NEST Thermostat and possible wiring problem

[tfitz1001]

Hi All;

First off, I am new here and a new homeowner, so bare with me:

1. Installed a new Nest Thermostat (well an electrician did) in beginning of summer
2. Ran A/C fine all summer.
3. Live in Northeast, so had boiler serviced last Friday by HVAC. He didn't touch the thermostat
4. Friday night my NEST shutdown due to low battery (first time ever happened), eight hours after HVAC was here.
5. Did some troubleshooting on Saturday, ended up frying the NEST in the process (while the NEST engineer was on the line--was the engineers at this point because they could not get to the bottom of the problem)
6. After we got it back up, he had me test the heat (which to date I don't recall anyone ever doing, only the A/C side)
7. NEST thermostat would not start heat due to an error code on the wiring. NEST support told me the error code was for overcurrent on W wire
8. Took off the heat and A/C, wired up "dumb" thermostat to A/C only for now until HVAC gets in to take a look.

Here's what I did before all of this happened.

1. Pulled off the NEST, checked the wires: Rh, G, Y - for A/C and then I checked Rc and W for Heat.
2. Voltage across Rh and Y and G and ALSO voltage across Rh and W. However, using the EMF Voltage pen, Rh is cold and W is hot.

What would you do next? If the answer is swap W and Rh, that's my answer too. BUT I do not know what the wiring "network" looks like from the thermostat down to the boiler, so I don't want to just blindly swap after reading some or the more complicated problems that can cause on a system that isn't just 2-wire direct.

Any advice would be appreciated. I'm getting a new NEST in the mail tomorrow and won't wire up the hear part until I know what's going on.

Thanks for any help in advance...as always when you start diving into a new field, you gain a sincere appreciation for all of the things that can (and do) go wrong.

Thanks
~T

[newoldtech]

Sorry per site rules no DIY.

Thread closed.