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Heat pumps and on/off working - starting to quantify it

 
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Air Source Heat Pumps (ASHPs)
Last Post by Derek M 2 years ago
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 Derek M
(@derek-m)
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14/10/2023 8:10 pm  

Posted by: @jamespa
↑

Posted by: @derek-m
↑

I have now completed some further improvements to the modelling tool.

It is now possible to adjust the desired IAT setpoint and also the OAT value to one decimal place. This therefore provides the capability to ramp up and down the setpoint and more closely match variations in OAT.

Have fun in the 'Playroom'.

I downloaded your modelling tool but there are lots of '#value' in the playroom.  Is there something I need to dial in to start it working?

Hi James,

Which cells contain '=value'?

 



   
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 JamesPa
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Topic starter 15/10/2023 10:13 am  

About 50% of the play sheet.  I'm guessing they all rely on or derive from one 'problem' cell.

I have an old version of Excel (2003) it could be that, although unlikely because it usually issues a warning if there are unsupported features.  I will try to narrow down the root cause.


4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.


   
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 newhouse87
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15/10/2023 11:04 am  

Had cop of 3.7 for yesterday/this morning, that seems lot better then what i had last winter, 3.04 last winter but that included dhw. Freezing at 5am this morning so running from 530-10-30 had used 27kwh, thats heavy, house now warm, prob too warm so switched off heating and will adjust curve down to 34 at- 5 and 26@20 try that tomorrow. That's a 12 degree difference to installer setting on cold side.



   
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 Derek M
(@derek-m)
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15/10/2023 4:55 pm  

Posted by: @jamespa
↑

About 50% of the play sheet.  I'm guessing they all rely on or derive from one 'problem' cell.

I have an old version of Excel (2003) it could be that, although unlikely because it usually issues a warning if there are unsupported features.  I will try to narrow down the root cause.

Did you resolve the problem? If not, then please provide one cell location and I should be able to trace back to the cause.

I may be able to save the spreadsheet in a different format if that would help.

 



   
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 JamesPa
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Topic starter 16/10/2023 8:35 am  

Unfortunately I didn't resolve it.  #value cells include E1-AA1, D14, 16-18,20,23,24,31,32,36... but

opening it in Libre office calc seems to have fixed the problem.  I will report back if I work out what the problem was!


4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.


   
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 Derek M
(@derek-m)
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16/10/2023 9:23 am  

Posted by: @jamespa
↑

Unfortunately I didn't resolve it.  #value cells include E1-AA1, D14, 16-18,20,23,24,31,32,36... but

opening it in Libre office calc seems to have fixed the problem.  I will report back if I work out what the problem was!

Hi James,

As you will have noticed I carried out quite a number of modifications to create the present version, one of which was to simulate the heat pump stopping and starting. This uses the cells D1 to AA1 to set cells D14 through to AA18 to zero if the heat pump is deemed to have stopped.

The formula in cell D1 sets the cell value bases upon the values of cells D9 (Setpoint Temp.) and D11 (Actual IAT), such that if D11 > D9 + 0.1C the heat pump is switched off, cell D1 set to 0.

Try overwriting the formula in cell D1 with the actual value 1 or 0 and see what effect this may have. You could also try changing the value in cell E9, above and below that of cell E11, to see how that affects the formula in cell E1.

 



   
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 newhouse87
(@newhouse87)
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16/10/2023 6:30 pm  

Hi lads,any idea why my flow temp would be this high when my curve would suggest it should be lower. I have attached pics.

IMG 20231016 WA0001
IMG 20231016 WA0002

 



   
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 JamesPa
(@jamespa)
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Topic starter 16/10/2023 7:59 pm  

Has it just come out of a dhw cycle, which would be at a much higher ft (and thus may take a while to cool down)?


4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.


   
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 Kev M
(@kev-m)
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16/10/2023 8:35 pm  

There might a minimum LWT setting that applies whatever the WC curve says.  Maybe that is 30? 


This post was modified 2 years ago by Kev M

   
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 newhouse87
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16/10/2023 8:43 pm  

@jamespa No DHW cycle is 2-3pm, this was much later. Judging on my curve, @7.2deg, what should flow temp be? Maybe its ok. Using lot less KWH last few days which is good as i have been lowering flow temp since and slab is probably warmed up.



   
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 newhouse87
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16/10/2023 8:53 pm  

Posted by: @kev-m
↑

There might a minimum LWT setting that applies whatever the WC curve says.  Maybe that is 30? 

Have desired temperature on front screen but think that changes with the curve.

 



   
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 JamesPa
(@jamespa)
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Topic starter 16/10/2023 9:04 pm  

@newhouse87 well your WC line is 34 at -5 and 25 at 20,  so at 7 you expect 25+9*(11/25) = 29.  So 30 is just 1C out which is likely well within the hysteresis.  Situation normal so far as I can see 


4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.


   
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