Pump running continuously on unvented system

[cliverlong]

A friend has moved into a house (in UK) which has an unvented heating/hot water system, with an OSO cylinder and a red expansion vessel. Currently the heating is off and we switch on the boiler when she want to heats the water in the cylinder. The cylinder of hot water lasts a few days. Rather than switching on the boiler she has the option to use the immersion heater.

I have printed off the instructions for the heating/hot water controller/timer, but I have yet to work out exactly how to set the controller. The controller is a Danfoss FP715Si.

The system has an external Grundfos pump. Now I know a little bit about vented systems with header tanks. I understood that the pump only comes on when the heating system is on in order to pump water around the heating circuit. However, at the moment the boiler is switched off most of the time but the pump is on continuously. Is this correct? It doesn’t make sense top me. If the pump should be off when the heating is off, how do I switch off the pump so it doesn’t burn out? There isn’t a switched electrical supply to the pump to allow me to switch it off (I guess it should be controlled by the controller).