Central heating, pump over-run?

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Just getting used to a more modern heating system.

My older system was a traditional open vent semi-pumped system with just the central heating side being pumped.

When turning the thermostat, as soon as it clicks on, the pump starts and as soon as it clicks off, the pump would stop.

This modern system has a 3 way valve and is fully pumped. But, the thermostat seems to have less immediate effect on the pump. If the thermostat clicks off, the pump still seems to run for a long while. So I can't determine if the thermostat is having a direct impact.

Should I expect an immediate stop/start of the pump? Or is there some kind of over-run built in.

Thanks.
 
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Many modern boilers control the pump directly and incorporate a pump overrun to prevent the heat exchanger from overheating after the burner has shut down.
 
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