Nest and Baxi boiler - I am learning, please help me?

[Kool KG]

Hi All,
Glad to join the forum, so many experts here, well done all.

Month ago I have replaced my boiler with Baxi 630 Combi (believe this is a fully Opentherm compatible boiler?), and connected with Nest 3rd generation thermostat. Installer was great, but not good with the new technology, but found some guides on the internet to show him how to wire the thermostat. All are working okay, but just discovered couple of issues, (Nest and Baxi technical help are useless, they keep referring to each other for help) hoping someone can help me please?

1. Even though nothing changed in the house, Nest thermostat lost connection to Heatlink three times this week. Managed to get them connected. Thermostat is in the same room as boiler now, but this is not ideal? I like to move the thermostat back to landing area. What causes the issues with lost connection between Nest thermostat and Nest heatlink?

2. I have connected Nest heat link as follow. Heatlink N & L to Boiler N & L (Block G) and removed the link between 1 & 2. Nest Heatlink OT1 & OT2 to Boiler block H connections 1 & 2. No other wiring between Heatlink and the Boiler. When thermostat is connected to Heatlink, I can control functions as expected. But last night, try to test the Nest Manual override function. Instruction was to click once middle large button on the Heatlink to start the boiler on manual state. Boiler fired up, but no call for heating or heating start to come on!

a. Can you please confirm, above wire connections are correct so far?
b. Do I need to connect any other terminals to fire up the boiler for heating with Nest manual override mode?

I have attached the couple of screen shot for the connections. I will be so grateful, if any of you can help me please?

Thanks in advance.

 

[stem]

The connections for Nest to an OpenTherm combi boiler are as you describe and shown in the manual. N, L, OT1 & OT2. That's it. (Unless you have chosen to connect the thermostat to T1 & T2 for its 12v power supply.)

I'm not sure about the link between G1 & G2 most boiler instructions say 'remove it when fitting external controls' but for some boilers that means only when fitting external controls to the terminals where the link is physically fitted, but not when using OpenTherm. However, if it has been working OK without it fitted, then that's how it should be.

Someone who is familiar with your particular boiler would be able to advise definitively, but it's fairly easy to work out:

1) If the link should be present for OpenTherm, then the heating would not come on at all if it was missing.

2) If the link should not be present for OpenTherm then the heating would be permanently 'on' if it was fitted.

It sounds like you are probably loosing communication between the Heat Link and the Thermostat. If the Heat Link is mounted too close to the boiler (it should be a minimum of 30cm away from it) it can shield it from the Thermostat's signal. Other metal objects between the two can also block the signal. I went to an installation with a similar problem that had originally been commissioned OK, but afterwards the users reported communication problems. I discovered that they had afterwards positioned a microwave on the counter directly in front of the Heat Link.

The distance between the two is less likely to be a problem, but it should be less than 30 metres, and as already said devoid of large metal objects. For example, some wallboard's can have a foil lining which may not be visible. If the Thermostat and Heat Link maintain communication when they are closer together, it would indicate that something is blocking their comms when the Thermostat is on the landing.

Instruction was to click once middle large button on the Heatlink to start the boiler on manual state. Boiler fired up, but no call for heating or heating start to come on!

I'm not quite sure what you mean by that, are you saying that when you pressed the button the light with '3 wavy lines in a circle' lit up, the boiler fired up, but the heating didn't come on?

 

[Kool KG]

Hi Stem, you are a star, thanks for the speedy reply.

1. My Nest thermostat is not hard wired, so I am assuming don't need the T1 and T2?

2. Installer removed the link between G1 and G2, Nest is working fine. So assuming this is correct?

3. When I connected the Heatlink OT1 and OT2 to boiler Opentherm connector H1 and H2, I understand I can connected to any terminal ie: OT1 to H1 or H2, OT2 H1 or H2. Is that correct?

4. Nothing changed in the house, wireless Nest thermostat and boiler was working fine since the installation for 6 weeks. Losing the connection only started this week and failed three times so far!

5.

I'm not quite sure what you mean by that, are you saying that when you pressed the button the light with '3 wavy lines in a circle' lit up, the boiler fired up, but the heating didn't come on?

Thats correct, need to find out what is the problem and how can I start the boiler heating without Nest thermostat?

Thanks again Stem, look forward to hearing from you.

 

[Crofton Gas]

Are you sure the nest opentherm is not holding boiler off due to inside/outside temps?

 

[Kool KG]

Hi Crofton, Many thanks, good question.
I don't think so, because I tested this function on Thursday night 8.30pm.

Currently Nest Heatlink is connected to Boiler L & N (G4 & G5 on the diagram above) and Heatlink OT1 and OT2 connected to Boiler H1 & H2. No other wire connections between Nest Heatlink or Boiler. According to boiler manual, when I connected as Opentherm, boiler will lose the control of temperature control. So when I click Nest Heatlink middle large button to set for manual mode, I can see wavy and water green light comes on, boiler start to run, but no heat on the radiators or call for heat? Do I need any extra wires connected?

When Nest thermostat is connected to Heatlink wireless, all working good. But I have lost wireless connection three times now and kids came home and house is very cold. So override function to turn the heating is so important to me and I don't want to be stuck again.

Can you please help?

 

[ianmcd]

is your nest thermostat fitted on the wall or is it on a stand ?

 

[Kool KG]

is your nest thermostat fitted on the wall or is it on a stand ?

Thanks Ian, it is on a stand

 

[ianmcd]

try placing the stand next to the receiver, TVs and electrical appliances can affect the transmission between the two

 

[Kool KG]

try placing the stand next to the receiver, TVs and electrical appliances can affect the transmission between the two

Thanks Ian, thats' what I did and seem to be okay and not lost connection for 24 hours. But this is not an ideal location for my thermostat and would like to move back to landing, lets see.

Do you have any idea for my Nest Heatlink manual override issue (listed above) please?

 

[ianmcd]

over ride function should work regardless of the location of the thermostat, the over ride button is just a switch that tells the boiler to come on for heating, how is the nest powered ? is it a USB cable going into a plug ?

 

[Kool KG]

over ride function should work regardless of the location of the thermostat, the over ride button is just a switch that tells the boiler to come on for heating, how is the nest powered ? is it a USB cable going into a plug ?

Thanks again. Thermostat is connected via USB plug, Heatlink is connected to L&N in Boiler. When I click the Heatlink button for over ride, Boiler turns on but no heating. When heating is on, normally an icon (like radiator symbol) on the boiler flashes. But with manual over ride this icon is steady on. So that's why I know heating is not on or there is no call for heating!

 

[ianmcd]

I think you may have a set up issue with the open therm settings, call nest, they can see your settings from their end and can adjust them

 

[Crofton Gas]

Think the override button only switches relay on the 240v side

 

[Kool KG]

I think you may have a set up issue with the open therm settings, call nest, they can see your settings from their end and can adjust them

Thanks Ian, correct, it is an Opentherm connection (Live, Neutral, OT1 and OT2). My Boiler is Baxi 630 Combi, which is Opentherm compatible. I did call Nest, but they want me to get a Nest Pro out, huge £100 bill?

 

[ianmcd]

they can test it from their side , they can look at your install and test it without calling anyone out