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.

How can I tell if I have a heat pump or conventional system?

Heat pumps are controlled and connected differently than conventional heating and cooling systems. Here are some tips to help you determine which type of system you have.

The first step is to remove the cover from your current thermostat. You will see a series of labeled connectors. Take note of the connectors with wires.

If you have an orange wire connected to O (or O/B), or a brown wire connected to B (or O/B), you probably have a heat pump.

Many thermostats have 2 sets of labels for each connector: 1 for conventional systems and 1 for heat pumps. In that situation, it can sometimes be difficult to tell what you have. See the article below for more details.

My old thermostat has two labels for each connector

Important Note: Some thermostats for conventional systems use a connector labeled with a B for the common wire. If you have a wire connected to B and no connector labeled C, you may have a conventional system with a common wire. If your current thermostat’s connector labels are confusing, check your heating and cooling equipment. If you have a condenser unit that is a heat pump, it will usually say “Heat Pump” or “Package Unit.” For more information on B wires, see the article below.

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

Once you’ve determined if the system is a heat pump or a conventional heating and cooling system, you’ll know which labels to use while installing your Nest Thermostat. If you’re still not sure, we recommend that you use our Check Compatibility tool or contact a Nest Pro installer for help.