How to wire a greenhouse thermostat

Written by elizabeth knoll
  • Share
  • Tweet
  • Share
  • Email

Greenhouses use solar radiation as a means of creating a warmer environment for plants to grow and flourish. The solar radiation can penetrate the transparent walls but not escape. As the weather warms in the spring, the temperature inside the greenhouse will also warm. Eventually the greenhouse will build up too much heat, and this heat will be harmful to the plants. The easiest way to reduce this heat is to connect a reverse thermostat to an exhaust fan. When the temperature reaches a certain reading, the thermostat will turn the exhaust fan on until the temperature falls to an acceptable level. In order to wire a greenhouse thermostat, you'll need a simple set of hand tools.

Skill level:
Moderately Easy

Other People Are Reading

Things you need

  • Line voltage reverse thermostat
  • Tape measure
  • Electrical box
  • Two-conductor electrical wire
  • Electrical fittings
  • Wire nuts
  • Screwdriver
  • Hammer
  • Wire stripper

Show MoreHide


  1. 1

    Purchase a line voltage reverse thermostat. These can be found at your local home improvement store or online.

  2. 2

    Mount an electrical box where you would like to place your thermostat. Ideally it should be about 4 or 5 feet off the floor.

  3. 3

    Run two-conductor electrical wiring from the electrical box to your exhaust fan. Two-conductor electrical wiring has a black (hot) wire, a white (neutral) wire and a green (ground wire).

  4. 4

    Run two-conductor electrical wiring from the electrical box to your circuit breaker panel. Tie the wiring into a circuit breaker as per the local electrical code and the circuit breaker panel manufacturer's recommendations.

  5. 5

    Connect the wiring to the exhaust fan. Refer to the installation manual of the exhaust fan and its wiring diagram to connect the wiring properly.

  6. 6

    Move back to the electrical box and wire in the thermostat. The black (hot) wire from the circuit breaker panel will be connected to the black wire on the line voltage reverse thermostat. The black (hot) wire from the exhaust fan will be connected to the red wire on the thermostat. Use wire nuts for these splices. The white (neutral) wires will be wire nutted together in the electrical box. The green (ground) wires will be connected to the ground screw in the electrical box.

  7. 7

    Mount the thermostat to the electrical box with the provided screws.

  8. 8

    Turn the power on by turning the circuit breaker to the "on" position. Set the thermostat to your desired setting (e.g., If you set the thermostat to 26.7 degrees C, it will kick on when the temperature goes above 26.7 degrees C and turn off when the temperature falls below 26.7 degrees C).

Tips and warnings

  • Check with local electrical codes and ordinances when running the electrical wire. The wire may or may not need to be run in conduit depending on the local code.
  • Keep the thermostat out of locations that receive direct sunlight. Direct sunlight can drastically alter the thermostat's performance.
  • Make sure the power is off to the circuit when working on the wiring. Failure to do so can result in electrical shock or electrocution.

Don't Miss

  • All types
  • Articles
  • Slideshows
  • Videos
  • Most relevant
  • Most popular
  • Most recent

No articles available

No slideshows available

No videos available

By using the site, you consent to the use of cookies. For more information, please see our Cookie policy.