Owning your own home

The only connection I have from the heat link to boiler is the call for heat signal.

Is your 12v power supply to the thermostat provided by the boiler? If so, this could be disconnected and connected to the heat link to provide the 5v power required by the nest.

I have a Worcester Bosch 30 CDI, looking at the wiring template here: http://www.plumbcenter.co.uk/wcsstore7.00.417.75/ExtendedSitesCatalogAssetStore/images/products/AssetPush/DTP_AssetPushHighRes/std.lang.all/ti/on/Worcester_GstarCDi_Pt1_Installation.pdf

Page 31 is the one of interest, and connector ST10 is the one to look at - it goes to the 230v thermostat and programmer.

To my eye I need to connect that terminal block to the Heat Link, and then the Heat Link to the Nest 'stat, unless I plug that in elsewhere.

What I'd like to do now is clarify what equates to what.

On the Heat Link I have:

-Live
-Neutral

I know what they are, but then we have:

1. Satisfied
   
2. Common
   
3. Call for heat
   
   

I think that that maps to/means:

1. I don't know this one - any ideas?
   
2. Live
   
3. Switched Live
   
   

Then on the ST10 I have:

• Live
  
• Neutral
  
• Neutral Switched
  
• Live Switched
  
• Live Return
  
  

Now we can take out the top two, it's the three below (NS, LS, LR) that I need.

Live Switched to Call for Heat makes sense - but what about the Live Return and Neutral Switched?

Finally, looking at the current Thermostat, it connects Live Switched to Live Return, which suggests that Live Return might map to Call for Heat, and the Live Switched to Common?