Why do room temperature and drive mode appear to come from the same register?

Both parameters are mapped to register address 0 on the A1M. The template handles this by reading the same address and interpreting the value according to the parameter context. No manual adjustment is needed.

What baud rate and serial settings should I use?

The default is 9600 baud, 8 data bits, no parity, 1 stop bit (9600 8N1). Make sure both the gateway and the A1M module are configured identically.

Can I control multiple indoor units from one gateway?

Yes. Each indoor unit requires its own MelcoBEMS Mini (A1M) module with a unique Modbus slave address. Connect all modules on the same RS-485 bus and add each as a separate device in ModbusCloud.

Write commands do not seem to take effect. What should I check?

Verify that the A1M module is set to allow external Modbus write access. Some installations have write protection enabled by default. Also confirm the correct slave address and that no other BMS is holding write priority on the bus.

How it works Pricing

Try the demo Shop

Dutch company. EU-hosted. GDPR-compliant.

Product

Gateway
Shop
Diagnostics
How it works
Pricing
Try the demo

Company

About us
Knowledge Base
Templates
Contact

Legal

Privacy policy
Terms and conditions
Data Processing Agreement
Cookies
Impressum

Free Modbus template: MelcoBEMS Mini (A1M) | ModbusCloud

///MelcoBEMS Mini (A1M)

Modbus RTU

MelcoBEMS Mini (A1M)

Name: MelcoBEMS Mini (A1M)
Brand: Mitsubishi
SKU: c5a616b9-2c20-4ab7-9743-a3fd7d92e2ed

Mitsubishi

Controls Mitsubishi HVAC units via MelcoBEMS Mini (A1M) Modbus interface

Overview

This template connects to the Mitsubishi MelcoBEMS Mini (A1M) Modbus RTU interface. It provides read and write access to HVAC parameters such as room temperature, setpoint, fan speed, air direction, drive mode, and on/off control.

Key readings

Room Temperature
Drive Mode
Temperature Setpoint
Fan Speed
Air Direction
Drive On/Off

Available commands

Temperature Setpoint

Fan Speed

Air Direction

Drive On/Off

Use cases

Monitor room temperature and setpoint on a live cloud dashboard for each Mitsubishi indoor unit.
Adjust temperature setpoints remotely to reduce energy consumption outside of occupied hours.
Create an alert when room temperature deviates from the setpoint by more than 2 degrees for over 15 minutes.
Log fan speed and air direction changes over time to verify scheduled HVAC profiles.
Switch drive on or off remotely for seasonal shutdown or startup without an on-site visit.
Compare drive mode and room temperature across multiple zones in a multi-unit installation.

Installation

1Wire the RS-485 A and B terminals from your ModbusCloud gateway (MCG or MLP series) to the corresponding Modbus terminals on the MelcoBEMS Mini (A1M) module.
2Set the Modbus slave address on the A1M module using its DIP switches or configuration menu, and note the address for use in the template.
3Confirm that the baud rate on the A1M is set to 9600, matching the default for this template.
4Import the Mitsubishi MelcoBEMS Mini (A1M) template in the ModbusCloud platform and assign the correct slave address.
5Verify communication by checking that room temperature and drive status values appear on the cloud dashboard.
6If controlling multiple indoor units, repeat the wiring and address assignment for each A1M module and add each as a separate device in ModbusCloud.

Things to watch for

Why do room temperature and drive mode appear to come from the same register?: Both parameters are mapped to register address 0 on the A1M. The template handles this by reading the same address and interpreting the value according to the parameter context. No manual adjustment is needed.
What baud rate and serial settings should I use?: The default is 9600 baud, 8 data bits, no parity, 1 stop bit (9600 8N1). Make sure both the gateway and the A1M module are configured identically.
Can I control multiple indoor units from one gateway?: Yes. Each indoor unit requires its own MelcoBEMS Mini (A1M) module with a unique Modbus slave address. Connect all modules on the same RS-485 bus and add each as a separate device in ModbusCloud.
Write commands do not seem to take effect. What should I check?: Verify that the A1M module is set to allow external Modbus write access. Some installations have write protection enabled by default. Also confirm the correct slave address and that no other BMS is holding write priority on the bus.

Registers (6)

6 read / 5 write

Name	Address	Function	Type	Unit	Access
Room Temperature	0	FC04	uint16	°C	R/W
Drive Mode	0	FC03	uint16		R
Temperature Setpoint	1	FC03	uint16	°C	R/W
Fan Speed	2	FC03	uint16		R/W
Air Direction	3	FC04	uint16		R/W
Drive On_Off	7	FC03	uint16		R/W

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.

See the live demo How it works

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

Specifications

Protocol: Modbus RTU
Brand: Mitsubishi
Registers: 6
Compatible models: MelcoBEMS Mini (A1M)
Last updated: 17 April 2026

Want to professionalise your projects?

EU-hosted

Data in the Netherlands and Germany

Open standard

Based on Modbus RTU/TCP

Free to browse

No account or payment required

European company

Based in the Netherlands