does pump operate on baxi 105 he boiler when hot water tap turned on or just when central heating turned on Thanks Barry

barry, January 2015

Yes.

When the hot water tap is turned on, the boiler runs similarly to when the central heating is on, but the gas heated water only circulates around the boiler (via the plate heat exchanger) rather than around the radiators. Cold mains water also enters the boiler and passes through the other side of the plate heat exchanger, and exits the boiler as hot water. The plate heat exchanger keeps the boiler water and mains water separate, but allows the heat to pass from the one to the other.

Anon, January 2015

Pump run when heating on and hot water as well with out pump run and fan run all time boiler will not work

Ltd, January 2015