replacing switchmaster programmer

[pw21]

Hi,
Please can anyone advise if its possible to replace a Switchmaster 400 programmer for a more modern digital type controller.
The system is a y plan, with a drayton ma1 three way valve.

The wiring diagram i have for a y plan system shows a hot water off wire coming from the programmer but the switchmaster 400 doesn't seem to have this.

Any advice appreciated as i'm now stuck!

Many thanks

 

[twgas]

You can still change it, slight wiring alteration, iirc, if you set the new prog to "gravity" it will work as your existing one. a HW off would mean you can have heating timed for on when the HW is off.