I think Ric was really getting at Was that to do an NVQ you should really have had some hands on experience already. Was it a shorter course you did rather than apprenticeship
Not really, I was getting at the fact that sizing systems is in the NVQ3 book and that the question seems very vague. Obviously if the question had been more specific such as which brand of radiator has a bigger output per sq m of suface or litre of water content, I would have said nothing. In fairness to the OP, manufacturers come out with an awful load of dribble about radiator 'efficiency' which, in the case of QRL, came down to output per kg of steel in the radiator, so I can see the scope for the question.
FWIW, I have yet to see anything to conflict with my view that all radiators are equally 'efficient' in that they all transfer heat from water to air. Obviously some radiators have better heat transfer for their size, but this will show in the manufacturer's data and radiators would be selected against the heating requirement of the room. Lower water content will mean that once the heating is switched off then there is less potential for overshoot of the required room temperature, but, where the heat output is required more or less constantly, a 1kW radiator is much like any other 1kW radiator.
As the OP will be more aware than me, there is a good argument in favour of fitting higher output radiators and then running the system at a lower temperature, to ensure the boiler runs in condensing mode.
In any case, Tony, welcome to the forums.
