Heating not turning on boiler

[samdl2]

We have recently installed a Nest learning thermostat replacing a very old Honeywell program unit.  

All seemed to be fine and it works to turn on our hot water however when we test the heating it says its turning on but the boiler doesn't fire up and the radiators don't get warm.  

We have a gas system boiler and  a hot water tank with a three way valve that switches between hot water, heating and both.  The nest was installed with the Y plan wiring and seems to be providing a signal (the heat link is green status light plus if you test voltage when turning heating on it comes on)

We are baffled and plumber thinks it may be the control valve that is at fault not the nest but seems strange that it was all working fine before we installed the Nest.  

Any help would be appreciated as plumber can't get out to us for at least a week (obviously don't need heating yet)

[DragosC]

Hi there @samdl2.

Thanks for letting us know. From what you've explained to us, it seems the thermostat gives the signal to the Heat Link and the Heat Link sends the signal to the boiler. Which means the valve could become stuck. If you've tested the Heat Link with a multi-meter, there should be no doubt that it;s doing its job. 

[AlexD]

Hi, I wanted to check in. Do you still need assistance with your device? if so, make sure to let me know.

[samdl2]

We’re awaiting our plumber coming to have a look next week as hoping it’s the three way valve that is the problem not the nest. Fingers crossed 

[george_t]

Hi @samdl2. Thanks for the details. Let me know the result after the installer checks your system.

[samdl2]

just posted an update, valve replaced but still no heating, any ideas?

[DragosC]

Thanks for letting us know. That's weird. Could you tell us please if the installer performed a continuity test with the multimeter on the Heat Link? 

[samdl2]

Well as my husband installed it when the heating was not working but hot water was he put a volt meter on the wires into the heat link and when the heating was turned on they went live (not sure if that's correct working) so that's why it made sense that it was a more mechanical problem.  

What I'm wondering now is that we had an old thermostat hard wired in the hall and it has been removed but the wiring is still there I think but not connected to the Nest, could this be the problem?

[DragosC]

Almost, but no. The voltage and continuity are 2 different things. We need to see if the Heat Link has continuity and all the connectors and relays inside are working properly. I've sent you the instructions for the continuity test over email. Please check on them whenever you have time and let me know how it went. 

[AlexD]

Hi, I wanted to check in. Did you get the email from my colleague?

[samdl2]

Hi, yes I thanks. We got an electrician to come and have a look. Turns out where the old thermostat had wires going to it we had been left with an open system. He removed the wires that weren’t needed and also changed a connection in another wiring box so it’s all fixed now 

thanks for everyone’s help 

[AlexD]

That is great to hear. Thanks for all the troubleshooting done. I'll go ahead and close this thread but if anything comes up, don't hesitate to open a new one. 

[DragosC]

Hi there. I'm just following up on our last message. Do you still need our help? Keep us posted. 
 

[samdl2]

Hi, plumber has been and replaced the three way control valve however our heating is still not turning on.  

He is not confident to look at the wiring as he doesn't do electrical side of installs.  We're now stuck waiting for him to try and find us an electrician to look at wiring.  

As we installed this ourselves any help would be appreciated.  

The only thought is maybe something to do with the wiring that went to the old thermostat as this has been disconnected but we assumed the nest has its own heat sensor so doesn't need those wires just power