How do you wire Nest to Vaillant Combi Boiler?

[RandomGrinch]

I removed the wire (link) between the 24V RT connector and still nothing

Ok, now keep the 24V link removed and as @Taylortwocities suggests,

Put a link in the RT connector and check the boiler then fires

If that doesn't work, show us a picture of the boiler controls on the front panel.

 

[RandomGrinch]

This vid shows how its supposed to be done.
I got motion sickness watching this...

I'm afraid that really isn't the way it's supposed to be done!
The OP has done a far better job.

Brown to N, Blue to L...

Not using cable grips...

 

[Mr Sparkle]

I'm afraid that really isn't the way it's supposed to be done!
The OP has done a far better job.
Brown to N, Blue to L...
Not using cable grip

Many thanks

If that doesn't work, show us a picture of the boiler controls on the front panel.

Attached below.

 

[RandomGrinch]

Many thanks


Attached below.

There's no built in wireless receiver, which could complicate matters, so that's good.
But everything else looks as if it should work, with the heating set to permanently on.

Did you check the heating was working before you attempted to fit the Nest?
Does the boiler fire for hot water?

Next, I would try a link between 230V RT and the terminal next to it - with and without the 24V RT link...

Edit:
Looking closely at your panel photo, the display does say "off". Have you been turning the boiler back on, after you have changed the wiring?

 

[Mr Sparkle]

Did you check the heating was working before you attempted to fit the Nest?

Heating was working perfectly.

When the heating is turned on via the boiler itself, the boiler fires up

However, I cannot control the Central Heating via the Nest Thermostat

Does the boiler fire for hot water?

Yes, it does

Next, I would try a link between 230V RT and the terminal next to it - with and without the 24V RT link...

Attached image below and still nothing

Edit:
Looking closely at your panel photo, the display does say "off". Have you been turning the boiler back on, after you have changed the wiring?

Yes, I have.

You have an excellent eye for detail.

 

[RandomGrinch]

Heating was working perfectly.

When the heating is turned on via the boiler itself, the boiler fires up

This is getting strange.
Did you remove any link wires before you wired up the Nest?
Can you put everything back exactly how it was, and see if the heating now works.

 

[Mr Sparkle]

Did you remove any link wires before you wired up the Nest?

No, I did not.

Can you put everything back exactly how it was, and see if the heating now works.

I have just done that ie grey wire is in RT

RT next to B Off has red cable linked again

Boiler fires up when Central heating is switched on manually at the boiler. However, unable to control central heating via Nest App

Thanks for all the help.

 

[RandomGrinch]

Boiler fires up when Central heating is switched on manually at the boiler. However, unable to control central heating via Nest App

I was afraid of this, and I apologise if there has been a misunderstanding.
Our troubleshooting advice was aiming to find out if the boiler would fire at all - ignoring the Nest completely.
If you have been answering our questions based on the Nest still not firing the boiler, then we may have been talking at cross purposes!

If this is the case, then can we try starting again.
Ignoring the Nest, and with the 24V RT link in place and a link between L and 230V RT does the boiler fire for heating when you turn it on manually?
If you then disconnect the link between L and 230V RT, does the boiler not fire when you turn it on manually?

 

[stem]

Just wondering about the switch below:

Boiler fires up when Central heating is switched on manually at the boiler.

Boilers work differently, so I may not be understating how yours is configured, but I would expect that when you say "switched on Manually" that is using the switch above. So I suspect at this point control should still be going via the Nest. [The difference between the 'On' and the 'clock' is only that 'On' takes the inbuilt clock out of service] So I believe 'On' may be where it should stay and then the Nest should control the boiler.

Alternatively you could use the clock position, but the little tappets on the clock should set to be permanently on 24/7. Otherwise when the clock was off it would stop the Nest controlling the boiler.

I know it's obvious but with the switch in the 'Off' position that would prevent the boiler operating at all.

 

[RandomGrinch]

I know it's obvious but with the switch in the 'Off' position that would prevent the boiler operating at all.

The boiler also has an "On" switch - without pressing that, the display will still operate and show the "off" state shown in the photo.
This is where there has possibly been confusion.
The OP may be expecting the Nest to be able to switch the boiler from "off" to on, when the boiler needs to be on in the first place - that's how I interpret this...

Boiler fires up when Central heating is switched on manually at the boiler.

But again, I may be mistaken.

 

[Mr Sparkle]

1. Do you want me to remove the wire which goes from the heatlink to the boiler or should I keep this in place?

place and a link between L and 230V RT does the boiler fire for heating when you turn it on manually?
If you then disconnect the link between L and 230V RT, does the boiler not fire when you turn it on manually?

2. Using the image below, do you want me to run a single piece of brown cable between the L terminal and RT?

 

[RandomGrinch]

So we're not wasting any more of each others time, I will try and explain what we want to achieve.
With the boiler on and showing the standard display...

And with the heating control knob set to on; we are then looking at which link will make the heating turn off and on.
This will tell us which terminals we need to connect the heat link to.

If I understand you correctly, every time you have turned the boiler on (giving the above display), the heating has come on, irrespective of the state of the Heat link.

You also say that you haven't removed any links within the boiler, before wiring in the Heat link - this suggests to me that the 24V RT link has been bridging the circuit so far.

If that makes sense -
I would remove all wires from the 230V RT terminals. (I.e. safely isolate the grey wire).
I would remove the 24V RT link.
And then, with the boiler turned on, (showing the standard display; with the heating control knob set to on), I would really hope that the heating didn't come on.

Please let me know if that makes sense.

 

[Mr Sparkle]

If I understand you correctly, every time you have turned the boiler on (giving the above display), the heating has come on, irrespective of the state of the Heat link.

Yes, that is correct.

You also say that you haven't removed any links within the boiler, before wiring in the Heat link - this suggests to me that the 24V RT link has been bridging the circuit so far.

I believe that the boiler was installed around 2016. This is the first time I have ever removed the front panel to get to the circuit board.

As mentioned, I inherited this boiler. I do not know if there was a room thermostat installed at any point.

I would remove all wires from the 230V RT terminals. (I.e. safely isolate the grey wire).
I would remove the 24V RT link.
And then, with the boiler turned on, (showing the standard display; with the heating control knob set to on), I would really hope that the heating didn't come on.

Please let me know if that makes sense.

- All wires were removed from 230V RT terminals

- 24V RT Link was removed

I can confirm that the central heating does not work

 

[RandomGrinch]

No, not at all.

The boiler switch is kept in the on position (as in the photo)

As with Vailliant boiler, I then have to use the control panel to turn on the CH, by selecting desired temperature and confirming the setting change.

That's a more complex procedure than I thought you would need - I was assuming that when you said the heating was working beforehand, all you were doing to get the heating to fire, was turning the knob to 'On'.

There may be a few too many variables going on here, for us to help with a remote diagnosis!

- All wires were removed from 230V RT terminals

- 24V RT Link was removed

I can confirm that the central heating does not work

Ok, again without any additional wires connected and ignoring Nest - if you add a link wire between L and 230V RT, does the heating come on?

 

[Mr Sparkle]

That's a more complex procedure than I thought you would need - I was assuming that when you said the heating was working beforehand, all you were doing to get the heating to fire, was turning the knob to 'On'.

On the Vailiant boiler to turn the central heating on you have to switch the knob to the 'on' position

Then do the following as shown in the video (i.e. from 10 secs-30 secs as shown in the video below).

However, once you have done the above once, the boiler will remember your chosen setting i.e. central heating 'on' and your desired temperature. So if you switch it off at the mains and switch the boiler back on, the central heating will automatically start running.

Ok, again without any additional wires connected and ignoring Nest - if you add a link wire between L and 230V RT, does the heating come on?

1. Do you want me to remove the incoming wire from the Heatlink that goes into the L, N, E and RT terminals on the boiler?

2. Then do you want me to Place a bit of cable to link the L and RT terminal?

3. The pic below is old, the red cable as shown in the pic is not actually wired in at the moment.