Nest hest link lights green but no heating coming on

[Jdonyx]

I have a Worcester Heatslave 15/19 boiler that had a thermostat already connected up which turned the heating on or off rather than setting specific temperatures.

The thermostat has the following wires connected into the circuit: Live, neutral, heating on and earth. It also had a jumper cable.

Trying to install our nest we connected the live and neutral wires appropriately and then the earth wire to the earth port and the last wire to port 3 (heating on) but didnt install the jumper cable to the common wire port due to the forums saying it isnt needed.

The heat link has all lights green and the thermostat says everything is working fine but the heating doesnt seem to be coming on at all.

Is this a case of needing the common jumper cable or is there another glaringly obvious solution that i cant see?

[Raheemthesolwer · Accepted solution]

It's possible that the missing jumper cable is preventing your Nest thermostat from properly controlling your Worcester Heatslave boiler. Here's why:

1. Common Wire: Most boilers require a common wire (sometimes called the C-wire) to power the thermostat and allow it to communicate with the boiler.
2. Jumper Cable: In some situations, the thermostat can steal power from the heating wire (port 3) to operate. This is where the jumper cable comes in. It connects the heating wire (port 3) to the common wire port, providing the necessary power.

However, this setup may not work in all cases, especially with older boilers that require a dedicated common wire for communication.

Here's what you can try:

1. Install the jumper cable:

• Locate the common wire port on your Nest thermostat and the heating wire port (port 3).
• Use a compatible jumper cable to connect these two ports.
• Turn off and on the power for both the thermostat and boiler.
• Check if the heating turns on.

2. Verify wiring connections:

• Double-check that all the wires are connected correctly to the Nest thermostat and boiler terminals.
• Refer to the installation manuals for both the Nest thermostat and your specific Worcester Heatslave boiler model.
• Ensure the wires are securely tightened in the terminals.

3. Contact Nest support:

• If you've tried the above steps and the heating still doesn't work, contact Nest support for further assistance.
• They can help you troubleshoot the issue and confirm if the missing jumper cable is the root cause.

Additional tips:

• Make sure the Nest thermostat is set to heat and the target temperature is higher than the current room temperature.
• Check if the boiler is turned on and there are no error codes displayed.
• If your boiler has a timer or schedule, make sure it's not interfering with the Nest thermostat's control.

It's important to note that I cannot provide definitive advice without seeing the specific wiring configuration and your boiler model. However, trying the above steps, especially installing the jumper cable, should help you resolve the issue.

Remember: Always ensure your safety and consult a qualified electrician if you are unsure about any electrical connections.

[Frustratedddd]

Sounds like the jumper is needed from terminal ''2 to Live''

By having just one wire in the terminal 3, you have no supply to switch the relay. Fit the link.

[AlexD]

Thank you for all the information provided @Jdonyx . I would be happy to try and assist. 

Thank you for the suggestions @Raheemthesolwer and @Frustratedddd . Always appreciated. 

Would you be able to take a picture of the wiring on the Heat Link side, if you are comfortable in doing so? That way I can see what has been done and see if anything stands out. 

You may see mentions on the forum for different wiring. just make sure that you check posts for the EU version of the thermostat as the US one is different. It's possible that the situation is like @Frustratedddd mentioned and you need a wire from Live to terminal 2 on the Heat Link. But we should be able to get a clear picture with a picture of the current wiring. 

[Jdonyx]

Hi everyone, thanks for all the replies! Just to update on this that we added in the Jumper wire between the live and port 2 and the Nest now controls the boiler as intended so this Issue is solved! Thanks for all the help.

[AlexD]

That's great to hear! Make sure to test all the functions but it seems that everything is on track now. Let us know here or reach out on any of our support channels if anything comes up. Have a great week ahead!