Remember, for a gravity fed system all pipework & tanks must be higher than stove & the gravity feed pipe must rise continusly from stove to vent.
Heat leak- where's the heat going to disperse once all your system is piping hot? Meltdown!!! On a domestic system this would be an unvalved large raditor.
Electronic override- a thermostat controlled pump which would click on to disperse the heat once the system is getting too hot. If the pump or power fails this is where the heat-leak is a back-up.
Vent- not a flue but a vented pipe system.
