I just got back from a 3 day trip last night, and found my house at 50°F. I have a nest thermostat, and it will not turn on the boiler, only by turning up the temp on the water heater will it kick on. I only have 2 zones, one for baseboard heating (whole house) and the other for the water heater. The nest is functional and not the issue - I swapped out for a brand new thermostat already to verify if the thermostat was bad or something else could be the case.

Turning the switch on (the light switch looking thing next to the boiler) has the control board pressure switch light blink red only once, and nothing else happens. All the lights come on and looks ok when the water heater gets the boiler fired up. I have a feeling it may be the relay for the thermostat - is there any way I can easily test this, and if it is dead, is there a way I can manually start it and heat my house up to temp at least for a little while?

 

You must have electric zone valves then, is that correct?

What make/model is the boiler?

 

Also post the aqua stat model #.
Geo