Mitsubishi Heat Pump Data in Home Assistant via Modbus

This article shows how to get detailed information about your Mitsubishi heat pump’s status and operations into Home Assistant.

Prerequisites

You’ll need a Mitsubishi Modbus interface, either the older A1M (serial Modbus/RTU via RS-485 only) or the newer A1M+ (Modbus/TCP via Ethernet in addition to Modbux/RTU). I’m using the Ethernet variant.

To help you find and order the device:

  • Full name: Procon MelcoBEMS MINI (A1M+)
  • Part number: 700342

Notes:

  • The Modbus interface is connected to the heat pump via Mitsubishi’s CN105 port.
  • As Mitsubishi heat pumps seem to only have a single CN105 connector, you cannot use more than one interface at a time.
  • Documentation is a little hard to come by, but Mitsubishi’s UK site has what we need.

Setting Up the Modbus Interface

Connecting the A1M+ to Your Network

The manual states that the Modbus interface has the factory default IP address 192.168.92.114. What it doesn’t tell you:

  • That IP address is only reachable after you power-cyle the A1M+ by disconnecting the CN105 connector from the heat pump
    • The A1M+ has a reset button, but that doesn’t seem to affect networking.
  • DHCP is off by default and can only be enabled via the interface’s (simplistic) web UI.
  • Once you enable DHCP, you need to power-cycle the A1M+ again.

A1M+ Firmware Update

The manual states that the interface’s firmware can be updated, but it doesn’t specify where to find new firmware. If you have any pointers, please let us know by commenting on this article.

Home Assistant Configuration

I’m providing a configuration package for Home Assistant via this GitHub repository. It converts the Modbus registers I find most useful into HA entities.

Each register/entity is labeled with the English and German names (as comments). Numbers used as enums in Modbus to indicate a certain state are converted to their string representations.

Alternative Interfaces

There are several potential alternatives to Mitsubishi’s Modbus interfaces, but I don’t recommend any of them. These alternative interfaces are connected to the heat pump via the single CN105 port, so you cannot connect more than one device at a time.

KNX

Note: Mitsubishi doesn’t offer KNX interfaces of its own, but seems to be distributing Intesis devices.

Intesis

  • I found no website or documentation.
  • Might only be for air conditioners.

BES (Ingenium)

  • Might only be for air conditioners.

Zennio

  • Website
  • Officially only compatible up to the FTC6 version of the control board (current heat pumps come with the FTC7).
  • Zennio Support told me that the FTC6 and FTC7 protocols are compatible, but they won’t guarantee compatibility.

Mitsubishi Procon MelcoEcodan Smart Control

  • Very limited functionality.
  • If connected, the heat pump can only be controlled via this interface (the built-in touch screen seems to be disabled).
Heat PumpHome AssistantMitsubishiModbus

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