Radiator Size - Should I go larger then calculators suggest?

[ToastyToes]

Hi all,

Master bedroom calculations suggest a requirement of 5100 BTU.

• 4.7m x 3.6m
• Solid brick walls
  
• 3 external walls
• 2 sash windows

I was planning to get two of these rads:
https://www.directheatingsupplies.co.uk/stelrad-concord-lo-line-144-x-1200-double-radiator-148310

They are 2717 BTU each (only 15cm x 120cm) to put under each bedroom.

Question is:
Should I over spec the radiator and turn them down, or would these be sufficient?

Thanks

 

[johnny2007]

I have the same radiators and if i hadn't gone over spec i would've been cold.
They don't work as well as standard panel radiators, so go with the highest btu you can.

 

[Jackrae]

Classic case of 'form over function'
Ever wondered why large ("ugly") cast iron radiators seemed to work yet modern ("stylish') compact units seem to struggle

 

[ToastyToes]

I have the same radiators and if i hadn't gone over spec i would've been cold.
They don't work as well as standard panel radiators, so go with the highest btu you can.

Thanks for your input. Do you have the same size?

 

[muggles]

I normally go 50% bigger - most radiator calculators (especially ones that use old fashioned BTU rather than modern kW) tend to use flow and return temperatures that are too high for modern systems. Calculate based on 70°C flow / 50°C return for best efficiency

 

[johnny2007]

Thanks for your input. Do you have the same size?

No, i have a 1400mm.
Accordingly to btu i needed a 1000mm but it wouldn't have been enough.
Those radiators get very hot, but the heat output is nowhere near the standard steel panel radiators.