Water pump running?

[A1wil]

Hi, I have noticed after my boiler service, that the pump runs continually,during the hot water schedule. The pump runs even when the cylinder stat is satisfied. The heating engineer is suggesting that it's coincidence " bad timing"that the 3 port vale is now failing. I have tested 3 port valve holding my hand on the pipe work, it heats on either heating,hot water or both when it's asking. The voltage off position for the hot water cylinder stat is 60v, at the nest when the hot water is calling, is that right? . It seems a bit weird that this is all happening just after a service 

[CoolingWizard]

Make sure you measure the voltage as AC voltage at the thermostat. The Nest Thermostat can only handle a maximum of 30 V of AC power. Anything higher will damage the nest thermostat.

Ken, The AC Cooling Wizard 

[A1wil]

Hi, thanks for the comments, I should have put the voltage was at the heat link , not the nest thermostat 

[CoolingWizard]

I am sorry, I did not realize you’re over in the UK somewhere I do not know those heat Link systems, and how to diagnose troubleshoot on install them. We don’t have those in the United States.

Ken, the AC Cooling Wizard