Yes, you could run several radiators from a log burner with a wetback. If the wetback is currently heating a domestic hot water cylinder, and you wish this to continue also, the cylinder would have to be modified to separate the water going to the radiators from the water going to the cylinder. This is because the rust generated by the water in the steel radiators would infiltrate the potable/drinking water in the cylinder. For a new installation, you can get a cylinder that already has this coil or heat exchanger in it.
