How to connect nest heat link to riva compact he mk2?

12 Jan 2023
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United Kingdom

I have recently bought a nest thermostat to replace my Honeywell wired thermostat and i was wondering if someone can help me with instructions on where to connect the heatlink to?
Find attached pictures of the fuses on the boiler, connections on heat link and from boiler.

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The Heat link 'Heating Common' (2) and 'Heating call for Heat' (3) are connected to boiler terminals 3 & 1 as per the manual below. The wires to the existing thermostat are removed.


Then the Heat link also needs a 230V supply to N, L, E to provide it with operating power. That comes from the same 3A fused connection unit that supplies the boiler.


If you are going to use the Heat link to power the Nest thermostat, then a cable to connect the 12v T1 & T2 terminals of the heat link to the T1 & T2 terminals of the Nest thermostat are also required.

You may see some installations that require a link to be made between the Heat link L and 2 terminals. You must not do this. Your boiler uses different voltages for its power and switching circuits. As per the label inside the boiler and the instructions.

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@stem This is such a clear answer. Thank you.

However one more question. can i take power from the boiler Power supply terminal block? And how ? (I am a rookie, so it might be a stupid question but i don't know it;))

The terminals with the orange arrow are the 230V supply. The diagram at the side tells you ;)

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1) cables should be clamped.
2) if the heat link is any distance from boiler may be better to use two cables, one for power and one for control, but you need 5 cores in all boiler to heat link. I personally don't like mixing low and extra low voltage in one cable.
3) Will also need power to the control module/thermostat, this can come from heat link, (three core cable required according to instructions) or from an independent power supply, normally USB.
4) Since the heat link is volt free, it could be power from else where, however it is normally practice to have all central heating devices powered on the same circuit, this is really for when using low voltage (230 volt) control, but setting it up that way means if you change from extra low to low voltage, the conversion is easier. But most boilers have a fuse inside the boiler, so power when using low voltage should come after that fuse to be classed as on the same circuit, using the fuse in the plug or FCU is not really good enough for it to be classed as same circuit, and if it asks for same supply, then most homes only have one supply.

However the easy option which causes not argument is to use Nest e, which does not need a low voltage supply. Just two wires and battery powered.
I definitely want to try and do it myself. I am used to wires but not Electrical ones. (I am an IT)

I will use the current thermostat wiring to connect the thermostat to the heat link. It is just the 230V connection that i am struggling with how to do it.
It sounds like an easy concept: Pull power from the existing wires (In the picture bellow). But I don't really know how to divide 1 electric wire to 2.
Do i cut only the live and run it trough the heat link and then take the neutral back to the boilers live connection? or do i need to divide the wires?
I will try and figure it out and if i am unsuccessful i will get someone to do it for me and learn for the next time.

Thank you all for the help. this is an awesome forum.
Will also need power to the control module/thermostat, this can come from heat link, (three core cable required according to instructions) or from an independent power supply, normally USB.
3 core cable isn't required according to the instructions -
Screenshot_20230112-153814_Adobe Acrobat.jpg

2 core cable is fine for the 12V feed to the thermostat.

However, an earth connection (from the boiler supply/FCU) must be made to the heatlink earth terminal if T1 and T2 are used.
Internally, T1 and the earth terminal are bridged within the heatlink.
Hence, no need for a 3 core cable.
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