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14kW Midea ASHP in an old leaky building

RE: 14kW Midea ASHP in an old leaky building

cathodeRay · 2022-02-28T13:17:41Z

I too have recently (beginning of this February) had a Midea ASHP installed (14kW), in my case in an old leaky building (yes, I know) in Sussex but not on the coast. Most of the rads have been upgraded to K3s. I'm interested in the weather compensation settings too, but for an additional reason beyond economy, getting the maximum number of kWs out of the unit. My installer (who has been very helpful throughout) said he doesn't have much experience of different weather compensation settings beyond Freedom's 55@-2/37@15 setting. I tried contacting Freedom's tech dept and they have been rather unhelpful, to say the least. The reason I want to get the maximum number of kWs out is that the 14kW unit is marginal for the building's heat loss. Elsewhere I came across Midea's technical and engineering data, and have plotted out the unit output at different flow temps (LWTs) and external ambient temps. The chart looks like this: As others have pointed out, it turns out that a nominal 14kW unit is far from a 14kW unit except when it is operating in ideal and warm ambient temp environments, when of course you don't need the maximum output! My idea is that if I set the max LWT to maybe 45 degrees at -2 degrees (instead of 55 degrees) and leave the lower LWT at 37 degrees at 15 degrees, then the heat pump will output 12kW (or more) until it gets very cold outside. With a max LWT of 55 at -2, the output drops to nearer 11kW (pale blue line, 55 on the x-axis), which is below the buildings heat loss of just over 12kW at -2 degrees outside. My questions are: (1) does my proposed way of eeking the maximum output from the unit make theoretical sense (I'm guessing it works something like this: at high flow temps, a bit more power does in, but COP falls sharply, so we get something like (simple made up example) 55 degree flow, 5kW in, COP 2, 10kW out cf 45 degree flow 4kW in, COP 3, 12kW out) and, if the theory is correct, is it likely to work in practice (unlike the economy side of tuning the weather comp settings). I can of course try the settings and see what happens, but with constantly changing ambient conditions it is hard to be sure what actually happens without very close monitoring, and I don't have the kit to do that. (2) if it works theoretically and practically, how - this is really just curiosity - does the unit deliver more kWs to the building at lower flow temps? Perhaps a faster flow rate (l/m) in the primary ASHP to house circuit? Very happy to start a new thread for this, but it also seems to fit here in this currently active thread, so have posted here for now. cathodeRay

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cathodeRay

(@cathoderay)

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Topic starter 05/03/2022 12:52 pm

@batalto - I may be embracing some modern tech with an ASHP but in other ways I am a Luddite - I don't have a smartphone! But shouldn't the data available on the Midea Controller Operation Parameter pages be the same as that which appears on the app? That's where the figures I posted above came from.

I do have wifi in the house, but that is connected to a PC, and installing apps on a PC is a PITA, so it is a pity there isn't PC software that can connect to the Midea Controller/interface, if there is more data available that way.

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

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batalto

(@batalto)

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05/03/2022 1:04 pm

@cathoderay you could get an Android emulator and just install the app on that. Otherwise I don't think there is a way

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

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Topic starter 05/03/2022 1:14 pm

@batalto - I tried an emulator once and it was a right royal PITA. But will the app give me anything I can't get directly from the Midea Controller??? It seems unlikely. If it does, I do have an Icarus Illumina, but it only has Android v4, and it looks like the app needs v5.

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

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batalto

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05/03/2022 2:06 pm

@cathoderay I did take a video of the app, but apparently I can't upload MP4.

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cathodeRay

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Topic starter 05/03/2022 2:31 pm

@batalto - oh well, but thanks very much for trying. If you eyeball what you can see on the app, and what you can see on the Midea controller on the Operation Parameter pages, can you see any obvious differences (if that's not too much to much to ask)?

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

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batalto

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05/03/2022 2:55 pm

@cathoderay you can see way more on the app. You get daily data on power used, generated heat etc

You can also control the unit, adjust temperatures and look back at weekly/monthly stats

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cathodeRay

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Topic starter 05/03/2022 3:05 pm

@batalto - thanks. That sounds like it's worth making the effort for, I'll see what I can do. In the meantime, if anyone (@grahamh, I think it was you who said in one of your Freedom videos that you can use the controller data to determine current COP) can throw any light on what the controller data reported above shows/means, that would be much appreciated.

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

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Graham Hendra

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05/03/2022 7:34 pm

i would advise using the midea app from freedom, its very impressive, give them a call im sure its not very expensive and you can fit it really easily. the actual proper midea app is ok but it has much lower visibility than the freedom version. im sue they will send you avideo or some blurb on it. Im sorry im not an expert on it anymore. I have a red at home, on a red everything is simple it should be for the money.

Heat pump builder

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batalto

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05/03/2022 8:07 pm

@grahamh they are literally the same app, just reskinned. I've tried them both, I prefer the actual midea app as they respond to technical support and bug fixes if you submit them

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Mookyfoo

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05/03/2022 10:08 pm

@batalto I believe they have an app developed by Freedom that they consider is for the installers, forgotten the name of it but its not on the app store you have to get it from them and I was told it was £100 and that they were doing some changes to it so wouldnt be available for a few weeks (this was probably 3-4 weeks ago). I think my installer has applied for it for me. Its meant to give COP and other detailed info and you can send reports back to Freedom if there any problems with your ASHP.

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Mookyfoo

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05/03/2022 10:11 pm

Think it was called MiCloud or Mycloud, but you can only get it from the direct or through your installer.

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cathodeRay

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Topic starter 06/03/2022 10:25 am

£100 seems rather steep for software that in a sane world would come bundled with hardware that costs several thousand pounds!

@grahamh - I wonder if you could comment on what's showing on my Midea controller? Specifically the capacity (output), power consumption and compressor current figures eg at one moment the figures were:

Heat pump capacity: 7.44kW

Power consumption: 1024kWh (kW hours)

Compressor current: 10A

They don't really make any sense, eg 10A = 2.4kW at 240 volts, but the stated capacity (output) is 7.44kW, and the COP (capacity divided by consumption) is whopping 7.3 which is great news - were it not for the fact I don't believe it!

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

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