@cathoderay what is the setting for room thermostat ? (bottom lines of 1st page of instructions)

@tasos — I know I write long posts and things can get lost, but I have already answered this, I can't set the wired controller room stat, when I go to the left hand side of the main page, I get the 'Weather temp set function is on. Do you want to turn off it?' message. I think this behaviour happens because of my TEMP TYPE SETTINGS (which I have never knowingly changed), ie they are as shown in the manual:

I always interpreted the message ('Weather temp set function...') as meaning weather compensation (it fits with the words) but I now believe it is in fact referring to the TEMP TYPE SETTING.

Also, don't forget my wired controller is in the airing cupboard, what I would actually be setting (if I could set it) is the ACAT. Great for the blankets, but perhaps less so for mere humans scattered elsewhere in the building.   

Edited as posted too early by mistake...

@cathoderay 

Based on your data graphs I am also of the opinion that you run wc and the only plausible explanations I can think of are a) either your script commands overwrite the wired controller when executed or b) we (I to be more precise) are missing something fundamental in understanding the process to setup your unit and the implications of each step

The operation of our unit is way much simpler (we have yet to enter Serviceman menu whereas in your instructions it is part of the std process!). Here are some screenshots regarding how we enable weather compensation (custom or std curve). Regarding Room set temperature, it is set manually in the very first screen (the one with the house image I posted earlier).

Regarding the curve type, you are presented with 3 options, each with a different menu

- Standard, in which case you can select which one you will use (from 1 to 8) plus any offset value

- Custom, with a submenu where you set the two end points of the curve

- ECO, with a timer option (I believe you can chose another curve for the remaining period but I have not tried it)

Looks to me , the difference in our systems is like using an early ‘00’s GPRS phone vs an iphone… :-). For sure they have made end user life easier!

Edit: Now that I am thinking of it, I cannot see how I could set a fixed LWT,  but may be this is because I told the installer that we want wc and in order to enable fixed LWT you need to enter Serviceman menu. And I believe the GUI options would change if LWT were enbled

Posted by: @mk4

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the only plausible explanations I can think of [for it not turning things off?] are a) either your script commands overwrite the wired controller when executed or b) we (I to be more precise) are missing something fundamental in understanding the process to setup your unit and the implications of each step

It's either (a) the FOR SERVICEMAN menu entry and exit are bypassed, or, perhaps more likely, (b) my script does turn the DHW heating off when it changes the WCC settings (but not when it just reads them?) and so I make sure it doesn't run when the unit is in DHE heating mode.

I mentioned the code has a check in it to determine whether the DHW heating is on: 

    # check DHW is NOT running (use three port two way valve position) 

    on_off = instrument.read_register(129, 0)
    valve_pos = "{:08b}".format(on_off)[-5]      # 1 = DHW is on, 0 = DHW is off

    # note valve_pos is a string, not an integer, hence need '0' not 0
    if valve_pos == '0':

        # get a datetime for logging
        now = datetime.now()
        now = now.strftime("%Y-%m-%dT%H:%M:%S")

    etc etc

I have documented how but not why! It uses the position of the three port two way valve, which is stored in a single bit in register address 129: the code reads all of register 129, which contains a hex number, and then the next line converts it to a binary number and then pulls out the relevant bit, and if that bit is 0 as opposed to 1, then the unit is not in DHW heating mode, and the rest of the code can proceed.

The question is why did I add that code??? A very distant memory vaguely suggest it is there to make sure the code doesn't run when the DHW heating is on, because if it does, it will turn the DHW heating off.     

The display on the controller has moved on in leaps and bounds! The actual display of the WCC chart is excellent, it will certainly help people who are more visually minded, and it is good that it is freely available with having to go into the FOR SERVICEMAN menu, which on my wired controller looks more like DOS than a noughties GSM phone!  

Posted by: @mk4

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Edit: Now that I am thinking of it, I cannot see how I could set a fixed LWT,  but may be this is because I told the installer that we want wc and in order to enable fixed LWT you need to enter Serviceman menu. And I believe the GUI options would change if LWT were enbled

I think this is the whole point, both of out units are running on pure weather compensation, which means you can't set a fixed LWT, the option disappears. A very long time ago (it seems a lot happened a very long time ago) I'm pretty sure I set up the unit to run with a fixed LWT, to see how it got on (answer if I recall correctly: badly, energy use shot up), but that happened before I had modbus monitoring set up so there are very few records if any. I think I just learnt the point, always run on weather compensation, and forgot about how to do fixed LWT temps. I will however go through my old paper work and see if there are any clues in there.  

Posted by: @cathoderay

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A very long time ago (it seems a lot happened a very long time ago) I'm pretty sure I set up the unit to run with a fixed LWT, to see how it got on (answer if I recall correctly: badly, energy use shot up), but that happened before I had modbus monitoring set up so there are very few records if any. I think I just learnt the point, always run on weather compensation, and forgot about how to do fixed LWT temps. I will however go through my old paper work and see if there are any clues in there.  

I've been playing around with disabling weather compensation on the heat pump itself and use custom logic in Home Assistant to determine the LWT and also set that as a fixed value. To be able to do that, I disable weather compensation using modbus register 5/bit 12 (Climate curve setting (Zone 1), 1: valid; 0: invalid). I assume you also have this set to on in your situation, which should indeed enable WCC combined with water flow temperature control.

A snipper from a Bosch Compress 2000 AWF manual, which is also a Midea, but they tend to have better manuals for it

All other manuals state that WCC will work when "Room Temperature", which is from the wired controller, is enabled. But it does not say it will NOT work if water flow temperature is enabled, which is also what the Bosch manual states and what you, and I, see on our heat pumps

I have at least found the dates when I ran the fixed LWT trial, it was in early April 2022, but not exactly how I did it (possibly Menu > PRESET TEMPERATURE > PRESET TEMP?). I do have some data I collected manually, but it is not very much, just twice a day readings of OAT, LWT and RWT (and some room temps but they were all OK ie within range so not included here, it is the LWT in relation to the OAT we are interested in). This is what I have (note the design LWT was 55°C, hence starting at that value, I then dropped it to 50° as 55° was overcooking things): 

Not exactly an over-abundance of data, but nonetheless is appears to at least be consistent with a fixed LWT, all the LWT values are close-ish to the set value, regardless of OAT, apart from the 2°C OAT value, when the LWT was lower, very likely as a result of a defrost cycle. The 11 Apr 22 2000 LWT value is particularly telling, 50°C despite an OAT of 15°C. On weather compensation, the LWT would be closer to 30°C.  

Posted by: @mosibi

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All other manuals state that WCC will work when "Room Temperature", which is from the wired controller, is enabled. But it does not say it will NOT work if water flow temperature is enabled, which is also what the Bosch manual states and what you, and I, see on our heat pumps

Interesting, especially the observation that it doesn't say it will NOT work with WATER FLOW TEMP enabled. I hadn't realised you see the same behaviour as I do, this obviously makes it more likely we are looking at default behaviour (albeit on the basis of n=2 at the moment...).

And in considering that, I have realised there is another point of confusion! The TEMP TYPE SETTINGS entry is WATER FLOW TEMP, but the message barring me from setting the LWT on the home page is 'Weather temp set function is on. Do you want to turn off it?' which may mean weather compensation after all, ie it is saying the PRESET TEMPERATURE page is on WEATHER TEMP SET (which is where I turn on weather compensation), do I want to turn it to PRESET TEMP, which will turn off weather compensation.

@cathoderay

I am impressed that you recorded and maintained this data! Regarding the Bosch manual, I think we can always rely on Germans to be 100% precise and leave no room for doubt… Specially when compared to AI translated Chinese manuals. 

On the topic of ASHP cycling, do you think I can (to some extend) rely on the data recorded by our PV inverter? Below are the snapshots of the last 4 days. One can see that for time being we operate (on purpose) the ASHP for 10 to 12 hours per day (the morning spikes are due to the kettle..). If we are to believe this data, the ASHP hardly cycles at all (just once or twice a day). Could that really be so???

I should perhaps also mention that while the ASHP is operating, IAT slowly raises by 1.5 to 2 degrees until it reaches the schedule milestone to switch off. And there is a notable difference to the time it takes for the house to cool down (compared to the oil heating). It looses up to 2 degrees by the time the ASHP switches on. The range we are talking about is 18.5 to 20.5 degrees (as measured by our old Siemens thermostat, which is our baseline for IAT measurements). Of course OAT plays a critical role, but the last couple of days are typical of the season.

I guess working with lower temperatures allows the thermal mass of the house to store more energy (our house does have a large thermal mass, concrete skeleton with double external brick walls, having an external insulation also supports the storage of energy in its mass).

Overall, we are very comfortable, but I still need to get used to the radiators not being blazing hot…..

Posted by: @mk4

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...

Overall, we are very comfortable, but I still need to get used to the radiators not being blazing hot…..

...

I was having just this discussion with the engineer who came last Friday for our annual heat pump service. We were both mentioning times we've heard people pointing out the truism that you don't want a warm radiator; you want a warm room.

I do agree that it takes a little time to change your mindset but at the same time the lack of apparent direct heat source is exactly what helps make the environment in a heat pump home more natural and comfortable than a fossil fuel heated one.

Posted by: @mk4

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On the topic of ASHP cycling, do you think I can (to some extend) rely on the data recorded by our PV inverter?

I think it will depend on the resolution of the data, adequate plotting (portrait on a mobile could so squish the data together you lose detail), and being sure that there is no other energy in source and equally sure they are no other major loads.

Posted by: @mk4

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The range we are talking about is 18.5 to 20.5 degrees

That diurnal variation is quite large, but of course is to be expected with a long overnight setback. What matters is whether you are comfortable when you want to be, which you say you are. The human comfortometer on a scale from 0 to 10 is arguably the most important instrument in the whole system, albeit with energy in in kWh not far behind.

I've been thinking of how you might detect cycling if present reasonably easily and without great cost. The clearest and most accessible marker for cycling is the cyclical change in LWT. You could perhaps try adding a RC-4 temperature data logger (~£20) to the primary flow pipe from the heat point at the first point where it becomes accessible. These data loggers usually come with a temperature probe that you could attach to the pipe, and then set the recording interval to once per minute. You then download the data via USB and plot it in any spreadsheet. You could even add a second RC-4 to the return pipe, and, providing you make sure the timelines are in sync, detect defrosts (LWT goes below RWT).     

Posted by: @majordennisbloodnok

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We were both mentioning times we've heard people pointing out the truism that you don't want a warm radiator; you want a warm room.

We cross posted, the real deal is a warm (comfortable) person!

@cathoderay 

Regarding the mobile app, by hovering a finger over the screen I can see detailed data albeit with a sampling rate of 5mins. And given that there has been no other major loads (apart from the occasional kettle) I have yet to discover when/if midea cycles.

Thank you for the idea of sampling LWT. I will look into it!