Nest 3rd Gen Wiring Question

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I want my new 3rd Gen. Nest to control both a heating zone and the boiler itself so that I can remotely switch it on/off. The heating is working fine (terminal 3 comes live as the heatlink calls for heat) but terminal 6 on the Heat Link is permanently live and does not switch when selecting Hot Water on/off in the app. I followed the wiring instructions (see photo). Have I got it wrong? Thanks in advance.
 

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You have nothing connected to 3 on the heat link so that's not controlling your heating and nothing connected on six so why would you expect it to control your hot water ? what are you trying to control, combi, zone valves or ?
 
I was just testing my wiring before I installed the heat link and thermostat properly. I was testing terminal 3 and 6 with a phase tester. Terminal 3 will be connected to my heating zone pump and I was intending to connect terminal 6 to the boiler but I was surprised to find that terminal 6 was permanently live regardless of whether the HW was on or off in my App.
 
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Probably just ghost voltage, what type of system do you have , its unusual to control the boiler on/off using the hot water on side of the nest.
 
I have a Grant Vortex Condensing Boiler connected to a Systemlink manifold with 4 heating zones (two of which have Nest thermostats connected). I want the new Nest to control the third heating zone and the HW control in the app to switch the boiler ON/OFF. I want to be able to remotely turn on the boiler/heating. Once the boiler is ON it heats a separate HW cylinder. I was hoping to get some direction on the correct wiring for terminals 4,5 & 6
 
How is the hot water cylinder plumbed in ? is there a separate pump and circuit off the systemlink or plumbed straight off the boiler?
 
How is the hot water cylinder plumbed in ? is there a separate pump and circuit off the systemlink or plumbed straight off the boiler?

It's pumped straight off the boiler to both the CH manifold and the HW cylinder.
 
Probably just ghost voltage, what type of system do you have , its unusual to control the boiler on/off using the hot water on side of the nest.

I decided to connect a light bulb to Terminal 6 and the Neutral terminal and the light only came on when I had the HW schedule set to ON. Your theory about a ghost voltage was correct! Many thanks for that. I'm now good to go. I didn't want to undo the existing system until I was confident the 3rd Gen Nest would work as I hoped. Now I am, so again thanks for your patience. (y)
 

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