radiator output differences for same size Rads?

[BertieC]

Is there a reason for a large differnece in output BTU's for radiators of the same style and size? Small differences I get but on a 500mmX1400mm double panel convector radiator the outputs are 6900 btu for a Prorad or 9261 btu for one of the same size and style as supplied by Compass.
Any reason for this? makes it a little confusing when trying to size one for a room.

 

[muggles]

Could be that the Compass ones are (misleadingly) quoted at higher mean water temperatures. The general standard is for the difference between mean water and room temperatures to be taken as 50 ºC, but if they've taken it as 65ºC for example, then the output will be much higher (Stelrad use a conversion factor of 1.406 at mean difference of 65ºC, applying that to your Prorad would make it 6900×1.406=9701 btu).

Just a theory but would explain the difference.

 

[BertieC]

Thanks,
yes that would make sense, shame they are not obliged to use the same calculations when they quote output BTU's then.

Anyway as I said many thanks.