Terminals 4 & 6 on heatlink permanently live

[Matt1959]

My water heating is supposed to be scheduled by Nest, but it turns out that the gas boiler is firing up whenever the thermostat attached to the hot water tank senses that the tank is too cold.

When my plumber checked the wiring both terminals 4 & 6 are permanently live.  Does anybody have experience of this fault?

thanks....Matt

[AlexD]

Thanks for reaching out to us here @Matt1959 . I am sorry to hear you are having difficulties with your device and I would be happy to try and assist. 

For starters, is this a new installation or has it been installed and working for some time before you first noticed this behaviour? Was it installed by a Nest Pro or by a professional installer/electrician? 

Additionally, do you happen to see any kind of water drop symbol on the thermostat display, under the set temperature? If you do, grab a quick picture of it and also please take a screenshot from the Nest app of the current hot water schedule so I can see what the expected behaviour would be. 

[Matt1959]

Hi Alex.  This was first installed in February but I've often noticed that the water heating was on when it should not have been - I put that down to the Heat Link not receiving the 'end' signal when the water heating was supposed to turn off.

However.......adjusting the water temperature thermostat that is fixed to the hot water tank showed that a low tank temperature was causing the boiler to fire up whether the schedule was on or off.  My plumber tested the heat link and found that terminals 4 & 6 were both permanently live, whereas only one should be live at any one time.

Cut a long story short - I returned the Nest equipment to the store for replacement and fitted a new one, which appears to function correctly.

Thanks for your help.....Matt

[AlexD]

Thanks for all the information. It's good to hear that you managed to get things back on track. If anything else comes up that you need assistance with, make sure to open up a new thread or reach out on any of our support channels.

I'll go ahead and close this thread. Have a great weekend ahead!