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Advice on ball park radiator sizes please

 
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Air Source Heat Pumps (ASHPs)
Last Post by Derek M 2 years ago
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 Rusty
(@rusty)
Estimable Member Member
Joined: 4 years ago
Posts: 51
10/08/2023 2:08 pm  

Posted by: @derek-m
↑

I'm afraid that I do not follow your logic, since heat loss is heat loss and is not dictated by the radiator size or type. Different size or type of radiators will merely require a higher or lower water temperature so that the thermal energy output matches the present heat loss.

Sorry, I obviously didn’t explain that very well, and wrong to boot. As you say, the room/house heat loss is fixed and determined by the fabric and outside temperature, etc. the radiators would then be chosen to provide that output at the desired flow temperature and flow rate, again as you state. I was speculating that the values might be for the standard 50C but without checking the actual radiator specifications and so misled myself on the figures, the Stelrad k3 700x2000 for instance looks like it outputs 5424W at delta-t 50 according to the data sheet, which is considerably higher than the values given. Please ignore my mistaken intrusion.


   
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 marknw
(@marknw)
Active Member Member
Joined: 2 years ago
Posts: 6
Topic starter 17/08/2023 7:05 pm  

Thank you all - so grateful for your advice. 

I went back to the company, and they forwarded my query to another branch (the original person being away for 3 weeks). The person there confirmed there was an error - apparently the original guy had read the wrong column of figures or something... 

So I now have a revised set of sizes, which are much closer to what I anticipated:

Room

Watts required

Suggested radiator

Radiator type

  

 

 

 

 

  

Living room

 

 

 

UFH

Shower room

 

 

 

Kitchen

 

 

 

Dining hall

 

 

 

Hall

 

 

 

Landing (1st floor)

700

600x600

K2

  

Study

1050

600x600

K2

  

Sitting room

1600

600x1000

K2

  

Bed 1

1500

600x1000

K2

  

Bed 2

1600

600x1000

K2

  

Bed 3

1550

600x1000

K2

  

Landing (2nd floor

700

600x600

K2

  

Somewhat different to the originals!


   
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 Derek M
(@derek-m)
Illustrious Member Member
Joined: 4 years ago
Posts: 4427
17/08/2023 7:36 pm  

@marknw

I would suggest that you ask the company to provide a full set of heat loss calculations for your home. Also ask them to clarify what is meant by 'Watts required' in the table, and to confirm their calculated Leaving Water Temperature (LWT) coming from the heat pump.


   
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