Nest Support

Questions about Nest Learning Thermostat or Nest Protect: Smoke + CO alarm? We've got answers, videos, and plenty of resources to help you out.

Help with Nest Learning Thermostat wiring problems

If you're having trouble connecting the wires to your Nest Learning Thermostat or you're getting wiring errors, help is available. Below are articles that provide solutions to the most common wiring issues.

Getting Started

We have a troubleshooting tool that walks you through isolating and resolving the most common problems customers run into, including Nest Thermostat wiring errors. If that doesn't help, read through some of the articles below.


Installing the Nest Learning Thermostat (video)

If you've general questions about installing the Nest Learning Thermostat, watch this video first.

Watch now

My old thermostat had a short wire connecting Rh and Rc. How do I install this on a Nest Thermostat?

Unlike most thermostats, the Nest Learning Thermostat does not require a jumper wire between Rh and Rc. The Nest Thermostat knows if you have heating and cooling and just one R wire, the power source is shared between them.

Learn more

My old thermostat has two sets of labels for the connectors. Which ones do I use?

Some thermostats have different sets of connector labels, one for conventional systems and one for heat pump systems. To determine which labels are correct for your wires, you'll need to know the type of system that you have.

Learn more

Heating and cooling systems that are incompatible with Nest Thermostats

Nest Thermostats are not compatible with line voltage, millivolt, or low voltage systems with incompatible wires. Nest Thermostats are not compatible with some systems without a common wire installed.

Learn more

I have a dual fuel hybrid heating and cooling system. Is it compatible with the Nest Thermostat?

Dual fuel systems (also called hybrid or packaged systems) are a combination of a furnace (usually gas or oil) and a heat pump. The furnace provides an alternate heat source to the heat pump system. Dual fuel systems are supported by both generations of the Nest Learning Thermostat.

Learn more

Should my B wire go in the Nest Thermostat's O/B connector or in the common (C) connector?

Usually a wire labeled B goes in the Nest Thermostat's O/B connector. For some systems, the B wire is actually a common wire. The common wire (usually labeled C) brings power to the system. Common wires belong in the Nest Thermostat's C connector.

Learn more

The Nest Thermostat will not turn on after installation

The Nest Learning Thermostat will turn on automatically the first time it is connected to a power source. Normally, this power source is provided by the wires to your heating and cooling equipment. If the Nest Thermostat doesn’t turn on as expected, try the steps below to troubleshoot.

Learn more


Troubleshoot wiring errors

If you're Nest Learning Thermostat is getting a wiring error, try using out troubleshooting tool to get it resolved.

Start troubleshooting

The Nest Thermostat can’t detect wires that are installed

The Nest Thermostat detects wires by testing them in two ways: mechanically (is a wire inserted?) and electrically (is there an electrical signal on the wire?). If a required wire fails either of these tests, setup may not continue.

Learn more

When a Nest Thermostat needs a common "C" wire

While we find that in the vast majority of homes the Nest Thermostat can charge its built-in battery using the normal heating and cooling wires, about 1% of heating and cooling systems do require a common wire to provide a dedicated power line to the thermostat.

Learn more