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Air Source Heat Pumps (ASHPs)
Last Post by batalto 2 years ago
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 Derek M
(@derek-m)
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Joined: 5 years ago
Posts: 4427
10/11/2021 11:44 am  

@batalto 

The thermostat is set at 21.5 degrees and the house is being held at 21 and has been for over 24 hours.

Good morning Batalto,

Very useful data.

As a check, try increasing your thermostat setpoint to say 23C and see if the indoor temperature increases. If it does then your system is not fully operating on weather compensation.

You could try make the slope of your weather compensation shallower, by changing the left hand end to 50C @ -10C.

Don't change the slope immediately, increase the thermostat setting and wait several hours or more to see the effect.



   
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 batalto
(@batalto)
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Topic starter 10/11/2021 11:49 am  

@kev-m actually I used LESS power. You can see from below the details of the days. 

image

And of course as soon as I said it, I was wrong. My heating got the house to 21.5, so I've adjusted the weather curve down a tiny bit from 25@20, to 25@18. I'll wait to see the impact. Also yesterday I adjusted the hot water from 55 to 53 and that seems to be fine as well. Its not perfect as ambient is an average of the whole day - It could have been a cold night and a warm day and still average 13 vs 13 all day. However for my needs its close enough to be interesting.


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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 batalto
(@batalto)
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Posts: 1091
Topic starter 10/11/2021 11:54 am  

@derek-m It doesnt matter what I set the thermostat to. Originally I had it on 22, but moved it to 21.5 to prevent a boiling house if the experiment went totally wrong. So far my nest app says the heating was being called for "23.5 hours" yesterday. It is showing 21 steady in the house downstairs. I've left upstairs on normal thermostat as its so warm up there anyway its not really ever on. When it does come on, it warms up pretty quickly.


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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 batalto
(@batalto)
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Joined: 4 years ago
Posts: 1091
Topic starter 11/11/2021 12:03 am  

Checked the filter today and it was pretty much totally clean - so I think the gunk is now cleaned out. The system is basically silent now as well, whereas before it made a high pitched noise in the main return pipe. I assume this was just a restricted flow issue.

House seems to be totally fine today, however the temps seem to creep up in the day. Now evening has come it's back to holding at 21. Not sure what to do as it seems to be a solar gain issue. However it wasn't a major issue as it was only 0.5° above target. A stated I've adjusted my curve a little bit. I'll be leaving it alone for the next few days and seeing the impact. However any tweaks will be around the edges.

Current setting 50°@-3° and 25°@18°


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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 batalto
(@batalto)
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Posts: 1091
Topic starter 11/11/2021 12:39 pm  

room temperature hit 21.5 again today, so trimmed the weather comp at the bottom end a little. Its not exactly sunny, so solar gain should be negligible today. Now the house is up to temperature it'll be interesting to see how it holds. slowly slowly dialling in. Just need a cold snap to see how we are really getting on


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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 Kev M
(@kev-m)
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Joined: 5 years ago
Posts: 1276
11/11/2021 2:14 pm  

@batalto,

we're a tiny bit cooler indoors today on the same flow temps.  I think it's because it's damps and misty.  Not enough to worry about though.  Like you say, this is too easy, we need some proper winter weather. 



   
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 batalto
(@batalto)
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Joined: 4 years ago
Posts: 1091
Topic starter 12/11/2021 10:10 am  

Ran through the night with a COP of 4.2 - Lost some heat downstairs though, the temperature dropped to 20. So I've adjusted my curve 1 degree upwards; 25 @ 17

 


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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 Derek M
(@derek-m)
Illustrious Member Member
Joined: 5 years ago
Posts: 4427
12/11/2021 10:17 am  
Posted by: @batalto

Ran through the night with a COP of 4.2 - Lost some heat downstairs though, the temperature dropped to 20. So I've adjusted my curve 1 degree upwards; 25 @ 17

 

Good morning Batalto,

The wind speed was higher last night in our area, and I have noticed that it appears to have added about 5C to the required water flow temperature.



   
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 batalto
(@batalto)
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Joined: 4 years ago
Posts: 1091
Topic starter 12/11/2021 10:28 am  

@derek-m there is a bit of cycling on the system due to the super mild weather (ambient was 13 overnight). However its very wet today, so interesting to see how we get on. The house is well up to temperature now.

image

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


   
ReplyQuote



 Kev M
(@kev-m)
Famed Member Member
Joined: 5 years ago
Posts: 1276
12/11/2021 10:37 am  

@batalto,

The overnight peaks are very similar to mine.  What's the peak between 6 and 9? HW or the curve being moved?



   
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 batalto
(@batalto)
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Joined: 4 years ago
Posts: 1091
Topic starter 12/11/2021 10:44 am  

@kev-m It'll be a mix of hot water (for the showers), my wife's hair dryer, washing machine going on etc. This measures power in 5 min intervals, so its prone to being a bit spikey. You think 2/3kw for hot water being heated plus a 2kw hair drier and you're getting up there. Interestingly I am still running on battery, so my power is still 5p/kw

SOC = State of charge e.g. %

image

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


   
ReplyQuote
 Kev M
(@kev-m)
Famed Member Member
Joined: 5 years ago
Posts: 1276
12/11/2021 11:15 am  

@batalto,

ah I see; you're recording all power, not just the ASHP



   
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