Boiler won’t activate with Nest

17 Oct 2023
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United Kingdom
Hi all,

Having some issues with Nest or boiler not sure what one is causing the issue. It’s a Biasi advanced 25c boiler with Nest 3rd gen thermostat.

Basically been working fine for the 4 years it’s been installed, went to test it out a few weeks ago and it wouldn’t fire up in manual mode but was working in scheduled.

Now this week it wont work at all, no issue with hot water, but boiler wont fire up for heating. I can hear the heatlink working when I turn the heating on and off but the boiler does nothing.

Pressure is setting at just over 1 bar.

It did work fine at the start of the year before it was serviced.

It’s not in summer mode as it’s showing the rad icon on the screen and no other errors.

Anything I’ve missed before I try and ring Biasi to see what’s going on?


Attached a photo of the heatlink wiring


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Let's try and rule out the Heatlink - connect the grey and black wires together, by sticking them both in either terminal 2, or 3.
If the heating comes on, the Heatlink is likely faulty.

Tried this and doesn’t do anything.

Replaced the whole system with a hive setup and it’s doing exactly the same thing, must be a boiler issue

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