Combo-Boiler turning on, thermostat set to off.

[ecrespo175]

I have a Navien NCB-240E combi boiler that was installed back in May by my contractor, 2 Honeywell Smart Thermostats were installed as well. Two weeks ago I noticed that the unit starting sending heat to zone 1(Main floor). My contractor sent a tech in yesterday and said it was the thermostat calling for heat, even though it was set to off. Luckily my electric company was running a promo and I had purchased 2 google nest thermostats for $1 each. So I handed the tech the google nest to swap it out, also told him to swap out the one in my main bedroom(zone 2). After swapping both he also changed the wiring from my first floor, said it also might be the cables touching each other. 15 minutes after he left, I noticed the main floor google nest had a "no power error" seems the common wire was not installed. I went upstairs and realized it was very hot, sure enough the baseboard was throwing heat. The google nest upstairs was set to off as well. Called back my contractor, tech came in today again. He called Navien and they are continue to blame the thermostats. He showed me that once one of the google nests faceplates are mounted to the wall, the combi unit starts dishing out heat. He then thinks that it's the thermostats again. I'm at a lost here, I can't believe 4 thermostats are somehow calling for heat even though they are in the "off" position. Has anyone ran into this issue, if so what was the cause?

 

[Gasmk1]

I would say either incorrectly wired also need to check dip switches are all correct on the pcb, never seen one but that was quick look at the downloadable instructions

 

[John Calano]

Newly installed Navien NCB-240_110H combo boiler turns on when the thermostat is set to off. Only one newly installed thermostat for the whole house. Same issue as ecrespo175. Any resolutions?

 

[John Calano]

Problem solved. It was the thermostat wiring. Must have shorted somewhere along the path. Thermostat was good.

 

[Jamone B]

Problem solved. It was the thermostat wiring. Must have shorted somewhere along the path. Thermostat was good.

Nest setup hi John can you send me a pic of your setup please don’t know y mines not working