BAXI COMBI 105E EXTERNAL TIMER

[hlpm]

I HAVE A BAXI COMBI 105E BOILER.
THE BOILER HAS AN INTEGRAL ELECTRO-MECHANICAL TIMER.
I WOULD LIKE TO FIT AN EXTERNAL TIMER INSTEAD.
CAN ANYONE RECOMMEND A COMPATIBLE TIMER AND PROVIDE ME WITH INSTRUCTIONS?
THE INSTALLATION INSTRUCTIONS FOR THE BOILER SHOW THE MAINS INPUT TERMINAL BLOCK HAS TWO EXTRA CONNECTIONS TO CONNECT AN EXTERNAL CONTROLLER.
HOWEVER-THE WIRING DIAGRAM SHOWS A FOUR TERMINAL BLOCK MARKED A3 CONNECTING TO OPTIONAL TIMERS.
I AM CONFUSED AS TO WHETHER I REQUIRE A TIMER USING TWO TERMINALS OR FOUR TERMINALS.
I ONLY WANT TO FIT A PROGRAMMABLE TIMER -NO ROOM THERMOSTATS.

 

[kevplumb]

WHAT

 

[twgas]

WHAT

no need to shout.