Wondering When to Replace Your Greenhouse Controller’s Plug-In Relays?

Consistent maintenance is essential for ensuring optimal performance of your greenhouse controller. One controller component that experiences significant wear and tear are the plug-in relays crucial for smooth operation of your controller.

Before delving into a maintenance schedule for these relays, it’s important to understand their function. The most commonly used relay in our greenhouse controllers (e.g., AegisTec, AegisTecP, and VCU) is a 24-volt DC cube relay (pictured below and available for purchase online).

The relay plays a vital role in the controller. It receives voltage based on your programmed setpoints to engage and close the circuit, subsequently delivering voltage to the appropriate terminal.

For instance, in the image of the AegisTecP relay board below, the circled relays are linked to terminals 3 and 4 to open and close a roof vent. When instructed by the logic board to engage (by sending voltage), a magnetic coil activates and physically engages the contacts, thus closing the circuit and supplying 24 volts to the motor wire.

Relays that control motors may be engaged dozens of times per day depending on controller programming. For instance, if vents are programmed with a short run time and associated dwell time, the vents may cycle on and off 3 or more times to reach the fully open or closed position. Setting the run time no shorter than needed in combination with the dwell time will extend the life of the relays. Cycling on and off is the main factor in relay life; total time of engagement is less important.

All this indicates that relays associated with vents endure substantial wear and tear.

And now to the question posed in the title of this article: When should you replace your relays?

One answer is to say they should be replaced when they begin to malfunction. If the green light is on inside the relay, but voltage is not being sent to the terminal, it is most likely time to replace that relay. Note: A relay reaching the end of its lifespan might work intermittently. (This video walks you through, step-by-step, how to test a relay.)

Finally, we recommend a proactive approach wherein you plan to replace the relays (at least the vent relays) every three years or so. It is possible they can require replacement earlier, and if they fall within the two-year warranty window for our greenhouse controllers, we will send you free replacements. But we recommend you have at least few new plug-in relays on hand once your controller is over two years old to be prepared to replace a malfunctioning relay.

In summary, let’s review some key points:

• Relays providing motor current to vents may undergo many mechanical operations every day and are stressed by cycling large motor currents.

• A general rule of thumb is to be prepared to replace plug-in vent relays every 2-3 years.

Replacement plug-in relays are available online. If you need assistance, do not hesitate to reach out to your customer support team.