Grant Aerona3 ASHP Modbus

I’ve no experience of this myself, but it looks like it’s possible to get some data from a Grant ASHP via modbus. It sounds like the Grant Aerona3 has modbus built in as standard, no additional module required.

Unfortunately looking at the list of registers available, there’s not enough data to calculate COP. For that we would need FlowT, ReturnT, electrical power and flow rate. So it looks like a 3rd party heat and electricity meters would still be required to enable COP to be calculated. But it may be possible to read mode registers that are not documented yet?

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I’m new to ASHP, but in the process of getting a Grant Aerona3 ASHP. I was wanting to try and calculate COP, but it seems from your comment this might not be possible.

I assume from the GitHub - aerona-chofu-ashp/modbus: Draft Modbus mappings it is possible to get Flow Temp, Return Temp and Outside Temp. Plus along with a CT clamp around the input electricity supply it should be possible to get energy consumption.

Is the only information we’re missing a heat meter input? I’m afraid I have no idea what that is / or what it means? Is this something that can be added or we’ll always be missing from a Aerona3 ASHP?



You’re just missing flow rate. The heat delivered can be calculated from flow and return temperature and flow rate.