Wiring or system issue on install NLT4.0 RH or RC no power E448 error

[hitin22]

carrier programmable thermostat 

Hi! 
I’m having issues installing the thermostat. 
Getting no power from Red RH wire.

Currently have:

Yellow Y1

Green G

White W1

Blue C

Red RH

Tried two zones and having same issue

1. Could you please send a picture of the previous wiring configuration?  - attached
2. When you install the new Nest Thermostat, it shows you an error message. or the thermostat doesn’t turn on. - setup is not able to detect power from Red wire
3.  Also, please confirm the model of Thermostat you want to install and what type of HVAC you have. -- NLT 4.0. HVAC type (electric furnace)

[hitin22]

carrier programmable thermostat 

[Jeremyg]

Hi @hitin22,

Thank you for posting in the community. I am sorry that you are having issues with the wiring or system thermostat and it has an E448 error code, but no need to worry; help is here.

I need to know a few things about your thermostat in order to provide you with a better resolution.

• When did the issue first occur?
• When was the thermostat installed?
• Did you install the thermostat yourself?
• What is the voltage on the red wire?
• During the setup, did you select ‘Google Nest or partner device’ instead of ‘Matter-enabled device?
• What network do you currently use, 2.4 GHz or 5 GHz?

I'll be waiting for your response; any additional details you can provide will be helpful.

Best regards,
Jeremy.

[hitin22]

Hi Jeremy,

Thank-you for your response.

• When did the issue first occur? -- it occurred the first time I am trying to setup the new NLT4.0 thermostat.
• When was the thermostat installed? -- last friday as I was trying to setu it up
• Did you install the thermostat yourself? -- yes
•  What is the voltage on Red Wire? -- I do not know how to check or where to check this
• During the setup, did you select Google Nest or partner device instead of Matter-enabled device? -- I selected Google Nest. I dont remember getting any other option.
• What network do you currently use, 2.4 GHz or 5 GHz?  -- 5 Ghz

[Jeremyg]

Hi @hitin22!

Thanks for the update and letting us know that information that is going to help me to better assist you.

Here are some general tips to exhaust all the possible issues:

• Detach the display from the base.
• Plug it into a USB port.
• Plug it into a power outlet or computer.
• Leave the display attached for 2 hours.

Let me know how it goes and keep me posted.

Best regards,
Jeremy.

[johnforestolson]

I'm having the same problem with my new Google Nest Learning Thermostat. When I plug either the Rc or the Rh wire in, a light comes on behind the spirit level in the connector plate: so clearly there *is* power on both, though I couldn't tell you what the voltage is. Nonetheless, installation halts with E448 complaining that there's no power on Rc or Rh. 

I currently have the display plugged into a USB charger, per the last comment on this thread.

[johnforestolson]

Tried again after the thermostat had been plugged in for a couple hours. Now it gets to the failure screen faster, but it still fails with E448.

[johnforestolson]

I bought a multimeter and confirmed that I have 24V AC between Rh and G or W and between Rc and G or W. Both Rh and Rc have 5V AC against Y1. There is no voltage difference between Rh and Rc. So it sure looks like I have power, even though the thermostat keeps insisting there is none.

[Jeremyg]

Hi @johnforestolson!

Thank you for posting in the community. I am sorry to hear that you're having the same issue. In this case, can you please share with me the following information about your Nest Thermostat that is going to help me to get a conclusion?

• Go to your Nest Learning Thermostat 4th gen.
• Go to the settings. 
• Tap on equipment
• Then tap on Wiring Info.

Let me know how it goes and keep me posted.

Best regards,
Jeremy.

[johnforestolson]

I finally called the help line, and got good advice. Turns out the problem was that both Rh and Rc were hot; the thermostat only wants power on one of them. I unplugged Rc, and everything worked. The configuration tool ought to tell you this.

[Jeremyg]

Hi @johnforestolson!

Thanks for posting here in the community! I'm glad to hear that the issue has been resolved, and I also appreciate all the efforts you've been making to resolve this inconvenience. If you encounter any other difficulties, please post again in the community.

Best regards,

Jeremy.