Another nest installation

[Alex Green]

Hi everyone,

Thought i would ask for a little help with my nest installation. I thought i would be able to sort it without any issues but then i opened my programmer...

My programmer is a honeywell st9400c. It seems to have 3 wires into the live and 3 wires into the neutral. Nothing in 1 & 2 then a single wire in 3 & 4.

I have a wired honeywell thermostat in the hall which has 3 wires, 1 each in 1,2,3

I'm just not sure which wires need to go where, i tried the 2 power wires into l&n and the 2 remaining cables that were in l&n into t1&2 with the single cable for hw and ch into 3&6.

Obviously this is completely wrong but if anyone could help me out I'd be really greatful

Thanks

 

[Tay7]

Photos

 

[OwainDIYer]

Live - Nest L, 2 and 5 - L you will need to link L to 2 and 5 on the Nest.
Neutral - Nest N - N

Heating call for heat - Nest 3 - Honeywell 4
Hotwater call for heat - Nest 6 - Honeywell 3

That takes care of the Nest Heat Unit. You may have to link a couple of terminals in the thermostat. Usually 1 and 3, and disconnect 2 which is connected to neutral. This takes the accellerator heater out of circuit. Do NOT connect the Nest Thermostat to these wires. You will have to power the Nest Thermiostat from the plug-in power supply.

http://www.honeywelluk.com/documents/Installation-Guide/pdf/835.pdf

 

[OwainDIYer]

the 2 remaining cables that were in l&n into t1&2

Oh dear. That may have rammed 240 volt mains up its 12 volt little bottom, and killed it.

 

[Alex Green]

Ahhhhhh okie doke, so the thermostat cables that were plugged into the l&n should i just tape those up?

And the 3 cables inside the old thermostat just take out number 2 but leave the other?

Thanks

 

[Agile]

And to think that instead of risking damaging it yourself you could have called a Nest professional installer to do it for you!

Tony

 

[OwainDIYer]

Ahhhhhh okie doke, so the thermostat cables that were plugged into the l&n should i just tape those up?

If you know which are the wires to the thermostat then remove them completely from the existing connections. You can then use them for the Nest Thermostat if you want.