Raditor sizing for Vortex condensing boiler

[garyo]

I'm currently sizing the radiators for our new extension. They will be connected up to a two year old Grant Vortex.

For the first room I looked at, a couple of online calculators say that I only need a 600w radiator (the room is a first floor bedroom, 4m by 4m, 1m2 window, insulated to current spec).

I was surprised and due to the size of the wall/window was on auto-pilot and going to fit a 1.2M wide one (double/finned) which would have been 2000W.

I'm happy to size down, but wondered if I should err higher to keep return temperatures down?

Thanks

 

[Agile]

There is nothing technically bad about over sizing a rad. Providing the balance is set up to achieve the flow/return differential required by the system. That is often about 20 C on a condensing boiler. Your boiler needs a return temperature of less than 55C to enable good condensation.

I actually like to over size rads but for a slightly different reason. But not using double panel rads.

Using a long single panel spreads the heat source further and can give a better heat distribution in a room.

But that is rarely done because of the extra cost.

They never really caught on but skirting radiators gave a lovely all room heat distribution!