Nest 3rd Gen not sending command to combi boiler

[Drift5475]

Hello,

I have had a Nest 3rd Gen thermostat and heat link connected to my boiler, ATAG ic28, for several months now with no problem.

I tried to change the temperature today and it is seemingly not sending the command to the boiler anymore. I have set the temp via the Nest app and also manually on the thermostat itself and nothing on the boiler happens.


If I manually press the button the heat link, i get the three green lights but again nothing on the boiler fires up.


I am getting hot water from showers and taps with no problem and all the usual checks I can do on the boiler e.g. pressure and so on are all fine.



Have removed the Nest from the nest app, reset the thermostat and held the button on the heatlink for 20s to reset also.

I can see on the nest itself the heat link is showing as being connected "wirelessly" .



Thanks

 

[cross thread]

What heating temperature have you on the boiler display ? When calling for heat do you get a box around the heating temperature display?

 

[Drift5475]

What heating temperature have you on the boiler display ? When calling for heat do you get a box around the heating temperature display?

Central heating temperature is showing as 60c.

When I call for heat, there is nothing on the display. When it used to work, you would hear the click of the boiler after maybe 5seconds of changing the Nest, then the ignition symbol and the boiler would kick in and you would hear it getting up to temperature.

This is link to my boiler manual, https://www.atagheating.co.uk/hubfs/Appliance Technical Guide Pre 2019.pdf

I have no error codes or anything on the boiler itself.

 

[RandomGrinch]

When I call for heat, there is nothing on the display. When it used to work, you would hear the click of the boiler after maybe 5seconds of changing the Nest, then the ignition symbol and the boiler would kick in and you would hear it getting up to temperature.

Assuming your boiler isn't using OpenTherm; To rule out a faulty Heat Link, with the power off, connect the wires in terminals 2 and 3 together.
With the power restored, if the boiler fires, the Heat Link is at fault (and Nest are usually pretty good at replacing them).
If the boiler remains off, the problem lies elsewhere.

 

[Drift5475]

Assuming your boiler isn't using OpenTherm; To rule out a faulty Heat Link, with the power off, connect the wires in terminals 2 and 3 together.
With the power restored, if the boiler fires, the Heat Link is at fault (and Nest are usually pretty good at replacing them).
If the boiler remains off, the problem lies elsewhere.

This is how I currently have it wired up, https://imgbb.com/SxVx1fV

Power off boiler, unscrew cable from terminal 2 and 3, power back on and just tap 2 and 3 together (as if I am hot wiring a car? lol) and see if the boiler fires?

 

[RandomGrinch]

Power off boiler, unscrew cable from terminal 2 and 3, power back on and just tap 2 and 3 together (as if I am hot wiring a car? lol) and see if the boiler fires?

No!
Connect the wires from terminals 2 and 3 together in the same terminal - i.e. both wires connected into terminal 2.
And for safety, put the cover back on the Heat Link, before restoring power.

We don't want to be playing with mains voltages - no hot-wiring involved!

 

[Drift5475]

No!
Connect the wires from terminals 2 and 3 together in the same terminal - i.e. both wires connected into terminal 2.
And for safety, put the cover back on the Heat Link, before restoring power.

We don't want to be playing with mains voltages - no hot-wiring involved!

Ok, so keep the jumper cable from L to 2, put green and white into 2 and then hit the manual button the nest link to get it to fire up?

 

[RandomGrinch]

and then hit the manual button the nest link to get it to fire up?

Not even that - by linking those two wires together, we are completely by-passing the heatlink - you won't have to press anything.
If the Heating comes on, we know the heat link is misbehaving.

 

[Drift5475]

Not even that - by linking those two wires together, we are completely by-passing the heatlink - you won't have to press anything.
If the Heating comes on, we know the heat link is misbehaving.

Ok, so boiler booted back up and it went through its venting program. I can see the radiator on the boiler display is flashing and the ignition flame has appeared. Boiler is firing and radiators getting hot!

 

[RandomGrinch]

Ok, so boiler booted back up and it went through its venting program. I can see the radiator on the boiler display is flashing and the ignition flame has appeared. Boiler is firing and radiators getting hot!

Ok, sounds like the Heat Link is the problem then.
Contact Google and see if you can get a replacement.
In the meantime, use the controls you have on the boiler to turn the C/H on and off.

 

[Drift5475]

Ok, sounds like the Heat Link is the problem then.
Contact Google and see if you can get a replacement.
In the meantime, use the controls you have on the boiler to turn the C/H on and off.

Thanks for helping find the issue. I will contact Google.

I don't think i can just trigger c/h from the boiler itself, unless I am reading the manual wrong?

 

[RandomGrinch]

I don't think i can just trigger c/h from the boiler itself, unless I am reading the manual wrong?

If I've got the correct model, just keep pressing the C/H temp down button until a dash appears in the display?

 

[Drift5475]

If I've got the correct model, just keep pressing the C/H temp down button until a dash appears in the display?

View attachment 347855

I see, thank you.

I have contacted Google and they have asked me to fill this out before they will carry it on further.

1. Ensure the relay switch is in the correct position by checking for continuity with feed Live and Neutral connected but all wires disconnected from the relay itself.
   1. When the Nest thermostat is calling for heat, check for:
      1. Continuity between 2 and 3
         • Yes
         • No
      2. Continuity between 1 and 2
         • Yes
         • No
   2. When the thermostat is satisfied, check for:
      1. Continuity between 2 and 3
         • Yes
         • No
      2. Continuity between 1 and 2
         • Yes
         • No
   3. 
      When the Nest thermostat is calling for hot water, check for:
      1. Continuity between 5 and 6
         • Yes
         • No
      2. Continuity between 4 and 5
         • Yes
         • No
   4. When the thermostat is satisfied, check for:
      1. Continuity between 5 and 6
         • Yes
         • No
      2. Continuity between 4 and 5
         • Yes
         • No
2. 
   Voltage test steps.
   1. High voltage wiring test (wire bridge from L into terminal 2 and 5 for hot water control) when the Nest thermostat is calling for heat or hot water, check for:
      1. Voltage between N and 3/N and 6 for hot water
         • Yes
         • No
      2. Voltage between N and 1/N and 4 for hot water
         • Yes
         • No
   2. When the thermostat is satisfied, check for:
      1. Voltage between N and 3/N and 6 for hot water
         • Yes
         • No
      2. Voltage between N and 1/N and 4 for hot water
         • Yes
         • No
   3. Low voltage wiring test (wire from the boiler into terminal 2) when the Nest thermostat is calling for heat, check for:
      1. Voltage between 2 and 3
         • Yes
         • No
      2. Voltage between 1 and 3
         • Yes
         • No
   4. When the thermostat is satisfied, check for:
      1. Voltage between 2 and 3
         • Yes
         • No
      2. Voltage between 1 and 2
         • Yes
         • No

3. Heat Link status light is as expected when calling for heat, but the heating control circuit is not operating. There is no fault with the Nest Thermostat.

• Check the controls for faults (boiler, heat pump, motorized valve).
• Recheck the wiring connection at Call for Heat Terminal 3 on the Heat Link.
• Recheck the wiring connection on the Call for Heat wire at controls (boiler, heat pump, motorized valve)

I am not even using 4, 5 and 6 so I assume I just skip those but the others I will need to use a multimeter.