Can You Pit a Smart Thermostat on an Older Unit?

Nest thermostat compatibility

• Google Nest thermostats are designed to work with most 24 V systems, even older systems. They piece of work with all common fuel types including natural gas, oil, and electricity.
• During setup, the Google Domicile or Nest app will guide yous through steps to tell you if your arrangement is compatible with your Nest thermostat before you install it. The app volition besides give you a custom wiring guide for your thermostat.
• You lot can also check your system'southward compatibility earlier purchasing a Nest thermostat with our online Compatibility Checker.
• Some systems may require a common wire (C wire) or the Nest Power Connector. Go to g.co/nest/cwire for details.
• To check for compatibility, you just need to know the type of heating organisation. The specific brand or model doesn't matter. If you don't know what type of system you have, check your manufacturer'due south website or contact them.

Important: This article covers Nest thermostat compatibility in Canada and the The states only. To larn about Nest thermostat compatibility in Europe, go to Heating system compatibility with Nest thermostats.

Use the Compatibility Checker

The online Compatibility Checker has full instructions to check if your heating and cooling systems are compatible with Nest thermostats, but here is some boosted information to help you as yous use information technology:

How to turn your organization's ability off This protects you lot and avoids blowing a fuse in your equipment. There may be a switch on your system or near your organisation that looks like a regular low-cal switch. If your system doesn't have a switch, turn off power to it at the billow or fuse box.
How to test that system power is off Alter the temperature on your thermostat by at to the lowest degree 5 degrees. If it'southward winter, turn upward the temperature to turn on heating. If it's summertime and you have organization cooling, turn down the temperature. Expect at to the lowest degree 5 minutes to check if your system turns on (you lot'll need to wait considering many systems have a congenital-in filibuster). Tip: You lot can listen for your system to turn on, or put your hand most a vent to feel if there'southward warm or cool air that comes through.
How to remove your thermostat'south cover Some covers just pull off, while others need to be unscrewed. If you lot have an older thermostat, there may be a mid-plate that also needs to be removed to expose the wires. Acquire about thermostat mid-plates

Incompatible thermostat wires

If your thermostat'south wires are high voltage or stranded, then your organization isn't uniform. Just, information technology's possible that a trained professional tin can brand your system compatible.

Stranded wires Look closely at the end of one of the thermostat wires. You may need to pull 1 out of the connector to check. If there is more one big strand, the wiring isn't Nest-compatible. When you lot're done, reinsert it into the correct connector. Note: If your wires are stranded, you may be able to contact a local pro to cap, solder or supersede stranded wires with a solid core wire, which volition work with the Nest thermostat. The method may depend on your local electrical code requirements.
High voltage wires Loftier voltage systems typically have a thermostat that is labeled 120 V or 240 V, and has two thick wires with wire nuts. High voltage systems, such as electric baseboard heaters, aren't compatible with Nest thermostats. In some cases, it's possible that your system can exist fabricated Nest thermostat-uniform. Contact a local pro and accept them install a step downwards transformer to twenty - 30 5.
Take a picture of the wires Save a movie of your current thermostat'south wires in case you need help later on. Make sure that the connector labels are readable. Place thermostat wires
If your thermostat's connectors take two labels It tin can be hard to decide which set of labels to use in the compatibility checker. Refer to the following article for more than information: What to do if your thermostat's wire connectors have two labels
Ignore the wire colors Simply enter which connectors have a wire and ignore the color of the wires. This is considering not all systems are continued to the thermostat with the same wire colors. For case, don't enter R in the Compatibility Checker if you find a scarlet wire, or W if you observe a white wire. The label on the wire connector is what you should enter. So check R if there'due south a wire of any color in your thermostat'south R connector.
Don't enter jumper wires If your thermostat has a short "jumper" wire between 2 connectors, don't include that wire. Simply enter the labels for wires coming from within your wall that are attached to the thermostat. For instance, in the analogy on the correct, you would only enter Rh, Y1, G and C wires into the checker. You would not enter Rc in the checker, considering information technology is only connected past a jumper.

Learn more about compatibility

Systems that are Nest-compatible

In that location are some key differences between Nest thermostats and what systems will piece of work with each.

Annotation: Use this table for reference only.

System types	Nest Learning Thermostat	Nest Thermostat East	Nest Thermostat
Heat only, cool only, or heat pump systems			C wire or Nest Power Connector required
Natural Gas, Oil, or Electric fuel types
Unmarried stage heating and/or cooling			Heat only or cool merely C wire or Nest Power Connector required
Single stage heating with two stages of cooling
2 stages of heating with one phase of cooling
Single stage heat pump with or without AUX rut			C wire or Nest Power Connector required
Unmarried speed fan
Single stage heat pump with dissever unmarried stage furnace heating (Dual fuel)1			C wire or Nest Power Connector required
Unmarried phase heat pump with separate ii stage furnace heating (Dual fuel)i
Two stage oestrus pump with or without AUX oestrus
Ii phase heat pump with separate ii phase furnace heating (Dual fuel)1, two
Humidifier* or dehumidifierane, 2
Dual transformer systems1, two
Ii stages of cooling and two or three phase furnace  heatingtwo
Two or iii speed fani, ii
PTAC systems2

¹Your system requires advanced configuration and wiring. If you have one of these systems, contact a local pro.

Important: Professional installation is recommended for some systems since their wiring and setup can be complicated. These include:

• Dual fuel systems (estrus pump with furnace)
• Dual transformer systems (Systems that have more than i R wire)
• Whole-habitation humidifiers and dehumidifiers (compatible with Nest Learning Thermostat only)

² Nest thermostat can simply support one of these systems at a time.

About the C wire

The mutual (C) wire doesn't command heating or cooling. Instead, C wires assist deliver power from the organization to the thermostat in case the other wires tin't provide plenty power. Not all systems have a C wire installed, but Nest thermostats were engineered to employ every bit fiddling ability as possible for their display and internal circuitry. And so in many cases, they don't need a C wire.

Simply if you find that you need a C wire with a Nest thermostat, you tin install the Nest Power Connector. Or you can contact a local pro to install the power connector or run a C wire for you. Costs can vary depending on how difficult it is to route a new wire through your walls.

When the Nest thermostat needs a C wire

Compatibility with zoned systems

Nest thermostats are compatible with zoned systems, including zoned systems with dampers. All the same, there are some zoned systems that crave a C wire to piece of work with a Nest thermostat.

How the Nest thermostat works with zoned systems

Nigh the Nest thermostat's star connector

Nest thermostats also take a star connector * that offers you some flexibility to install specialized systems. The Nest Learning Thermostat'south * connector lets you lot install a humidifier, a dehumidifier, emergency heat, multiple fan speeds, or a 3rd stage of heating. The Nest Thermostat East's * or OB connector lets you lot install a rut pump, a second stage of heating, or a second stage of cooling. Learn more than about the star connector

Systems that are incompatible with Nest thermostats

While near 24 V heating and cooling systems are compatible with Nest thermostats, there are some systems that aren't compatible. You tin can speedily tell if y'all have one of these systems without having to utilise the Compatibility Checker or to wait at your thermostat's wiring.

If you have one of the organization types below, information technology won't work with a Nest thermostat.

Proprietary systems If y'all notice wires in your thermostat's connector that take non-standard labels (for instance 1,2,three, or A, B, C), your organisation is proprietary. If your organisation only has two wires, but y'all accept both heating and cooling, your system is probable proprietary. Proprietary systems aren't compatible with Google Nest thermostats. Nonetheless, some proprietary systems can be rewired past a pro installer to be compatible.
Millivolt heaters Millivolt systems are typically wall heaters or flooring heaters and utilize electricity or natural gas. These systems use much less electricity than low voltage systems and can't deliver the right amount of ability to Nest thermostats.
Loftier voltage systems Loftier voltage systems are unremarkably electric baseboard heating systems or other radiant systems powered past electricity. High voltage thermostats are often built into the wall and typically take 2 to four thick wires coming out of the thermostat. Wire nuts are oftentimes used to connect the thermostat to the system wires. High voltage thermostats are commonly labeled 110, 115, 120 or 240 VAC.Note: In some cases, information technology is possible to brand a loftier voltage arrangement Nest-compatible. Contact a local pro and have them install a step downward transformer to xx - 30 V. High voltage thermostats should only exist installed or uninstalled by a professional due to the loftier voltage that they deport.
Solid fuel systems Systems that use coal, wood fries, pellets, anthracite, or other biomass materials are typically incompatible with Nest thermostats.

Wired remote sensors

Remote sensor wires are typically used to give your thermostat exterior weather data. These wires can't be connected to Nest thermostats. Just Nest thermostats don't need wired sensors since they get weather condition information over Wi-Fi. Fifty-fifty if your system has sensor wires, it may still be Nest-compatible.

Some micro-controller based systems

Systems that use micro-controllers instead of relays are sometimes more sensitive to power sharing. If you have a micro-controller based system, your Nest thermostat may demand a C wire to be compatible with these systems.

Systems that tin can't evangelize enough power

Some systems can't deliver enough power (at least 20 volts) over the existing system wires, and then a Nest thermostat's battery may slowly drain and eventually crusade the thermostat to turn off. These systems are sometimes called high impedance systems. You may exist able to install a C wire to make your organisation uniform with a Nest thermostat. Contact a local pro.

Some arrangement hardware such as gas valves and zone or relay panels require a C wire to work with Nest thermostats. If you lot would like to observe out more data about installing a C wire, contact a local pro.

Gas valves

Some gas valves on systems vibrate or buzz when a Nest thermostat is installed. This can normally exist fixed by connecting a C wire.

Zone relay or control panels

Some systems have control panels or equipment interface modules that require a C wire to be compatible with Nest thermostats. Beneath is a listing of some known panels that require a C wire. This listing is non meant to be comprehensive, then your organisation may be incompatible even if it isn't listed here.

• Beutler ZTE2S
• Bryant 548F036
• Carrier HK42FZ011
• Honeywell AQ25110B
• Honeywell EMM-three
• Honeywell HZ221
• Honeywell HZ311
• Honeywell HZ322
• Honeywell HZ462
• Honeywell Trol A Temp MABS EZ
• Honeywell TZ-iv
• Lennox LZP-2
• Nordyne 624631-A
• Nordyne 903915A
• Villara ZTE2S
• Waterfurnace ATV045A 110CIT
• White-Rogers 36C03-300
• ZoneX DigiTract four
• Ztech ZTE2S

Incompatible arrangement wiring

Likewise many stages of cooling or heating

• Nest Learning Thermostats are only uniform with systems that have 1 or ii stages of cooling.
• The Nest Thermostat Eastward is only compatible with one stage of heating, i stage of cooling, and an additional phase of either heating or cooling.

International systems

• Some international systems, such equally Buderus boilers, take dry contacts or other incompatible wiring. These systems may require relay panels in order to be installed with standard American thermostat wiring.

Heat pumps with Fifty wires

• Fifty wires are typically used to show system status, like emergency heat being on. Nest thermostats tin work with systems that use Service Light (50) wires. While Fifty wires can't be connected to the Nest thermostat, information technology doesn't need them. The Nest thermostat and Nest app will evidence y'all arrangement status data without connecting Fifty wires.

Get pro installation for a dual fuel system

A dual fuel heating and cooling system (also chosen a hybrid or packaged system) is a combination of a rut pump for primary heating and cooling, and a furnace (commonly gas or oil) that provides a second and/or tertiary stage of heating.

The Nest thermostat is compatible with these systems and supports up to ii alternate rut sources.

You have a dual fuel system if you accept a furnace inside of your home, and a heat pump on the outside of your dwelling house. Oestrus pumps expect similar to air conditioners, so bank check the characterization on your outdoor unit to make sure it's a heat pump. If you lot're notwithstanding non sure which system you accept, contact a local pro.

If you have a dual fuel system, you will demand to have a trained professional prepare up your thermostat. It's important for a professional person to assess the requirements for your specific dual fuel configuration since choosing incorrect options for a dual fuel system can result in damage to your organization. Contact a local pro.

Thermostat wire labels

If y'all demand to know more than about what the labels on your thermostat wires mean, refer to the following article for more than information.

Thermostat wire labels

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Source: https://support.google.com/googlenest/answer/9246656?hl=en

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