Nest Thermostat wiring

yoyo

I am looking to replace an old single zone EPH CH Timer with Nest Thermostat shortly. The current thermostat is wired as follows:

In above example Live is looped into COMMON/1 and the ON/CH wire into 4. For the nest I am following the Combi boiler wiring diagram:

Am I correct in saying for the Nest all I need to do is loop live into 2, and the ON/CH wire into 3? There is already a 3A Fused Switched Spur feeding the old timer.

This is a simple single zone setup (CH and HW all the one), no mains fed wall thermostats in the house either so won't be making use of any of the other terminals.

youtheman

Yes, assuming "If mains voltage output is required" as per the first diagram. So check that there is a loop between L and 1 on the existing device. You'll also have to run a pair of cables from T1/T2 to the device, though you can run it in wireless mode and just plug the device is and charge it with a USB cable (like a phone).

yoyo

https://www.boards.ie/discussion/comment/120058624#Comment_120058624

That is great youtheman, thanks! The current timer is under the boiler so I bought the Nest Thermostat stand separately to plug in elsewhere for that reason :) . I will double check mains voltage is required (existence of loop on existing timer) before attempting same I am fairly confident it is switched by mains voltage (Ideal boiler) but will double check this thanks for the hint.