What if...

[Steve]

Thermo-syphoning heating is still a part of most solid fuel central heating systems. The systems are designed so that in the event of a power failure whilst the stove is burning hard the boiler doesn't overheat and explode. My previous system would happily heat all the upstairs radiators with no electric pump.

To work well the system needs a big pipe from the boiler to the upstairs circuits and back, mine was 38mm vertically, and 22mm out towards the radiators before stepping down to 15mm for each individual radiator. No thermostatic valves, the system is designed to dump heat in an emergency, to protect the boiler.