Boiler won't output DHW & CH at the same time.

[DP]

O.P., if you have a mid position actuator, you may as well try and use it as it is paid for. Now you know the boiler does not do 'mid position', the orange and grey are the same as your old actuator, and make the switch when the live feed opens the valve fully.

V404

drawing on the right has a microswitch that operates at end of travel and grey makes with orange
Perhaps I am not seeing something, how does grey connect voltage onto orange in left diagram


I would be tempted to fit a two port actuator on the three port body to replicate the operation. I could well be way off the mark on that as I have not looked at the Boiler manual.

 

[picasso]

I dont think the mid position head will work as it is open for hot water when deenergised (port b open) the diverter valve has port a open when deenergised.

 

[Gasguru]

You need to be careful...in the mid-position the motor is stalled by feeding the motor with 1/2 wave rectified 240V (via the diode) and as a result the motor can become slightly magnetised.
To counteract this effect when there is only a DHW demand the orange is fed with 240V...this energises the motor with miniscule AC in order to de-magnetise it (the motor won't turn though).
I'm not sure how easy it is to energise the orange with just the DHW calling.

Either open up the valve and see if you can modify it into a simple diverter or get the proper valve.