Hi. I was hoping to change a radiator in my sitting room for a significantly larger one, but having read a few bits and pieces on the web, I'm not sure whether it is feasible. The existing radiator is a double panel, double fin radiator measuring about 1200 long by about 700 high and is fed by 10mm diameter pipes. I think the output of the existing rad is about 8200BTu / 2400W. I was hoping to replace this with something larger but am now not so sure, due to the diameter of the pipework. Is there a rule of thumb for the maximum size of radiator that can be used in conjunction with 10mm pipes? Would appreciate any advice.