At someone's house today they had a pump in the airing cupboard, connected - as far as I can tell - to the central heating system. The heating is provided by a boiler in the chimney (I think it's called a "back boiler").
There's a separate switch for the pump - it can be switched off (though I think it switches off anyway when the central heating is off).
What would happen if the central heating were on and the pump were off? Anything bad?
Daniele