i have a baxi duo tec 40 combo and the rads are getting hot when the hot water is running. The gas man changed the insert in the divertor valve and some other insert behind the gas valve/pump because it was leaking too. The control box on top of the valve has been changed too as it had seized due to water leaking. Even after all this the rads get more heat than the hot water does and it's got us both stumped. What else could be causing it?