Greenhouse Thermostat Buying Guide

Control the temperature in your greenhouse with a thermostat. This device operates the heating, cooling and ventilation systems to maintain an appropriate temperature for the plants you are growing. Not only will this ensure the survival of the plants, but it will also encourage plants to flourish and produce more. You get what you pay for with thermostats, whether it’s better accuracy, more options or both.

Different Ways to Control Greenhouse Temperature

Maintaining the temperature in your greenhouse will typically combine air conditioning, heating and ventilation technologies. You can have separate thermostats for each device, but you will have better control and higher system efficiency if you have one device that controls them all.

Accuracy

The quality of a thermostat comes down to the degree of accuracy built into it. The difference between the set point temperature at which a thermostat turns off and the set point temperature at which it turns back on is called the temperature differential. The differential is the degree of accuracy of the thermostat and the temperature swing under which your greenhouse plants must be able to survive and flourish.

Temperature Differential Function

In general, better thermostats have smaller temperature differentials and best thermostats have adjustable temperature differentials. A differential that is too small or too large for your greenhouse heating, air conditioning and ventilation system can cause system imbalance, short cycling or other malfunction. The adjustable temperature differential is very helpful for balancing the environmental temperature control system.

Heat Anticipator Function

The nature of greenhouses lend themselves to rapid solar heat gain or loss from a cold winter night. This can also unbalance your environmental temperature control systems by exceeding the differential much faster than the thermostat and control system can respond.

Some thermostats feature an adjustable heat anticipator to compensate for large temperature swings. This feature can also be useful if your greenhouse has large thermal mass.

Remote Temperature Sensor Feature

For accurate control, place your thermostat at plant height in the center of the greenhouse. It should be sheltered from direct sunlight and in the mix of the air circulating within the greenhouse. Some thermostats feature a remote temperature sensor, which can simply the process of finding the right spot.

Use a Relay

You can use relays to adapt a single thermostat to various temperature control devices.

Portable Cord-Connected Thermostats

For smaller applications, use portable thermostats with cords. Make sure the electrical loads of the devices connected to these devices do not exceed 80 percent of the electrical load capacity rating of the thermostat. Don’t guess—do the math. Avoid a fire.