The WILLHI WH2408 is a plug-in temperature controller that switches a heater or fan on and off at the temperatures you set with two dials, with no menus to scroll through. It works for greenhouses, chicken coops, attic fans, seedling mats, incubators, fermentation, and smokehouses, and it keeps your settings after a power outage.
The included probe is waterproof and food grade, while the controller housing itself should be kept dry, so mount it out of the weather.
Specifications
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Probe Range: -58°F to 230°F (-50°C to 110°C)
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Controller Ambient Range: -4°F to 140°F (-20°C to 60°C)
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Power Rating: 1200W at 120V
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Control Resolution: 0.1°F
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Modes: Heating or cooling
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Controls: Two knobs for on and off temperatures
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Probe: Waterproof and food grade, with a tip approximately 1.5 inches long
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Settings Memory: Retains settings after a power outage
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Housing: Fire retardant ABS shell with internal power isolation
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Electrical Protection: Resettable fuse and ETL listed power cord
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Display: Adjustable brightness with Fahrenheit or Celsius readout
Switching a Heater or Fan by Temperature in a Greenhouse, Coop, or Outbuilding
If you have one heater or one fan that needs to run only when a space gets too cold or too hot, this controller handles it without any programming. You set the turn on temperature with one dial and the turn off temperature with the other, and the controller cuts or restores power to whatever is plugged into it.
That makes it practical for keeping a backyard coop above freezing, venting a hot attic or greenhouse, or protecting supplies in a pump house or storage shed through winter. Because the probe is food grade, you can also use it for sous vide, meat curing, or brewing. If your heater draws more than 1200W, plan on a lower wattage setting or a smaller unit.
What to Expect from the WILLHI WH2408 in Real Use
Verified purchasers lean heavily on how simple the two dial setup is, with several saying they never needed the manual. Setting the on temperature above or below the off temperature determines whether the outlet cools or heats.
Owners run it on attic and garage ventilation fans, with one set to start at 90°F and run until the space falls to 80°F, and on a small greenhouse cycling between roughly 87°F and 85°F. Readings are described as accurate, though a grower advises keeping the probe out of direct sunlight.
For winter heat, a pump house owner holds a space heater between 40°F and 45°F and values that the controller fully de-energizes the heater. That same owner had the onboard 10 amp breaker trip after months on a 1300W setting, then switched to a 900W setting with no further trips.
Another grower reported repeated tripping that left plants exposed overnight, so keep your heat source for the greenhouse under 1200W and check on it. The unit connects by a short cord rather than plugging straight into the wall, so plan to mount or hang it.
Real-world performance notes sourced in part from verified Amazon customer purchases.
Frequently Asked Questions
What size heater can I use with the WILLHI WH2408?
The WH2408 is rated for 1200W at 120V and has an onboard 10 amp breaker that trips if the load runs above that. Many milk house style space heaters run at 1300W or 1500W, which can trip the breaker and leave the heater off until you press the reset button. Use a heater with a setting at or below 1200W, such as a 700W or 900W setting, especially in a building you do not check every day.
How do I set the WILLHI thermostat to run an attic or greenhouse fan?
Set the on temperature higher than the off temperature, and the controller works in cooling mode. For example, setting the fan to turn on at 90°F and off at 80°F will run it whenever the space reaches 90°F and shut it off once the temperature drops to 80°F. Reverse the two settings, with the on temperature lower than the off temperature, to control a heater instead.
Where should I place the WILLHI temperature probe?
Place the probe in the area whose temperature you want to control, keeping it out of direct sunlight so it does not read higher than the actual air temperature. The probe is waterproof and food grade, so it can go into liquids or directly against food for sous vide, curing, or fermentation. The probe lead also lets you keep the controller housing in a dry spot away from the heater or fan, since the controller itself should not get wet.
