Best Smart Thermostat without C Wire

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When most of us plan to have a thermostat for a smart home, we start looking online for the best thermostat. And some of us who are more informative may want a smart thermostat with multiple zones feature as they are better equipped to control different temperatures in different rooms.

But then there is another concept related to home wiring that opens up a new dimension to your new purchase. The role of the c wire is important in thermostats.

You may be having an old or new HVAC system but if you don’t have a c wire in your home, make sure you buy a smart thermostat without a c wire.

What is C Wire?

nest smart thermostat opened with c wire
Nest Smart Thermostat C Wire

A C-Wire or common wire is a cable that acts as a continuous source of power for a smart thermostat.

The most important question is what do you do if your wiring does not have a c wire?

Are there any smart thermostats that work without c wire?

There are a few good smart thermostats available that don’t require c wire. But our honest recommendation is to have a c wire installed. It is worth the effort. We have also listed some alternatives to c wire installation at the end of the article.

Here are our top three recommendations for thermostats without c wire or one that includes an adapter.

Recommended Smart Thermostats with C Wire

1) EcoBee SmartThermostat with Voice Control

Ecobee SmartThermostat with voice control is the most advanced thermostat from Ecobee. This is an upgrade to the already popular ecobee4.

Like all ecobee thermostats, it comes with a power extender kit which acts as a replacement for c wire.

This power adapter is connected to the furnace control board using existing wires and acts as an intermediary for c wire extension. The thermostat wires, RGWY are put into RC, C, PEK, and W1 terminal in ecobee respectively.

The power extender kit provides a continuous supply of power to the thermostat.

Here are some standout features apart from the c wire alternative feature.

  • Powered quad-core processor and dual-band Wi-Fi.
  • 23% energy saving leading to lower power cost. 
  • Ability to learn and adapts to your schedule.
  • It comes bundled with one SmartSensor for multiroom temperature adjustment.
  • Inbuilt Alexa and BlueTooth support for streaming your favorite Spotify lists.
  • It supports integration with Alexa, Google Assistant, Apple Home Kit, Samsung SmartThings, and IFTTT.

2) Nest Learning Thermostat without C Wire

Nest learning thermostat, a google product is another strong contender if you are looking for a smart thermostat without c wire.

The Nest is equipped with inbuilt batteries. It draws power from heating and cooling wires to recharge its batteries. But even google clarifies that the optimal performance of the thermostat can be achieved through c wire.

There can be rare instances of batteries that may not be able to deliver consistent power to the thermostat. In such cases, there may be some sound of the system turning on and off. Or the Nest Thermostat screen may show a delayed start time notification.

Additionally, do make a note that some control panels, micro-controllers, and gas valves do require c wire. So to make them compatible with Nest will require a C wire.

Here are some notable features that contributed to Nest to this list.

  • Like EcoBee, it can learn and adjust the schedule and routines to save energy.
  •  Home Away Feature: The motion sensor feature detects if you are at home and adjusts the unit accordingly.
  • It works in conjugation with other Nest products like Nest Camera or smoke detector as they can inform the thermostat that you are at home.
  • Farsight Feature: The Nest screen light whenever someone enters the room and shows the current status of temperature, time, and weather.
  • Humidity Sensor: It can also detect the current humidity level. If the house is equipped with a dehumidifier, it will make the desired changes.
  • Multizone Support: With the help of the room sensor, Nest can adjust each room or zone with custom settings.

3) Honeywell Home T9 WIFI Smart Thermostat

Many readers have shown faith in Honeywell products for decades. A Honeywell thermostat is a must on any list. But the primary reason to include T9 in the list is its features.

Honeywell Home T9 package includes a power adaptor similar to ecobee. It is a low-voltage alternative to c wire. The option of a power adapter does save a lot of time, money, and makes the installation process easy.

The power adapter is installed on the furnace or heating system. It gives you an option for a C wire that can be connected to the T9 wifi thermostat.

Here are the reasons why you should consider buying T9:

  • Dual-band wifi support.
  • Smart thermostat with smart room sensors so that you can adjust temperature virtually from anywhere.
  • Multi-room Feature: Monitor and set custom temperature for all rooms.
  • Works with Amazon Alexa, Google Assistant, IFTTT, and Cortana.
  • Good sensor range of up to 200ft.
  • Home/Away Scheduling: T9 uses geofencing to understand when you are at home or away. No matter what the schedule is, it saves energy when you are away and switches to your comfort settings when you are reaching home.
  • Monthly power consumption trend reports so that you can save on power bills.
  • Vibrant color touchscreen.
  • Smart Alerts: Get alerts on your mobile when the temperature is beyond the specified limits. Also, get notified when it is time to change the filters.

Concept of C Wire: Why Do We Need C Wire?

The smart thermostat or wifi thermostat is way more feature-rich than traditional programmable thermostats. They have display screens and are connected to your WiFi 24×7. These are power-intensive operations that require a constant power supply.

This continuous power is supplied through c wire also called common wire. A battery-operated thermostat will need a frequent change of batteries. 

The common wire is the best way to power your thermostat. But all is not lost if you don’t see a common wire while replacing your existing thermostat.

Here are a few alternatives that will solve your problem.

C-Wire Alternatives

Thermostat with Power Adapter:

Buy a smart wifi thermostat that comes with a power adapter. The power adapter is connected from one side to the furnace and the other side of the adapter gives your thermostat wires including the c wire.

Unused Wire:

Sometimes luck plays a role and you may find an unused wire rolled and twisted inside when you open your existing thermostat. It is highly recommended you switch off the power before you open it.

A bit of caution before using any unused wire in your current thermostat. An unused wire may be an indication of a c-wire but we suggest you hire an HVAC professional before doing any changes to your wiring.

Power Adaptor:

Most of the latest smart thermostats are bundled with a power adaptor. But if the power adaptor is not part of the package here are a couple of reliable options as a reference.

Venstar Add A Wire

  • Easy to install
  • Easier than running new wire
  • Allows 5 wire thermostats to use only 4 wires
  • Also allows 5 wires to work like 6 wires

Honeywell Power Adapter

  • The C-Wire Power Adapter makes Honeywell Home smart thermostats compatible...
  • Quickly and easily power connected thermostats that require a c-wire.
  • Use for Wi-Fi, 24v Honeywell Home thermostats when a common wire is needed...
  • Easy push terminals and an adhesive mount make installation quick and easy.

Use G Wire as C Wire:

Using G wire as an alternative to c wire is quite common and should be done by a professional. But this solution comes with a disclaimer/compromise. 

As G wire is responsible for fan-only mode, you will lose that functionality. Although the fan will continue to run when the heating and cooling system is in operation.

Before using G wire, make sure your HVAC system is compatible with this arrangement.

Get Common Wire Installed:

Yes, we know this is not an alternative but this is the best solution. Get the C wiring done if you have the budget and time. 

As it is quite evident from this article, the workarounds are good but not a match to the actual common wire. It may be time-consuming and expensive but trust us it is worth the effort. It can save you hassles related to your HVAC system failing at a crucial time.

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