Programmable Two-stage Temperature Controller

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Model: TD420A

$84.99

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Product Update (4/16/2025): A new model TD420A with upgraded firmware is now available to replace the older model TD420P. A user can now program up to 8 steps with more flexibility to achieve single-step, multiple-step, and infinite loops. The TD420A user manual will be available soon.

The TD420P temperature controller has one output for cooling control and another for heating control. This can be used for applications such as beer fermentation or converting a refrigerator to a kegerator. The temperature control can be programmed to different set temperatures at different time steps. Up to 8 temperature-time steps covering up to 33 days can be programmed. Utilizing both cooling and heating device control, refrigerators can be controlled at specific temperatures regardless of the environmental climate.

No wiring is needed for this plug-n-play controller. Users only need to plug in the power cord from the heater/cooler to the output sockets on the controller. Both heating and cooling control modes are simple on/off control, similar to a mechanical thermostat but with much higher precision due to an adjustable hysteresis band, precision sensor, and digital readout. An anti-short function is available to protect the compressor from frequently cycling on/off with high-pressure Freon.

Unlike other two-stage temperature controllers with economic NTC/PTC thermistor sensors, a digital silicon band gap sensor is used in this controller. The advantage of this digital sensor is its reliability in moist environments than a thermistor sensor. It can be fully immersed in water over extended periods without any issues, and perform with more precision and uniform accuracy over an entire specific temperature range. In addition, the cable of the sensor comes with food-grade silicone insulation, as compared to PVC jackets used on most sensors on the market. Silicone is safer than PVC for food applications, especially when immersed in solutions that contain alcohol. This is because flexible PVC contains plasticizers that can leach out in alcohol. Silicone is also able to withstand higher temperatures.

Note: this controller is only compatible with a silicone bandgap sensor. It is not compatible with PT100 RTD sensors.

Specifications:

Temperature Control Range	-50 ~ 105°C, -58 ~ 221°F
Temperature Resolution	0.1°C (between -9.9 ~ 99°C) 1°C (between -50 ~ 10°C, 100 ~ 120°C) 0.1°F (between -9.9 ~ 99.9°F ) 1°F (between -58 ~ 10°F, 100 ~ 248°F)
Temperature Accuracy	0.5 °C or 0.9 °F
Temperature Control Mode	On/Off Control. Heating and Cooling
Temperature Control Output	10 A, 120 V or 240 V AC *
Timer Range	Each step: 0.1 to 99.9 Hrs or 1 to 999 Mins
Timer Resolution	0.1 hours or 1 Minute
Max Programmable Time	799.2 hours or 33.3 days (for a total of 8 steps)
Audio Alarm	High and low limit
Sensor Type	Silicon Band Gap Sensor
Sensor Size	0.24" OD. (6.0 mm), 2" Length (50 mm)
Ambient Temperature	-20~ 50 °C
Dimension	91 x 140 x 46mm
Input Power	85 ~ 242 VAC, 50 Hz / 60 Hz
Sensor Cable Length	6 ft (2 m)
Power Cable Length	3 ft (1 m)

Warranty: One (1) year limited warranty. See here for details.

Note:

The controller can display temperature in Celsius or Fahrenheit.
Unlike other PID controllers that we sell, this on/off controller will not hold temperature as tight if the system has a very slow and delayed response. Some temperature overshoot is normal.
Either heating or cooling device is limited to 10 Amps. The output voltage is the same as the input voltage. When the controller is plugged into 120 VAC, the output will be 120VAC. If the controller is connected to 240 VAC, the output will be 240 VAC.
The input power plug is a US NEMA 5-15P plug. The output sockets are US NEMA 5-15R. Optional input & output travel plug adapters are offered. Please check here for more details.