The ERC does not answer on the bus. What should I check?

The ERC has no RS485 terminals; communication needs a TTL to RS485 converter on the programming port. Check that o03 is set to an address from 1 to 247 (default 0), that the master uses 19200 baud, 8E1, and swap A and B on the converter side if needed.

Why do temperatures read 250 instead of 2.5 °C?

Temperatures are signed 16-bit integers with scale 0.01. The template applies the scale; if you read the registers yourself, divide by 100.

Some registers return an exception.

Not every register exists on every model. The fan, defrost and alarm relays, DI2 and the fan parameters are only on the ERC 213 and 214, the light relay and DO4 config only on the ERC 214, Cooling Heating only on the ERC 211. The comment of each register names the models.

Writing the sensor type or application has no effect.

Parameters o06, o61, o07, o36 and o71 can only be changed when regulation is stopped. Write 0 to Main Switch first, change the parameter and switch regulation on again.

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Modbus RTU

Danfoss ERC 21x

Name: Danfoss ERC 21x
Brand: Danfoss
SKU: f588f1c2-dcc1-45fb-b280-fdae5f4278f6

Danfoss

Refrigeration controller: temperatures, relay states, setpoints, alarm and defrost parameters over Modbus RTU.

Overview

The Danfoss ERC 211, 213 and 214 are refrigeration controllers for cold rooms and display cases with one, three or four relays; this template follows the Danfoss ERC 21X Modbus parameter guide and reads temperatures, inputs and relay states and writes all setpoint, alarm, defrost, fan and compressor parameters. Connection through a TTL to RS485 converter at 19200 baud, 8 data bits, even parity, 1 stop bit, with the address set in o03.

Key readings

Air temperature Sair and regulation reference
Defrost and condenser temperature
Controller status
Compressor, fan, defrost, alarm and light relay status
Digital inputs and night mode
Relay counters and firmware version

Available commands

Main switch r12
Setpoint, differential and setpoint limits
High and low temperature alarm limits and delays
Defrost type, interval, stop temperature and times
Fan and compressor timers
Inputs, outputs, polarity and keyboard lock

Use cases

Alert when Air Temperature Sair rises above High Temperature Alarm Limit for longer than Alarm Delay in a cold room.
Log Compressor Relay Status and Defrost Relay Status to check defrost cycles and compressor running time.
Watch Condenser Temperature Sc to plan condenser cleaning before Condenser High Block Limit stops the compressor.
Change Setpoint remotely for night or weekend operation of a display case.
Read Relay 1 Counter to plan relay replacement on a heavily switching controller.

Installation

1Connect the ERC programming port through a TTL to RS485 converter to the RS485 port of your ModbusCloud Gateway. Terminate both ends of the bus.
2On the controller set the Modbus address in parameter o03 to a value from 1 to 247; the default 0 does not answer.
3In ModbusCloud, add a Modbus device (RTU) with that address, 19200 baud, 8 data bits, even parity and 1 stop bit, then import this template.
4Check the link: Air Temperature Sair should match the controller display and Setpoint the value of r00.

Things to watch for

The ERC does not answer on the bus. What should I check?: The ERC has no RS485 terminals; communication needs a TTL to RS485 converter on the programming port. Check that o03 is set to an address from 1 to 247 (default 0), that the master uses 19200 baud, 8E1, and swap A and B on the converter side if needed.
Why do temperatures read 250 instead of 2.5 °C?: Temperatures are signed 16-bit integers with scale 0.01. The template applies the scale; if you read the registers yourself, divide by 100.
Some registers return an exception.: Not every register exists on every model. The fan, defrost and alarm relays, DI2 and the fan parameters are only on the ERC 213 and 214, the light relay and DO4 config only on the ERC 214, Cooling Heating only on the ERC 211. The comment of each register names the models.
Writing the sensor type or application has no effect.: Parameters o06, o61, o07, o36 and o71 can only be changed when regulation is stopped. Write 0 to Main Switch first, change the parameter and switch regulation on again.

Registers (80)

80 read / 62 write

Name	Address	Function	Type	Unit	Access
Controller Status	•••	•••	•••		R
Air Temperature Sair	•••	•••	•••	°C	R
Read The Present Regulation Reference	•••	•••	•••	°C	R
Condenser Temperature Sc	•••	•••	•••	°C	R
Di1 Input	•••	•••	•••		R
Status on Night Operation	•••	•••	•••		R
Compressor Relay Status	•••	•••	•••		R
Firmware Version Readout	•••	•••	•••		R
Defrost Sensor Temperature Sdef	•••	•••	•••	°C	R
Di2 Input	•••	•••	•••		R
Fan Relay Status	•••	•••	•••		R
Defrost Relay Status	•••	•••	•••		R
Alarm Relay Status	•••	•••	•••		R
Light Relay Status	•••	•••	•••		R
Main Switch	•••	•••	•••		R/W
Setpoint	•••	•••	•••	°C	R/W
Predefined Applications	•••	•••	•••		R/W
Sensor Type Selection	•••	•••	•••		R/W
Differential	•••	•••	•••	K	R/W
Min Setpoint Limitation	•••	•••	•••	°C	R/W
Max Setpoint Limitation	•••	•••	•••	°C	R/W
Display Offset	•••	•••	•••	K	R/W
Display Unit	•••	•••	•••		R/W
Calibration of Sair	•••	•••	•••	K	R/W
Night Setback ECO Mode	•••	•••	•••	K	R/W
Value of Reference Displacement	•••	•••	•••	°C	R/W
Compressor Runtime Continuous Cycle	•••	•••	•••	min	R/W
Setpoint at Continuous Cycle Exit	•••	•••	•••	°C	R/W
Alarm Delay	•••	•••	•••	min	R/W
Alarm Delay Pulldown Start up Defrost	•••	•••	•••	min	R/W
High Temperature Alarm Limit	•••	•••	•••	°C	R/W
Low Temperature Alarm Limit	•••	•••	•••	°C	R/W
DI1 Delay	•••	•••	•••	min	R/W
Condenser High Alarm Limit	•••	•••	•••	°C	R/W
Condenser High Block Limit	•••	•••	•••	°C	R/W
Voltage Protection	•••	•••	•••		R/W
Minimum Cut-in Voltage	•••	•••	•••	V	R/W
Minimum Cut-out Voltage	•••	•••	•••	V	R/W
Maximum Voltage	•••	•••	•••	V	R/W
Defrost Type	•••	•••	•••		R/W
Defrost Stop Temperature	•••	•••	•••	°C	R/W
Defrost Interval	•••	•••	•••	h	R/W
Max Defrost Time	•••	•••	•••	min	R/W
Defrost Delay at Power up	•••	•••	•••	min	R/W
Drip Delay	•••	•••	•••	min	R/W
Defrost Stop Sensor	•••	•••	•••		R/W
Compressor Accumulated Runtime to Start Defrost	•••	•••	•••	h	R/W
Defrost Delay After Continuous Cycle	•••	•••	•••	min	R/W
Compressor Min ON Time	•••	•••	•••	min	R/W
Compressor Min OFF Time	•••	•••	•••	min	R/W
Compressor OFF Delay at Open Door	•••	•••	•••		R/W
Zero Crossing Selection	•••	•••	•••		R/W
Delay of Outputs at Startup	•••	•••	•••	s	R/W
DI1 Configuration	•••	•••	•••		R/W
Serial Address	•••	•••	•••		R/W
Password	•••	•••	•••		R/W
Cooling Heating	•••	•••	•••		R/W
Display Resolution	•••	•••	•••		R/W
Relay 1 Counter	•••	•••	•••		R
Save Settings As Factory	•••	•••	•••		R/W
Display at Defrost	•••	•••	•••		R/W
DI1 Input Polarity	•••	•••	•••		R/W
Key Board Lock	•••	•••	•••		R/W
DO2 Config	•••	•••	•••		R/W
DI2 Delay	•••	•••	•••	min	R/W
Fan Delay After Defrost	•••	•••	•••	min	R/W
Fan Start Temperature After Defrost	•••	•••	•••	°C	R/W
Fan During Defrost	•••	•••	•••		R/W
Defrost on Demand	•••	•••	•••	K	R/W
Fan at Comp OFF	•••	•••	•••		R/W
Fan Stop Evap Temperature	•••	•••	•••	°C	R/W
Fan ON Cycle	•••	•••	•••	min	R/W
Fan OFF Cycle	•••	•••	•••	min	R/W
Relay 2 Counter	•••	•••	•••		R
Relay 3 Counter	•••	•••	•••		R
DI2 Config	•••	•••	•••		R/W
DI2 Input Polarity	•••	•••	•••		R/W
Invert Alarm Relay	•••	•••	•••		R/W
Relay 4 Counter	•••	•••	•••		R
DO4 Config	•••	•••	•••		R/W

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