rad valves, which side of radiator?

[DIYedboy]

Usually the valves are at the bottom on each side, on a 6 foot long rad, will it be less efficient if both valves are fitted on the top and bottom on one end?

 

[Parkymike]

Top and bottom OPPOSITE ends are the most efficient.
Top and bottom SAME ends waste of time.

 

[D_Hailsham]

Top and bottom OPPOSITE ends are the most efficient.
Top and bottom SAME ends waste of time.

If that is so, why does the current British Standard BS EN442 specify Top and Bottom, Same ends as the connection required when testing radiators, with flow connected to the top and return to the bottom?

The usual method, connecting both flow and return at the bottom, actually produces about 2% less heat output.

 

[DIYedboy]

Thanks D Hailsham, I learnt something there, it's always difficult on here to know whether the respondants know what they are talking about....................unless they quote facts!