I want to run for he integral pump because the central heating and the engine have independent coils which feed into the chlorifier to supply domestic hot water, ergo whilst cruising I should be able to recover heat from the chlorifier to feed the radiators, I want to avoid fitting an external circulating pump on the radiator system. If I can independently run the integral water pump on the hydronic that would circulate water through the rads and that means I can achieve heat recovery from the chlorifier via the engine whilst cruising.