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Midea ASHP – how to set weather compensation

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(@curlykatie)
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@cathoderay thanks for your reply. This is what I’m a bit confused about. I am able to change the  number on the left front screen (currently at 40), and adjust up and down- So assume this would indicate I am not in weather compensation? The only time I have not been able to change it and I have had the message asking if I want to come out of weather temp set mode, is when I have selected a weather compensation curve from the preset temp screen- see attached! 


   
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cathodeRay
(@cathoderay)
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Posted by: @curlykatie

Which numbers am I looking at on the operation screen which will indicate the actual flow temperature? 

The rather unintuitive LWT/RWT (flow return) temps are in the Operational Parameter pages (x2 for good measure, but you only need to look at the first instance): scroll down to page 4/9 (you have an image above), and TW_O PLATE W-OUTLET TEMP if LWT (flow) and TW_I W-INLET TEMP is RWT (return). They tend to fluctuate all the time, and when you have a defrost cycle they will actually appear to be the wrong way round (LWT cooler than RWT) bit it is correct, because it is defrosting.

What I don't know is where exactly these temps are measured, (the naming suggests very near the compressor/plate) or how accurate they are (+/- 1 degree? +/- 5 degrees?) but they are the best we have without adding third party sensors.  

Midea 14kW (for now...) ASHP heating both building and DHW


   
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(@batalto)
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@curlykatie off the top of my head it's page 8 of operations - water outlet temp. Inlet is the temp back into the pump.

No the front doesn't change. No idea why. It never did on mine when I was using an external thermostat. But it is in weather comp

12kW Midea ASHP - 8.4kw solar - 29kWh batteries
262m2 house in Hampshire
Current weather compensation: 47@-2 and 31@17
My current performance can be found - HERE
Heat pump calculator spreadsheet - HERE


   
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cathodeRay
(@cathoderay)
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Posted by: @curlykatie

This is what I’m a bit confused about. I am able to change the  number on the left front screen (currently at 40), and adjust up and down- So assume this would indicate I am not in weather compensation? The only time I have not been able to change it and I have had the message asking if I want to come out of weather temp set mode, is when I have selected a weather compensation curve from the preset temp screen- see attached! 

The fact you can change the LHS number without getting the you are in weather comp mode message suggests you are indeed not in weather comp mode. When you select Weather Temp Set and ZONE 1 H-MODE HIGH TEMP ON (as you have) it should then give you the 1-9 display which you set to 9 (for 'custom' ie set by you weather comp curve) and then you BACK out to the Front/Home page it should be set... Maybe go though it all again, and see whether the Front page LHS temp is now locked?

 

Midea 14kW (for now...) ASHP heating both building and DHW


   
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(@curlykatie)
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@cathoderay this is the piece of information I was missing! I wondered what curve 9 was!! It seems to be working now- thanks so much!

out of interest, do you know what the zones and low/ high temp modes relate to?

finally, should I  I need to adjust the curve, what’s the best method to do this? Ie. A degree at a time, higher number or lower temp number?

thank you- not sure what I’d do with it all the help from this forum!,


   
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cathodeRay
(@cathoderay)
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Posted by: @curlykatie

out of interest, do you know what the zones and low/ high temp modes relate to?

The zones I am pretty sure are for zoned installations, ie where you have different setting for different zones (which I don't, so I just use zone 1). The high/low temp modes have baffled me too, I wonder whether they are to accommodate rads (high) and UFH (low) mode? It's Midea, its idiosyncratic! 

Posted by: @curlykatie

finally, should I  I need to adjust the curve, what’s the best method to do this? Ie. A degree at a time, higher number or lower temp number?

I make smallish adjustments, usually only one end at a time, and wait hours if not days to see the effect. The actual adjustment depends on what is not as it should be, eg if the house is cool at mild ambients, I might move the warmer ambient right hand end of the curve up say 5 degrees. Setting weather comp curves is an activity that makes watching the paint dry seem positively exciting.

Midea 14kW (for now...) ASHP heating both building and DHW


   
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(@curlykatie)
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@cathoderay thank you… I’ll look forward to watching pump dry then 🤣

Final question (for now!)- I have noticed on the app the ‘TBH’ is this to boost the temp for the DHW in low ambient temperatures or have I misunderstood? It seems to use quite a lot of electricity so just wondering!


   
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cathodeRay
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Posted by: @curlykatie

I have noticed on the app the ‘TBH’ is this to boost the temp for the DHW in low ambient temperatures or have I misunderstood? It seems to use quite a lot of electricity so just wondering!

This is yet another thing designed by Midea to keep you awake at night. I'm pretty sue TBH is 'Tank Backup Heater' an optional immersion heater to back up the heat pump when it is floundering. Most of us don't have a TBH, but the wired controller still thinks we do, so it sends out the messages which get picked up in due course by the app. In effect it is just talking to itself. It is one of the things that makes me wonder how Midea actually calculate their  energy in/energy out figures, which sometimes don't really look convincing, eg the TBH using energy to heat a heater that doesn't exist.

Sometimes I get a small icon on the bottom right hand corner of the front page of the wired controller when it is in DHW mode that looks a bit like a disintegrating magnetic mine. According to the Midea/Freedom manual, this means 'Tank heater is activated'. This rather ambiguous meaning I think means the (non-existent) tank backup heater is activated, not the main heat pump driven heater is activated. It really is not a user friendly display at all.  

Midea 14kW (for now...) ASHP heating both building and DHW


   
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(@curlykatie)
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@cathoderay oh right- thank you. The energy usage on the Midea app is much higher than our actual energy usage on the octopus app so this makes sense!

Please it’s not just me struggling to understand it all!!

thanks again 😊


   
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cathodeRay
(@cathoderay)
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Posted by: @curlykatie

Please it’s not just me struggling to understand it all!!

We all are! That's why I am investigating other ways of getting the data. I think I am right in saying the wired controller sends data to the Midea cloud which the app then downloads and processes. It's possible the data also gets sliced and diced while it is in the cloud. The app itself is a load impenetrable javascript (a programming language). I'm trying three different approaches, firstly getting data locally from the wired controller by wifi (thereby bypassing the Midea cloud and the app) but this is not at all easy because Midea treat your heat pump as if it was a nuclear submarine and impose absurdly complicated cryptography on the data, secondly by doing the same thing using a wired connection to the wired controller (which should avoid all that cryptography) and thirdly by using independent sensors. There are two relevant threads on the forum:

https://renewableheatinghub.co.uk/forums/renewable-heating-air-source-heap-pumps-ashps/connecting-to-midea-msmarthome-using-a-pc

https://renewableheatinghub.co.uk/forums/renewable-heating-air-source-heap-pumps-ashps/a-beginners-guide-to-ashp-monitoring

They get quite technical, only worth reading if you are interested, though the second one does explicitly try to be a beginners guide. 

Midea 14kW (for now...) ASHP heating both building and DHW


   
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(@curlykatie)
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@cathoderay Thanks for this. I am interested in learning as much as possible- I’ll take a look 👍🏻


   
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(@derek-m)
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@curlykatie

Hi Curly,

The displayed LWT is 40C because the WC curve is set to a LWT of 40C at an outside temperature of -2C. Obviously, any outside temperature below -2C will set the LWT at 40C.

I would suggest that you change the WC setting to LWT of 40C at outside temperature of -5C, or even LWT of 42C at outside temperature of -10C.

The important thing is for your home to reach the desired indoor temperature, without it being limited by the WC curve settings.


   
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