OK...no replies.....I think I meant "thermo-syphon" rather than "gravity" in my original thread and I may have confused folks.
. Here is a picture of my existing Rayburn system. The pump is in the "Alt" position of the 2 positions shown in the diagram and is currently operated by a simple hand operated on/off switch. What I am trying to ascertain is if the pump was running with the Rayburn cooker extinguished, would it remove heat from the cylinder and therefore usefully act as a heat dump for when I fit my solar system? To do this, the pump would have to induce a flow through the boiler coil and back to the cooker and I'm not sure if the injector Tee would allow this to any useful degree. If it would then I could use the TDC3 to operate the pump during overheat conditions. Hopefully my question is a little clearer and thanks in advance for your views.