Nest Learning Thermostat setup - blows hot air instead of cold air

[mrbijus76]

I have finished setting up the new Nest Learning Thermostat. However A/C is blowing hot air instead of cold air when the setting is in cool or testing for cooling.

Old thermostat wiring was like this (cold not upload image)

red - RC, yellow-Y, blue-C, orange- W, green-G, white-W2 (There is a jumper between R and RC)

By Following the instructions from Nest App, the wires were connected to the Nest Learning thermostat as below.

red-RC, yellow-Y1, blue-C, orange-W2, green-G, white-W1

All wires are shown as connected in the Equipment Detected  screen, however always getting hot air instead of cold air in the cooling setting or testing cool. Noted that Nest App ->Equipment shows only Heating wires not cold wires. Tried resetting/reinstalling etc..  Works fine when connecting the old thermostat back.

Can anyone please provide input into what could be the problem here.  A/C is conventional , no heat pump

[luciaaa]

Hi, @mrbijus76, 

Thank you so much for reaching out to the community. I’m truly sorry your system is blowing hot air instead of cooling air. I'm happy to assist you and find a solution.

Thank you for the details provided. Based on that information, it seems your system is compatible with our Nest thermostats.

To assist you further, please confirm the following:

• Have you removed the jumper? If not, remove it and only connect the red wire.
• Do you have a heat pump system or a conventional system?

Follow these steps: 

• Turn off the breakers.
• Connect the wires as follows:
  • Red wire to RC
  • Yellow wire to Y1
  • Blue wire to C
  • Orange wire to W1
  • White wire to W2
• Ensure all thermostat wires are securely inserted into the correct terminals and the buttons next to the terminals are pushed down.
• Turn on the breakers.
• Reattach the thermostat display.
• Perform a factory reset on your thermostat and set it up.

Please let me know how it goes.

Best regards,

Ana

[mrbijus76]

@luciaaa  Thank you for the response. I have followed your instructions, but unfortunately that didn't make any difference. Yes, I had removed the jumpers and my system is conventional Carrier HVAC no heat pump. The only difference in your suggestion with my previous setup was Interchanging Orange and White wires. I have ensured that all wires are properly connected,  and did a factory reset. Still, hot air is blown instead of cold air in cooling mode.. 

I don't have permission to upload images here, if you can share your email, I can share the pictures of my wiring, device and nest app. One thing I noticed is that , the Nest thermostat shows Equipment sensed on W1-Y1-G-W2/Aux-RC, however the in Nest App->Equipment->System Details shows  Heating Source1->Electric, Heating Source2->Electric, Heat Type1->Forced Air, Heat Type2->Forced air, no cooling type shown there... not sure if that's normal or not. Ensured multiple times that the wires are secured (not able to pull it without pushing down the buttons on the terminal).

Please let me know if you can provide any other suggestions. I thought setting this up is simple, and it was.. but unfortunately it is not sending the correct signal to the HVAC it seems.

Thank you for your help

[luciaaa]

Hi, @mrbijus76,

Thank you for your response and for completing the troubleshooting steps. I apologize that your system is still heating instead of cooling. I’m happy to help.

To assist you further, please provide the following information:

• Are there any error messages on the thermostat?
• When was the last time your HVAC system was serviced?

Since the previous steps didn’t work, please try this:

1. Turn off the breakers for your HVAC system.
2. Swap the Y1 and W1 wires (yellow and orange).
3. Turn on the breakers.
4. Reattach the thermostat and set the system to heating mode. Expect the AC to turn on.

Please let me know how it goes.

Best regards, 

Ana

[mrbijus76]

There are no errors, HVAC system was serviced last month and everything works good on connecting back the old thermostat.

I've tried your suggestion to swap wires and here are the results . With outside temperature 77 and thermostat temperature set to 80, on heat mode the HVAC system is blowing hot air , when temperature is set to below 77 , the system just shuts off. On the  same setup in cold mode if the temperature is set below 77 only the fan is working.

Thanks,

Biju 

[aperezdeleon · Accepted solution]

Hi mrbijus76,

Thanks for replying.

Due to the system's behavior after you swapped the wires, I think it would be a good idea to double-check the wiring labels on your original thermostat.

Some thermostats have two labels: one for conventional systems and another for heat pumps. As a general question, do you have two pieces of equipment in your home? If so, you likely have a conventional system, typically a furnace and an AC.

However, if you only have one piece of equipment that handles both heating and cooling, you probably have a heat pump. In that case, the orange wire originally on W1 should go in O/B on the Nest thermostat to control heating and cooling. If this wire isn't connected, it could explain why your system is only heating even though the fans are working correctly.

Do you happen to know the make and model of your HVAC system? Before trying a heat pump configuration, it would be helpful to know which type of equipment you have. If it’s not a heat pump, as you mentioned, we can find a wiring diagram to determine what your wires control.

Let me know how it goes.

Regards,
Angel.

[mrbijus76]

Hi Angel, Thank you very much for those details. My understanding about conventional vs heat pump system was completely wrong, Yes, you are right, my system is heat pump, I have followed heat pump configuration prompts to successfully install the thermostat. Thank you for your help and thanks to @luciaaa  for providing initial guidelines which helped to identify the issues.