Nest thermostat

[sadders]

I just want to double check things before I install this.

I have a Vaillant ecotec combi boiler (couldn't tell you which model).

Its wired to a junction box in the hall cupboard. Off the junction box is a drayton heating and hot water timer. A separate 4 core wire goes to a honeywell mechanical thermostat mounted in the hall. The wires are earth, neutral live and switched live.

I presume I leave the timer in place and wire the current thermostat wire to the nest heat link (removing the earth) live to live with a jumper to common, neutral to neutral then switched live to terminal 3 (call for heat). T1 and T2 are low voltage to the thermostat.

Leave the timer control to always on for the heating and hot water timed through the timer as normal.

I presume this will work fine as the timer will always be calling for heat but the thermostat will then control on and off depending on temperature and time (instead of just time as the honeywell T40 currently does).

Does this seem correct?

With thanks as always.

 

[SilentDancer]

Yes sounds like you've got the right idea.

 

[notinventedhere]

sadders, was wondering if you went ahead with the installation as you described (specifically the wiring to the Heat Link) and if the Nest all works correctly? I have the exact same timer/thermostat set up it seems, so would be handy to know if someone's already done the exact same job I was planning!

 

[Doe]

If it helps, i did the same as described with my Tado install. Works fine.

 

[notinventedhere]

I've actually ended up posting a new thread here:
//www.diynot.com/diy/threads/replacing-honeywell-t40-with-nest-thermostat.425422/#3305651
rather than clutter up this thread