Is the new Nest Thermostat an appropriate option for Learning 2nd gen

[tmassingnest]

Is the base Nest Thermostat (not the 4th-gen Learning) an adequate replacement for the discontinued Learning 2nd-gen?  Also, is the existing harness compatible with either the new thermostat, or will it have to be replaced as well?

[EduardoN]

Hi @tmassingnest,

Thanks for contacting this community! I understand that you're wondering if the Nest Thermostat is the most adequate replacement for the discontinued Nest Learning Thermostat (2nd gen). At this moment, the basic Nest Thermostat is designed for certain types of more basic HVAC systems compared to the Nest Learning Thermostat (3rd and 4th gen), which is designed for many more HVAC systems including multi-stage systems, humidifiers, and dehumidifiers, since these have more wire terminals.

Compatibility with the new thermostat, and whether you'll need to replace your wiring, can vary depending on your specific wiring system. To give you a more specific answer, I'd like to ask you a few questions about your system.

• What type of furnace do you have? (gas, electric, oil, etc.)
• Do you have a multi-speed fan?
• Could you send me a photo of the wires that you have in your current thermostat?
• What is the make and model of your HVAC system?
• Do you have wire nuts in your wiring system?
• Is the voltage in your home high or low?

Visit our Help Center to learn more about Nest thermostat compatibility.

Please feel free to share any additional details you think might be relevant.

Best regards,
Eduardo

[tmassingnest]

Sorry for the delay.

• What type of furnace do you have? (gas, electric, oil, etc.) - Gas
• Do you have a multi-speed fan? - No
• Could you send me a photo of the wires that you have in your current thermostat? - Attached.
• What is the make and model of your HVAC system? - Trane Combined Heat/cool unit
• Do you have wire nuts in your wiring system? - No but Rc is dual connected Red/Blk
• Is the voltage in your home high or low? - Low
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[EduardoN]

Hi @tmassingnest,

Thanks for sharing that information about your system and your thermostat. Regarding the picture you included, I'd like to point out that the black wire should not be connected to both the RC and RH terminals. Only the red wire should be connected to the RC terminal.

By making these changes, your current wire configuration will be more correct and will also be compatible with the following Nest Thermostats:

• Nest Learning Thermostat (4th gen)
• Nest Learning Thermostat (3rd gen)
• Nest Thermostat
• Nest Thermostat E

Keep me posted.

Best regards,
Eduardo

[tmassingnest]

There is no source black wire.  The original system had the bridge.  It has been removed from all three Thermostat wiring connections. 

Back to the original question...Is the base Nest Thermostat (not the 4th-gen Learning) an adequate replacement for the discontinued Learning 2nd-gen?

Is it just the difference in "learning" vs manual schedules/temp?  Now that the wiring is correct, is the mounting frame compatible with the new thermostat, or does that need to be changed out?

[EduardoN]

Hi @tmassingnest,

Perfect! Now with the new information about your wiring configuration, it's much more practical to give you the necessary information to answer your questions. 

Regarding your question about whether the basic Nest Thermostat is a suitable replacement for your Nest Learning Thermostat (2nd gen), this will depend on your needs. Since we have different models with various features, I'd like you to review them so you can choose the best option for your wiring configuration. For reference, you can check out this article: Nest thermostat technical specifications.

Regarding the difference between learning vs. manual schedules/temp, with the Nest Learning Thermostat series, you have the "learning" option that adapts to your usage throughout the day, whether it's for heating or air conditioning temperatures. This doesn't prevent you from using manual schedules or temperatures.

There are differences between the models, and one of the most notable is the base where the wires are connected. Since these are different models, it is necessary to change the base. If you don't, the display will not fit correctly.

Keep me posted.

Best regards,
Eduardo