What is the Difference Between a Line Voltage Thermostat and a Low Voltage Thermostat?
The type of thermostat you have is important to know in case you need to upgrade or replace it. The first thing you need to know is your current thermostat's voltage.
About Voltage Types
What is Line Voltage?
Line voltage, or high voltage, wiring operates at ranges between 120 volts and 240 volts of electricity. Large amounts of electricity run through your home supplying power to every area connected to the main circuit.
Most homes use high voltage circuits throughout. Line voltage systems powers common household items such as light fixtures, vacuum cleaners, ceiling fans, blenders, or coffeemakers.
Advantages of Line Voltage:
- Lower cost of appliances and fixtures
- Plug and Play, easy to install appliance
- Does not require transformer to convert voltage
- Large variety of products to choose from use it
- Standard line voltage for American products
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What is Low Voltage?
The National Electrical Code (NEC) defines low voltage wiring as any wiring system operating at 50 volts or less. You can find low voltage in smaller appliances and entertainment systems.
For tools or appliances, most low voltage equipment operates at 12V, 24V, or 48V. Over a long period, low voltage wiring increase energy savings by reducing energy consumption.
Low voltage electric systems include:
- Doorbells: Low voltage wires power most standard and smart doorbells.
- Garage Openers: Powers the operating motor controls that lift and lower your garage door.
- Thermostats: Connects thermostats and HVAC units to control indoor temperatures.
- Landscape Lighting System: Lights up outdoor stake and pathways lights, adding visibility and security.
- Fire Alarms: Keeps powered connection for fire alarm detection.
- Security Systems: Operates cameras, sensors, alarms, and surveillance technology in home and commercial areas.
Low voltage equipment typically requires a transformer to reduce the line voltage down to the applicable voltage. This makes the initial cost higher and the installation a bit more difficult.
What is a Line Voltage Thermostat?
A high voltage thermostats does the opposite of a low voltage, as it directly connects your main electrical circuit, thermostat, and heaters. Line voltage models see most use in radiant, resistive heat, and convection heating units. These types of systems include fan-forced, in-ceiling radiant, cove, direct-wired furnace, wall and baseboard heaters.
A line voltage thermostat control the length of time each heater stays on to manage room temperature. They are quick and easy to install and operate using 120V-240V on average.
A line voltage thermostat uses 2 or 4 thick wires depending on if it is Single or Double Pole model:
- Single-Pole: 2-wire connection to the main circuit and does not have a true off setting.
- Double-Pole: 4-wire connection to the main circuit and can completely cut power to the heater.
What is a Low Voltage Thermostat?
In most cases, low voltage means the thermostat operates between 12 and 24 volts of electricity. Low volt thermostats control your HVAC system by signaling the unit to turn OFF or ON, offering indirect heating.
As the most common type, low voltage thermostats control many types of central HVAC systems. These systems include heat pumps, furnaces, air conditioning, split systems and boilers.
LV thermostats have multiple thin wires connect to them depending on the needs of the system:
- 2-3 wires in systems without cooling
- 4-5 wires in systems with cooling
- 7+ wires in systems with heat pumps
Some low voltage thermostats can be more difficult to install and have as many as nine wires.
Line Voltage vs Low Voltage Thermostats?
Low voltage thermostats do not directly control the heater, instead they send signals to control what the heater does.
On the other hand, line voltage thermostats directly connect lines of electricity between your thermostat and heater. Then, the heating element converts the high voltage current into space heating.
If you can't tell the difference between the two, do the following:
- What type of HVAC system do I have? Low voltage T-stats control ducted or radiator central HVAC systems using 1-2 thermostats in the home. Electric HVAC uses many thermostats (one per room) and requires a line voltage connection.
- What voltage is my thermostat? Check the labeling of your thermostat. Most United States building codes require clear labeling of HIGH VOLTAGE items with a warning or voltage listed. If there is no label on your thermostat, you can also verify the voltage using a voltmeter. Consult a professional for any electrical work.
- How many wires connect my thermostat? Inspect the number of wires leading to your t-stat. Thin, multi-colored wires pushed through drywall usually means low voltage. Line voltage models run 2 or 4 grouped wires to electrical boxes.
- How thick are my thermostat wires? The smaller the wires, the more likely it is a low voltage install. Only thick wiring can safely carry high 120 or 240 voltages.
Which Thermostat Do I Need?
If you are not sure, it is always best to have a certified technician confirm this for you. A technician will tell you what you have and the cost of each option. Find the right thermostat for you here!
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