Daikin DCOM gateways for Altherma - MODBUS ENG

Use cases

• Monitor leaving water, return water, and DHW temperatures on a live cloud dashboard for each Altherma installation.
• Create an alert when the unit error code register changes from zero to detect faults before the end user notices.
• Adjust heating or cooling LWT setpoints remotely to optimise comfort and energy consumption without a site visit.
• Log outside air temperature alongside flow rate to analyse seasonal heat pump performance over time.
• Switch DHW reheat on or off based on time schedules or external triggers configured in ModbusCloud.
• Enable quiet mode during nighttime hours to comply with local noise regulations in residential areas.

Installation

1. 1Connect the RS-485 A and B terminals of the DCOM gateway to the corresponding terminals on your ModbusCloud gateway (MCG or MLP series), and ensure a common ground reference.
2. 2Set the DCOM gateway Modbus slave address using its DIP switches or configuration interface, and note the address for the template setup.
3. 3Verify that the DCOM gateway is configured for 9600 baud, 8 data bits, no parity, and 1 stop bit, which matches the template defaults.
4. 4In the ModbusCloud portal, create a new device, select the Daikin DCOM Altherma template from the library, and enter the slave address you configured.
5. 5Confirm communication by checking that live temperature readings appear on the device detail page within a few seconds of saving.

Things to watch for

01

The gateway is not responding. What should I check first?

Verify the RS-485 wiring polarity (A to A, B to B) and confirm that the slave address set on the DCOM gateway matches the address entered in ModbusCloud. Also check that the baud rate is 9600 on both sides.

02

Temperature readings show unexpected values. How are they scaled?

All temperature registers return values in degrees Celsius as int16. Some DCOM firmware versions use a factor of 10 (e.g., 225 means 22.5 degrees). Check your DCOM documentation and apply the correct scaling in the template if needed.

03

Can I connect multiple DCOM gateways on the same RS-485 bus?

Yes. Assign a unique Modbus slave address to each DCOM gateway and add a separate device in ModbusCloud for each one using the same template. Keep total cable length within RS-485 limits and add a 120 ohm termination resistor at each end of the bus.

04

Do I need to enable Modbus on the DCOM gateway separately?

On most DCOM-LT models, Modbus RTU is enabled by default on the RS-485 port. On the DCOM gateway for Altherma v3, verify in the gateway configuration menu that the Modbus interface is active.

Registers (31)

19 read / 12 write

More Daikin templates

Daikin RTD-NET Module

Daikin

Modbus RTU

Controls and monitors Daikin HVAC units via RTD-NET Modbus interface.

15 registers152

Daikin RTD-RA Module

Daikin

Modbus RTU

Controls and monitors Daikin split AC units via RTD-RA Modbus interface.

9 registers43

Daikin HomeHub air2air (SG Ready)

Daikin

Modbus TCP

3 registers

Daikin HomeHub (SG Ready)

Daikin

Modbus TCP

5 registers

Daikin Heating & Cooling

Daikin

Modbus TCP

Controls Daikin Altherma heat pumps via Modbus TCP or RTU through the HomeHub interface.

42 registers110

Daikin AC EKMBDXA 7 Zones

Daikin

Modbus RTU

Controls and monitors Daikin VRV air conditioning across 7 zones via Modbus

42 registers56

More RTU templates

Alnor HRU-P

Alnor Systemy Wentylacji Sp. z o. o.

Modbus RTU

Controls Alnor HRU-P heat recovery ventilation units via Modbus RTU.

49 registers7

Alnor HRU

Alnor Systemy Wentylacji Sp. z o. o.

Modbus RTU

Controls and monitors Alnor heat recovery ventilation units via Modbus RTU.

29 registers13

Wattsonic - Schmachtl Sun Energy Box

Wattsonic

Modbus RTU

Monitors Schmachtl Wattsonic hybrid inverter via Modbus RTU

92 registers72

Heidelberg Wallbox Energy Control

AMPERFIED GmbH

Modbus RTU

Controls and monitors Heidelberg Wallbox Energy Control EV charger via Modbus RTU.

22 registers67

connecdoor.controller

connecdoor

Modbus RTU

Controls and monitors smart door access points via RS485

0 registers53

Belimo Air-Water Actuator Modbus RTU

Belimo

Modbus RTU

Controls communicative damper and valve actuators via Modbus RTU.

20 registers46