Measures three-phase active and reactive energy for class B/class 1 metering.
Overview
The Circutor CEM-C21 is a static three-phase energy meter supporting class B active energy (EN50470) and optional class 2 reactive energy. This ModbusCloud template reads per-phase voltage, power, reactive power, power factor, and total power over Modbus RTU at 9600 baud.
Key readings
Voltage F1 to F3
Power F1 to F3
Total Power
Reactive Power
Cos phi F1 to F3
Use cases
Monitor per-phase voltage and power on a live cloud dashboard to detect load imbalances across three phases.
Log total active and reactive energy consumption over time for tenant billing or energy audits.
Create an alert when power factor drops below a threshold to identify potential power quality issues.
Compare energy usage across multiple CEM-C21 meters installed at different distribution boards in one building.
Generate daily or monthly energy reports for facility managers without visiting the site.
Installation
1Wire the Circutor CEM-C21 to the ModbusCloud gateway (MCG or MLP series) using a shielded RS-485 cable, connecting A, B, and GND terminals.
2Set a unique Modbus RTU slave address on the CEM-C21 using the front panel buttons, and note this address for gateway configuration.
3Confirm the CEM-C21 baud rate is set to 9600 (factory default) to match the template settings.
4In the ModbusCloud platform, add a new device and import the Circutor CEM-C21 template from the template library.
5Enter the configured Modbus slave address in the device settings and verify that live readings appear on the dashboard.
Things to watch for
01
Why does the Cos phi F3 reading show incorrect values?
The Cos phi F3 register at address 1858 uses uint16 data format, while all other registers use int32. Ensure the register data type is set correctly. The ModbusCloud template already accounts for this difference.
02
The gateway cannot communicate with the CEM-C21. What should I check?
Verify that the RS-485 wiring is correct (A to A, B to B, GND to GND). Confirm the baud rate is 9600 and the slave address on the meter matches the address configured in the gateway. Check that the RS-485 bus is terminated if the cable run exceeds 10 meters.
03
Can I connect multiple CEM-C21 meters on the same RS-485 bus?
Yes. Assign each meter a unique Modbus slave address. Add a separate device entry in ModbusCloud for each meter using the same template. Ensure proper bus termination at both ends of the RS-485 line.
04
Does this template support reactive energy readings?
The template reads reactive power registers. Reactive energy measurement requires the optional class 2 variant of the CEM-C21. If your meter does not have this option, reactive registers may return zero.
Registers (11)
11 read / 0 write
Name
Address
Function
Type
Unit
Access
Power F1
1860
FC03
int32
W
R
Power F2
1862
FC03
int32
W
R
Power F3
1864
FC03
int32
W
R
Power
1866
FC03
int32
W
R
Reactive Power
1876
FC03
int32
var
R
Voltage F1
1842
FC03
int32
V
R
Voltage F2
1844
FC03
int32
V
R
Voltage F3
1846
FC03
int32
V
R
Cos phi F1
1854
FC03
int32
R
Cos phi F2
1856
FC03
int32
R
Cos phi F3
1858
FC04
uint16
R
Working with Modbus in your projects?
ModbusCloud is the hardware-plus-software platform that installers use to monitor, visualise and control Modbus devices from one portal. This template is one of hundreds you can use right away.
