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Icy cold weather, weather compensation and consumption

 
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Air Source Heat Pumps (ASHPs)
Last Post by HughF 2 years ago
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Abernyte
 Abernyte
(@abernyte)
Reputable Member Member
Joined: 3 years ago
Posts: 260
02/12/2023 10:08 am  

Fairly similar results here in the Perthshire riviera where we only got to OAT of -7C overnight and recovered a bit to -5C at present. Set back to IAT of 15C  between 2200 and 0600 and I was expecting carnage this morning. IAT had fallen to 17C and the house was recovered to 18.5C by 0800 which was a pleasant surprise. It is currently chewing through 4Kw/h with a fair bit of icing but very few defrosts so far.  Flow temps have been up during recovery and currently 37C with a DT of 5C.

Edit to include.... I was under the impression that the literature says that by -7C the 14Kw Ecodan should be running out of road  and require external assistance to heat adequately. This does not seem to be happening..yet and it seems to have plenty to spare apart from throwing pound notes at the meter.  I can't find where I read or imagined that statistic so I might be wrong.



   
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 Drew Pa
(@drew-pa)
Estimable Member Member
Joined: 4 years ago
Posts: 73
02/12/2023 10:45 am  
IMG 4268

dunlorn/abernyte I think we are not to far geographically apart so it’s interesting to see how everyone’s getting on.  We’ve had -5 and it’s still -4.4c at the moment. Here’s our readings for today so far.  Haven’t seen our efficiency that low since last winter.  

21c down stairs 19c upstairs.  



   
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Abernyte
 Abernyte
(@abernyte)
Reputable Member Member
Joined: 3 years ago
Posts: 260
02/12/2023 11:12 am  

Looks like full recovery of IAT by around 0930 to 20C.  Flow temp is 36C, still pulling around 4Kw/h so I am calling that a success. I haven't seen or at least noticed the predicted high energy usage by using set back overnight.  Defrosts seem to be coming around 1 per 90 mins.



   
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Morgan
 Morgan
(@morgan)
Noble Member Member
Joined: 5 years ago
Posts: 698
02/12/2023 11:56 am  

And the consumption just keeps on rising! 😖 

Screenshot (50)
Screenshot (51)
Screenshot (52)

Retrofitted 11.2kw Mitsubishi Ecodan to new radiators commissioned November 2021.
14 x 500w Monocrystalline solar panels.

2 ESS Smile G3 10.1 batteries.
ESS Smile G3 5kw inverter.


   
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 Kenneth
(@kenneth)
New Member Member
Joined: 2 years ago
Posts: 6
02/12/2023 12:16 pm  

@gary One other question re the 5kw ecodan. What’s the minimum flow rate that’s allowed? There is a graph on the installer handbook but I’m not sure I’m reading it correctly. 
kenneth



   
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 Gary
(@gary)
Reputable Member Member
Joined: 3 years ago
Posts: 350
02/12/2023 12:28 pm  

There is a table with max and min in the handbook for each ecodan size.

this is altered under settings pump speed menu it can be altered from 1-5.  Then if you go to ruining information and put in code 540 it will till you the actual flow rate on litres per min



   
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 Kenneth
(@kenneth)
New Member Member
Joined: 2 years ago
Posts: 6
02/12/2023 12:38 pm  

@gary

IMG 6899

Thanks -found it



   
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 Derek M
(@derek-m)
Illustrious Member Member
Joined: 5 years ago
Posts: 4425
02/12/2023 1:27 pm  

Posted by: @dunlorn
↑

-10°C here overnight and still currently. House is just about at 18°C, so comfortable, but we've pulled 41kWh so far today. 😱

The one noteworthy thing, apart from eye-watering consumption, is that defrost frequency has been only around every 80-90 mins which has allowed the LWT to reach set point. Presumably this is a function of humidity - at around 0°-2°C with damp air or snow falling the defrost frequency can be every 30-40 mins so the LWT never really builds to its target. 

Thank you Dunlorn, you appear to have answered the question I was going to pose to forum members. "Does the defrost frequency reduce at OAT's below -3C?". I read somewhere recently that within the OAT range -3C to +3C, defrost cycling is likely to be at a peak.

 



   
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 Derek M
(@derek-m)
Illustrious Member Member
Joined: 5 years ago
Posts: 4425
02/12/2023 1:37 pm  

Posted by: @abernyte
↑

Fairly similar results here in the Perthshire riviera where we only got to OAT of -7C overnight and recovered a bit to -5C at present. Set back to IAT of 15C  between 2200 and 0600 and I was expecting carnage this morning. IAT had fallen to 17C and the house was recovered to 18.5C by 0800 which was a pleasant surprise. It is currently chewing through 4Kw/h with a fair bit of icing but very few defrosts so far.  Flow temps have been up during recovery and currently 37C with a DT of 5C.

Edit to include.... I was under the impression that the literature says that by -7C the 14Kw Ecodan should be running out of road  and require external assistance to heat adequately. This does not seem to be happening..yet and it seems to have plenty to spare apart from throwing pound notes at the meter.  I can't find where I read or imagined that statistic so I might be wrong.

You are in the fortunate position of having an Ecodan and a well insulated home.

Looking at the manufacturer's data tables, a 14kW Ecodan should still be able to push out up to approximately 15.6kW of thermal energy at a LWT of 37C.

 



   
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Morgan
 Morgan
(@morgan)
Noble Member Member
Joined: 5 years ago
Posts: 698
03/12/2023 9:08 am  

Consumption still increasing.  How do people in really cold countries such as Scandinavia cope with/afford this each winter?

Screenshot (53)
Screenshot (54)

Retrofitted 11.2kw Mitsubishi Ecodan to new radiators commissioned November 2021.
14 x 500w Monocrystalline solar panels.

2 ESS Smile G3 10.1 batteries.
ESS Smile G3 5kw inverter.


   
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 Gary
(@gary)
Reputable Member Member
Joined: 3 years ago
Posts: 350
03/12/2023 9:30 am  

They have well built houses rather than the open barns we have and relatively cheap electricity.  I had an air tightness test performed on my house that was built in 2003 it changes its air 7 times an hour and the tester said that was pretty good for a 20 year old house!



   
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 Bob77
(@bob77)
Trusted Member Member
Joined: 3 years ago
Posts: 36
03/12/2023 12:58 pm  

Yesterday it stayed below zero all day and was foggy - bad conditions for icing. 

My usage for the whole day was 52 kWh or which the heat pump accounted for 33. 

House was always warm, flow temp was 43-44C (I bumped it up a couple of degrees from the WC curve). 

117 square metre 1960s house. A few years ago with electric storage heating I was regularly using 65-70 kWh per day in cold weather - and the house was only 83 square metres back then!



   
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