The RS485 version of the N321S is a controller originally intended for solar water heating applications, harnessing renewable energy by controlling liquid or air circulation based on the temperature difference between two supplied NTC sensors (included). In a solar application, the control output activates the water circulation pump to maintain an even temperature between the solar collector and storage tank — useful for swimming pools, hot tubs, and hot water recycling systems. For air destratification/circulation, the control output activates a high-level fan to keep an even temperature throughout a building's layers, eliminating heat wasted at the top of warehouses, factories, or agricultural buildings. It's also used to cool grain stores and maintain the correct differential. As part of a solar system it also provides protection against overheating and freezing to the piping, preventing damage to the system.
This version contains additional wiring terminals and firmware suitable for RS485 serial communication, allowing integration with SCADA or a PLC via Modbus.
✅ 3 Year Manufacturer Warranty — backed by our UK-based technical support
Novus N321-S Datasheet Download
Novus N321-S Modbus Register Table
Technical Details
NTC Thermistor: 10 kΩ @ 25°C, range: -30 to +105°C (-22 to 221°F), Accuracy: 0.6°C (1.1°F)
Sensor interchangeability: 0.75°C (1.35°F). Measurement Resolution: 0.1° from -19.9 to 119.9°
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
Frequently Asked Questions
What can I read via Modbus?
The full Modbus Register Table is linked above, covering the readable/writable registers for SCADA or PLC integration.
Does this still work as a standalone controller if I don't connect RS485?
Yes — RS485 is an optional extra for remote monitoring; the controller functions as a standard standalone N321S without it.
Is there a version without RS485?
Yes, see the standard N321S.
Industry Applications
- SCADA-Integrated Solar Systems — RS485 Modbus allows centralised monitoring across multiple controllers.
- Solar Water Heating — maintains even temperature between collector and storage tank, protecting against overheat and freeze.
- Building Air Destratification — activates high-level fans to redistribute trapped heat in warehouses and agricultural buildings.