The N321S is a controller intended for solar water heating applications. It controls the water circulation system based on the difference of temperature between the solar collector and the storage tank (or swimming pool).

The instrument contains two NTC-type temperature sensors and a control output for activating the water circulation pump. It provides protections against overheating and freezing to the piping, preventing damages to the system.

- NTC Thermistor: 10 kΩ @ 25 °C, range: -30 to +105°C (-22 to 221 °F), Accuracy: 0,6 °C (1,1 ºF)
- Sensor interchangeability: 0,75 ºC (1,35 ºF)
- Measurement Resolution: 0,1º from –19.9 to 119.9º
- Output: Relay SPDT, 1 HP 250 Vac / 1/3 HP 125 Vac (16 A Resistive)
- POWER SUPPLY: 100 to 240 Vac/dc ±10%
- Optionally: 12 to 30 Vdc/ac
- Mains Frequency: 50~60 Hz
- Power Consumption: 5 VA
- Dimensions: 75 x 33 x 75 mm
- Weight: 100 g
- Panel: 70 x 29 mm

Parameter Name	Parameter Value
Display	digital
Type	water and oil circulation
Use	heating
Maximum temperature (°C)	-30 - 105