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This wiki is intended to describe configuration and use of the R32-based air source heat pumps manufactured by Chofu Seisakusho Co. Ltd. in Japan. In the UK, Ireland and France they are rebranded by Grant as the Aerona3 heat pumps, while in other markets distributors sell them with the Chofu brand.
In particular, the way they are typically installed in the UK ignores many of the capabilities of the heat pump and can lead to a sub-optimal experience. This wiki and repositories aim to gradually document some of the available settings and features.
We are not responsible for anything you choose to do with the information here. Some may be based on supposition and guesswork and could be wrong. It is presented on a best-effort basis, but anything you do is at your own risk. This is site is not endorsed by Grant or Chofu.
Due to differing national standardisation criteria, environmental conditions, and possibly software and settings, the exact specifications of the units vary between countries. Not all models are offered in all markets. However there are a number of distinct chassis:
| Rating | Grant | Chofu |
|---|---|---|
| 6kW | HPID6R32 | AEYC-0643XU-CH |
| 10kW | HPID10R32 | AEYC-1043XU-CH |
| 13/12kW | HPID13R32 | AEYC-1242XU-CH |
| 17/16kW | HPID17R32 | AEYC-1643XU-CH |
- Grant Aerona3 Installation Manual (September 2020)
- Chofu R32 Operating/Installation Manual (New Zealand)
- Chofu AEYC Service Manual
The Chofu installation manual is recommended as the starting point to understand your unit. The Grant manual is based on the Chofu manual but with many sections removed - the main useful difference is the specifications (which differ slightly for the UK) and the wiring diagrams, which are likely how a UK installer has wired it. The Chofu service manual contains a full list of the (many) settings codes, as well as disassembly instructions.
The docs repo has more documentation from Chofu and Grant, including in other countries and related models of heat pump. If you have any other useful documentation you would like to submit, feel free to follow the Github flow to fork the docs repo and create a pull request.
- Modbus reverse engineering
-
Reverse Engineering Grant ASHP Remote Protocol
- the protocol between the ASHP and the indoor control panel