Nest Thermostat 'E', not turning EcoTec Pro off, house like a sauna!

[Pd-legalcbs]

Hi guys, as the title suggests, all other threads seem to be about the 3rd gen nest and not the 'E' version so I've created a new thread.

I believe my old thermostat never worked as the wiring setup didn't match the diagram on the the inside cover which I discovered when installing a new Nest Thermostat 'E'. I could only ever turn the central heating on and then off when it became too warm via the programmer so bought the Nest to save energy.

The nest instructions state the existing programmer needs to remain on. After wiring in the Nest the only way the heating turns off is via the programmer and the nest seems to have zero control.

Ive attached images of all the wiring in both the Valliant Ecotec Pro 28 combi boiler, the nest thermostat E and the programmmer.

The neutral wire from the boiler doesn't appear again in either the programmer or thermostat 'wiring box'. There's also damage to the neutral cable in the boiler and the copper is exposed, possibly why the thermostat never worked?

Can anyone help me or direct me to someone who could help, i've been at this all night? The google nest helpline has been useless. This is also the 2nd heatlink so its not a product fault.

Thanks in advance!

 

[Adam_151]

Can we have a picture of the wiring centre/ heating joint box?

 

[ianmcd]

You need to remove the red link at X100 on the boiler pcb

 

[picasso]

I don't think the pre 2012 models came with a link on the 24v connection, If your original stat did not work its unlikely the nest will, you need to trace the wiring to the stat as I reckon the programmer is wired directly to the boiler.

 

[ericmark]

Reading the instructions it says
Connect the switched live supply with the terminal marked RT at X1 (beside the LNPE connections) then remove the link at X100 (do NOT connect 230 volt to any other terminal than the RT connection).

It also refers to "Observe the flue-gas connection that is required on a room-sealed air/flue gas installation." so would assume this needs doing by some one registered as gas safe?

 

[picasso]

Your looking at the wrong instructions.

 

[CBW]

There’s no link on these older models of pro. Ebus and 20v which says do not use for U.K. shouldn’t really be removing the cover on this boiler as it forms part of the room sealed appliance. Which programmer is it? Your Nest common and NO look both brown cables to me.

 

[ianmcd]

remove the batteries from the nest E , if boiler stays on the fault is at the boiler end, if it goes off the fault is at the nest end

 

[Pd-legalcbs]

There’s no link on these older models of pro. Ebus and 20v which says do not use for U.K. shouldn’t really be removing the cover on this boiler as it forms part of the room sealed appliance. Which programmer is it? Your Nest common and NO look both brown cables to me.

The programmer is a British Gas model UT2. The NO is a grey wire with a brown sheath, as is '3' on the programmer. I should of made that clear on the diagram, apologies.

 

[Pd-legalcbs]

remove the batteries from the nest E , if boiler stays on the fault is at the boiler end, if it goes off the fault is at the nest end

The boiler will be on depending on the programmer. The nest doesnt seem to make any difference.

 

[ianmcd]

The boiler will be on depending on the programmer. The nest doesnt seem to make any difference.

Then the problem is at the boiler end , not the nest end

 

[ianmcd]

why did you post this , there should only be 2 wires in your nest E

 

[Pd-legalcbs]

why did you post this , there should only be 2 wires in your nest E

Behind the old thermostat was them 3 wires in the diagram including an earth. The black wire with a blue sheath and has been capped off (?) as instructed for any wires not in use.

 

[picasso]

Put the programmer back in place, select heating on and see if either of the cables in the nest become live.

 

[Pd-legalcbs]

Put the programmer back in place, select heating on and see if either of the cables in the nest become live.

This has always been the setup. The programmer controls the heating and the nest heat link doesnt do a thing when its supposed to turn the boiler off to regulate the temperature.

The cables to the nest must be live as the circuit wont complete otherwise as the programmer doesnt switch on.