Boiler not starting

[Todd12]

Hi,

My boiler wont start when I turn the Nest thermostat on to heat the room. 

I set the thermostat to 23C to heat the room (its cold,18C) but the boiler won't start unless I press the heatlink button once. 

The boiler is working fine - it was checked last week.  The heatlink is clicking on but the boiler isn't starting.  The heatlink is green, and I have reset it a couple if times - held the button down for 20 seconds and it resets. 

I have a vailiant ecotec 820 boiler, and the Nest thermostat is a gen 3, and the heatlink is on 240v power.  I have never had an issue with it in 4.5 years until now. 

What is happening here?  I suspect there is an issue with the heatlink.  Does this happen regularly, and do they occassionally need replacing? If so, who do I call for help on this type of issue?

Any help would be appreciated.  Thanks.

[Frustratedddd]

When you turn the display dial to call for heat do you here a click then at the Heat Link?

Why do you think there is a problem with the Heat Link, if the boiler is firing up when pressing the Heat Link button?

[Todd12]

Hi,

Thanks for replying.  As I mentioned, the heatlink is clicking on but the boiler isn't starting. 

The boiler does start when the heatlink button is pressed, however, I shouldn't need to press it once the thermostat dial us turned on for heat. 

Logic says to me, there is an issue with the heatlink telling the boiler to start when the thermostat demands it.

Ta.

[Frustratedddd]

Yes your logic you would think is correct, but the boiler fires when pressed with the button, meaning the relays are working.

You also state that the Heat Link is clicking when calling!

However, do you have any motorised valves in the system? More to the point have you checked they are working?

[Todd12]

As I said, the bkiler is workinv fine, it was checked last week. 

[Todd12]

Sorry  hit send before I finished.  As I said, the boiler is working fine, it was checked last week.  Maybe a gas valve issue then you think? 

[Frustratedddd]

Like I said, have you checked the motorised valves, NOT a gas diverter valve?

Boiler service does not check motorised valves, hence me asking!

The only other way to prove is to check terminal 3 [and 6 if connected for a system boiler] to see if they are switching. Should terminal 3 switch, then it aint your Heat Link!

[Todd12]

Surely I need a qualified person to be checking this?

[Frustratedddd]

I’m not saying you don’t, but don’t assume it’s the Heat Link.

My comments about have you checked, doesn’t mean you personally , it’s a figure of speech. 

Arrange for an electrician to have a look, they can then prove the Heat Link is switching or not.  You have to start somewhere, and you say it’s NOT the boiler as it’s working fine!