Wiring CH controls

[Will]

I have a Potterton Performa 28i combi boiler.

At present the timer is a fixed mechanical type and I do not have a room thermostat fitted.

I want to install a Drayton Digistat 1 Thermostat (battery operated) and a Drayton Tempus 1 timer (mains operated). I need some clarification on the wiring.

There are 2 connections from the boiler pcb (1 and 2). However there are 3 connections on the Digistat. I assume I connect terminal 1 from the pcb to the com terminal (1) on the Digistat. Terminal 3 (call) on the Digistat to terminal 1 (com) on the Tempus. Then terminal 3 (on) from the Tempus back to terminal 2 on the pcb. Is this correct. I have a seperate feed, live and neutral into the Tempus 1.

[Roger Mills (aka Set Square)]

Why not use a programmable stat - and thus do timing and temperature control in a single unit?

I don't quite follow your wiring question, but you almost certainly only need to use 2 of the 3 terminals on the stat - common, plus whichever other one is connected to common when heating is required (and disconnected when the set temperature is achieved). The third terminal would be used *instead* if you were controlling cooling (air-con etc.) rather than heating equipment.