fan, or heater responds to the right temperature reading.

Troubleshooting

Controller continually reboots

Does it show an error right as it turns on? Most likely this is a software bug or a parameter out of range. Report the error code and controller version number to tech support.

Does the controller reboot randomly? First, confirm 120v is consistent on the L and N terminals of the RS-15-24 power supply. If not, check the incoming power circuit.

If power is good, disconnect all rain, humidity, and wind sensors:

• If it stops rebooting with only the temperature sensor connected, a sensor is likely overloading the supply. Check the sensor wires and sensors.
• If it still reboots, check whether the reboot coincides with another device turning off or on. If so, see how that device is interlinked and disconnect it.

If none of that resolves it, work through these in order of significance:

1. Turn the power-supply voltage adjustment so the supply puts out about 23v (rare, but above 24v can be an issue). Compare your meter with a known DC voltage elsewhere.
2. Change the power supply – a bad power supply could do it.
3. Pull all relays out and check them – a shorted relay could cause it.
4. Change the lid.

The screen is on but I cannot do anything with it

Likely the touch panel is out of calibration. You can recalibrate it. Tools needed: a short piece of wire stripped on both ends.

Entering calibration:

1. Fasten an end of the short piece of wire on Input #2.
2. Turn power off and back on again.
3. Wait for it to show the Recalibrate screen.
4. Bump the loose end of the jumper against Common 3 times (Input #2 needs to be pulsed to Common 3x while the screen shows Recalibrate).

The screen will show: “Steadily touch the first calibration point.” Then press the 5 calibration dots in sequence (use a pencil eraser). When finished, the controller will restart. If touch is still not working, try recalibration again. If it still does not work, make sure the bezel or enclosure is not putting tension on the screen. Tension, twisting, or moisture can cause the touchpad’s touch resistors to change. The screen and touchpad are replaceable if needed.

Specifications

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