If you want to check it's the right way round, disconnect the valve
completely from the junction box but leave everything else connected. Run
the system in the HW only mode. Hot water from the boiler should circulate
through the heating coil in the cylinder but not through the radiators. If
the radiators get hot but the heating coil doesn't, the valve is the wrong
way round!


Will try that tomorrow.
Will it took a bit longer then planned...

The system is now running without the valve wiring connected, and BOTH
sides of the valve appear to be getting hot - some of this could be
conduction from the feed from the boiler, but I don't think so!

Where now?

Cheers,


Matt