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Newbie: utterly confused with my Mitsubishi Zubadan air source heat pump running on 55C set flow temperature

 
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Air Source Heat Pumps (ASHPs)
Last Post by JamesPa 2 hours ago
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 Sandman1600
(@sandman1600)
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80 kWhs
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Topic starter 14/03/2025 2:16 pm  

@jamespa Ah, really?  Maybe we’re not as well insulated as we thought.

I am definitely going to follow the more logical approach you outlined. Current setup is just me dropping the flow temp after being alarmed at the amount of electricity we’re using.

I tried changing the flow temp to 36 initially and found the thermostats reporting that the temperature was dropping in some rooms so I’ve upped it to 38.  


   
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 davidnolan22
(@davidnolan22)
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240 kWhs
Joined: 2 months ago
Posts: 38
14/03/2025 2:21 pm  

@sandman1600 if your house is 130m2 and you have a 14kw mitshi machine....... I would be staggered if it wasn't oversized. that's 107w/m2. that's a really really poorly insulated house with holes in the windows 


   
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 Sandman1600
(@sandman1600)
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Topic starter 14/03/2025 2:22 pm  

Posted by: @davidnolan22
↑

@sandman1600 

Your problem will be the minimum output of the 14kw heat pump might be not far from your heat loss in cold weather,

I'm sorry to sound thick but what does this mean? 

As for the rest of your advice, thank you. Definitely makes sense that it may take time to warm up the fabric of the house. I’d kind of considered that the concrete floor would take time to heat but yeah, I’d not really considered the whole property absorbing that heat. Thanks. 

 


   
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 Sandman1600
(@sandman1600)
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80 kWhs
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Posts: 17
Topic starter 14/03/2025 2:23 pm  

@davidnolan22 Oh wow. Starting to sweat that we have been sold an inappropriate heat pump.


   
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 JamesPa
(@jamespa)
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10956 kWhs
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14/03/2025 4:55 pm  

Posted by: @sandman1600
↑

@davidnolan22 Oh wow. Starting to sweat that we have been sold an inappropriate heat pump.

Based on the numbers I think its likely its oversized.  Not a disaster but it means it will probably cycle on and off a lot.  If does prove to be oversized (difficult to tell until you have it working without influence from external controls and also some monitoring) and you have a big enough slab you may find you can cost effectively batch heat the slab during cheap rate periods (much like storage heaters).  It may take some experimentation but for sure you are going to save money relative to operating at 55C flow temperature!

 

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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