Confused about my system and it's setup with nest

[Max1970]

I bought a house this winter and had assumed my HVAC had both heating and cooling but after installing nest I'm confused.

I initially had an older thermostat set with wires: W, R, G. The thermostat used R cable with a jumper on Rc and Rh; but the cable in the HVAC is connected to R. At the same time, there's a jumper between Y1 and Y2 in the unit.

I installed my nest thermostat rewiring G to C in both the HVAC and the thermostat (which I understand would limit my ability to self regulate fan, which I'm ok with).

However, Nest only shows me heating options now whereas the older panel used to show all options (I don't know if they worked, though, because I've never tried them).

Is it that the HVAC is only heating or have I limited it's use with my new wiring/thermostat setup?

Thank you!

[DeboraJ]

Hi @Max1970,

Thanks for reaching out to the community! I understand you have some questions regarding your system installation and Nest configuration. I'd be happy to assist you with that. And thank you for providing the details about your wired thermostat installation; that information is very helpful.

To give you the most accurate information, I'll need to ask a few questions before we continue: 

• What type of thermostat do you have?
• Do you know if you have a conventional or a heat pump system?
• Do you remember the brand of the old thermostat?
• If you have it, could you share a photo of the old thermostat's wiring?
• Could you share a photo of your current thermostat's wiring?

I'll be more than happy to assist you once you have that information.

Best regards,

Debora

[Max1970]

Hi Deborah, 

My new thermostat is the regular nest (not the learning or E).

I believe it's a conventional furnace (Lennox brand).

The old thermostat brand was White Rodger. 

I cannot attach pictures to this forum for some reason, but the wiring is as I described:

The furnace had 3 wires. W, R, G. And a jumper on Y1 Y2. These 3 wires were connected on the old thermostat to the respective W, G, and Rh with a jumper to Rc.

For my nest setup, I connected W and R but repurposed G as a C cable connecting it to C on both ends.

Hope this answers all questions!

[DeboraJ]

Hi @Max1970

Thanks for the follow-up and the detailed information! Happy to help further.

From what you've shared, your HVAC system supports both heating and cooling, but the thermostat is only providing heating. This is likely due to the current wiring setup, where the G wire has been used as a C wire, connected to C at both ends (HVAC and thermostat).

To get both heating and cooling, you'll need to remove the jumper from the Y1 to Y2 terminal and place it on the Y terminal only. You don't need a jumper with the Nest thermostat. Also, keep in mind that a dedicated C wire is essential for powering your thermostat and isn't for heating or cooling. For cooling to work, you'll also need a G wire, which requires running a new wire from your HVAC system to the thermostat. This applies to both the C and G wire setups.

After you've adjusted the wiring, please factory reset your thermostat and set it up again in the Google Home app, choosing the conventional system.

Let me know if you have any questions.

Best regards,

Debora

[Max1970]

Thank you Debora!

 I have a question: with this configuration, would I be able to avoid the re wiring if I have the learning thermostat?

It would be easier for me to change the thermostat than re wiring the whole thing.

Thanks!

[DeboraJ]

Hi @Max1970

That's a good question! Just to clarify the rewiring process, you'll need to work directly with your thermostat wires. Your Google Nest Learning Thermostat can control both heating and cooling systems, but connecting your Y1 wire is necessary to enable cooling. If you skip this step, you can still use your thermostat for heating only. However, if you're not comfortable with this process and decide to change your system in the future, we recommend contacting us by phone or chat for more assistance with that process.

Let me know if this information is helpful! I'm happy to assist you further.

Best regards.

Debora