Diode in a link wire for Thermostat?
Not sure if my system is exactly the same, but I have to run the pump and boiler to get HW and the pump, boiler &amp; a valve to get heating. The valve is a simple looking bypass thing with just live, neutral and earth and is sprung return. Now according to NEST such a system isn't compatible. However, I've wired with the live going to 2 and 6 (that's right, not 5) on the heatlink. Along with the valve on 3 and a jumper going from 3 to 4. The boiler and the pump are then on 5. This gives me full heating and independent HW control from the NEST without any relays etc. So far it's working perfectly. I looked for ages to find an answer to this and couldn't find a satisfactory one for my application. I hope this helps someone else in the same frustrating position!