Nest switches off power to combi bolier

[red_squirrel]

I have a combi boiler with hot water on demand and thought the Nest Learning Thermostat was compatible.  Having wired it up as per the combi boiler wiring diagram it turns the boiler off when heating is not required which prevents the boiler from heating water. The heatlink cuts the power to the boiler at the switch port 2-3.

If I am missing something here please someone enlighten me as I can't see how this can work to allow the boiler to heat water on demand when the way the heatlink controls the heating is by cutting the power source when the heating is not being used.

I previously had a standard wired heating thermostat working fine with this boiler.

[DragosC]

Hi there @red_squirrel

Thanks for reaching out. No worries. Help's here. Could you tell us please when did the situation start occurring first and when was the thermostat installed? Very good issue description by the way, it's very helpful. Thank you. 
 

[red_squirrel]

Hi, thanks for your response.

I'm not sure why that info is relevant but it was installed last week and the situation was immediate.

[DragosC]

We're asking in order to see if the issue is from installation or it occurred after some time. Thanks for your answer. The hot water function of the combi boiler is not thermostat-controlled, so it shouldn't be the case here. The live and neutral terminals from the Heat Link should be wired from the mains, not from the boiler, as for the terminal number 2, it will need a loop/bridge from Live terminal. In terminal number 3 should be wired the signal link from the motorized valve, not the boiler's power wire, in this case, only the heating is controlled by the thermostat, and the hot water is controlled by the boiler and has nothing to do with the thermostat. If indeed the wire number 3 is the one from the motorized valve, it results in a boiler malfunction and that is not covered by the thermostat. 

[george_t]

Hi @red_squirrel. Just checking in, is there anything else we can assist you with at the moment?

[CristianC]

Hey there. I haven't seen any updates in a while so I'm going to lock this thread. If you're still experiencing issues, feel free to open a new one.