@amuseboucheuk welcome to the forums.

Posted by: @amuseboucheuk

↑

I would like to be able to hook into the raw data from the Midea but failing access via an API I could build a Arduino / Raspberry Pi system to collect,. analyse and act on the data.

@cathoderay can probably point you in the right direction.

Posted by: @amuseboucheuk

↑

I would like to be able to hook into the raw data from the Midea but failing access via an API I could build a Arduino / Raspberry Pi system to collect,. analyse and act on the data.

Midea heat pumps have a modbus connection in the wired controller, see your wired controller manual for details. If you are familiar with Arduino/Raspberry Pi systems you probably already know what you need to know access the data. You can even write to (set) some of the registers, for example that is how I adjust my weather compensation curve. 

Posted by: @editor

↑

@cathoderay can probably point you in the right direction.

We cross posted!

Posted by: @amuseboucheuk

↑

We have JUST installed a Midea 16kW R290 AWHP (ASHP) with a 300l / 50l Buffer twin coil cylinder [...]

I'm on the Octopus Cosy Tariff and plan to re arrange the roof:
In the short term we will install a 5kW Hybrid inverter with 11.6kWh EESS (solaX) 

Here's the electrical specification from the installation manual for the Midea 16kW ASHP

So this is 3-phase (?).
The instructions stipulate it should be fused at 20A per phase.

It draws 10.1A per phase each time it starts up (5.9kW),
which drops to 8A once the compressor has brought both loops up to operating pressure.

So...

What's the thinking behind getting a 5kW inverter and 11.6kWh storage battery?

Are you assuming that it would be too expensive to install an inverter & battery combination which could adequately support the ASHP?

Is the 5kW inverter to be 3-phase?

Is there are particular reason you are choosing a solaX battery, which is a 'high voltage' system?

Just completed installing a brand new R290 Midea 16kW unit linked to a 300/50 cyl with additional Solar Thermal Coil.
Currently using the original (15 year old) ST controller but see there is mention of an ST coil in the wiring but nowt in the tech references or user manual as to how it works.

Has anyone else got a similar setup and let me know if this feature replaces the ST controller or if it just stops the AWHP from genernerating when there's ST avaliable.

TIA

Matt 

Hi,

thanks to both for your input.  The media 16 K heat pump I have is a single phase as is the rest of my house my thinking behind the 5 kW inverter is that would be the right size to accommodate the additional 8+6 panels on the roof… In terms of the battery sizing The solar system is expandable in 5.2 kWh modules. I have the space and money for two of those modules at the moment in terms of consumption I will see how it goes… Self generation aside I intend to import electricity on the cozy tariff for use when the rates are higher Buying at 12p and using at 25. 35 once I have some proper data on what I’m actually using, I can expand the battery capacity or not as the data allows

as far as arduino / raspberry pi I would say I’m a bit of a hack. I have one that I built a ozone/sunshine detector with a few years ago so I would have to sit down and remind myself how it’s all programmed!

I saw there was a mod bus connection and also an RS485 data connection. I just wondered as the heat pump is connected to the Wi-Fi whether I could just interrogate an IP address on my local area network to pull out the data.

looking forward to playing with and customising the system!

thanks again for your input. I’m sure we will talk again

Posted by: @amuseboucheuk

↑

I saw there was a mod bus connection and also an RS485 data connection. I just wondered as the heat pump is connected to the Wi-Fi whether I could just interrogate an IP address on my local area network to pull out the data.

Modbus and RS485 are just parts of the same thing, just two bits of the connection.

The Wifi connection is flaky and the Midea App even flakier. Wired modbus is the way to go. I have written up some of what you need to do here on the forum, start here. It's long winded because it is aimed at the 'enthusiastic amateur' who may not yet know what modbus is let alone what it can do. The main difference between my system and others say Home Assistant is that I use python scripts to collect, process and chart the data. I get charts like this:

That's an expensive way of buying battery storage @amuseboucheuk
Have a look at this discussion on A Business Case for Buying a Battery.

The inverter(s) don't need to 'match' your proposed new PV panel output.
An alternative view is that the kW output of your inverter(s) should match the demand you want the battery to support within the home...
... and how much of that you wish to remain live during a power-cut.

I have 7.2kW of solar panels on the (south facing) roof

And I currently have three 5kW inverters.
That 15kW max output is dictated by what I want to be operating.
It includes kettle, oven, microwave, TV, PC, internet etc...  but not the EV charger for example!

 - If one inverter is faulty, then the house can manage on the remaining two.

 - If one of my four 14kWh batteries goes down, there's enough power in the others to last more than 24hrs whilst I resolve the problem.

Thus I have a significant level of resilience built into the arrangement.

There's no single way of viewing what you need.
It depends on your aspirations, rather than a formula.

I'm likely to view things slightly differently to others here on the forum:

• I'm involved in discussions with Government and grid operators on the 'future electricity grid' and the tariffs which are then required
• I can see things from the viewpoint of the grid; I have access to maps and data from National Grid
• I've been trialing and developing battery storage strategies for the past 4-years
• I have a hands-on understanding of the regulations

The benefit of the forum is to hear from a number of differing viewpoints, and thus have the opportunity to evaluate your own thinking accordingly.

 ... which is why I'd like to hear more of what you want to achieve. 😀 

Thank you very much!