Replaced boiler, now gen 2 Nest Learning thermostat isn't working as expected

[regexaurus]

We have a gen 2 Nest Learning thermostat that we've been using with no problems for years. Our boiler was replaced last week with a high-efficiency combi boiler, NTI model FTVN199C. When the installer connected the thermostat wires to the Nest base W1 and H1 terminals, as it had been for our old boiler, the system immediately called for heat, even without the thermostat on the base. The system is working fine with a Honeywell TH4210U2002 thermostat connected for now, wired as the Nest base had been, though the terminal labels are slightly different (W and R). It seems oddly coincidental to me that the Nest (base?) would fail at the same time the boiler is replaced. I took the Nest base plastic chassis apart (4 screws). Capacitors appear good and I see no problems with the board (browning) and smell nothing burnt. I think the W1 terminal push button feels slightly "softer" (gives way easier) than the other push buttons. Can you offer suggestions for further troubleshooting? If there is a problem with the W1 terminal, could I use W2/AUX instead? If so, would I still use RH or would I need to switch to RC? I'm assuming if this would work, I might need to reconfigure the thermostat to "understand" my system...?

Thanks in advance!

[regexaurus]

I just saw this reddit post: Nest Learning Thermostat calling for constant heat even when heat turned off. The trouble seems similar, except the poster states that his boiler goes into standby mode when his Nest Learning thermostat is disconnected from its base. I'm wondering whether a C wire is a possible solution in my case, as commenters suggest on that reddit post...?

[zoeuvre]

Hi regexaurus, 

Thanks for posting here in Community, and I'm sorry for the late reply. Let's sort this out. 

Please send us a photo of your thermostat wires connected to your boiler's control panel and how they are connected to the Nest Thermostat base. I'll look forward to your response.

Best,

Zoe

[regexaurus]

Hi Zoe,

After searching the webs, I purchased a 24V transformer/adapter, connected it to my Nest's C and Rc terminals, and reconnected the boiler system thermostat wires to the Nest (W1 and Rh). Unfortunately, this didn't resolve the problem, and the system immediately called for heat.

I called NTI support and was told I also need an isolation relay wired in. I've done some research on this and I believe I have ordered the parts I need. The final part I need is expected to arrive today. I plan to follow up here with my progress.

[zoeuvre]

Hi there,

How's it going with your Nest Thermostat? In case you have an update, let us know and we'll be happy to help.

Best,

Zoe

[zoeuvre]

Hi regexaurus, 

We haven’t heard from you so, I'll go ahead and lock this thread within 24 hours. If you run into any more issues in the future, please feel free to create a new thread.

Regards, 

Zoe