How To Pick The Right Thermostat For Your Home?

Thermostats are not easily interchangeable to any furnace. Some thermostats are designed to work best on a certain type of furnace, while some are just simply not compatible. Having to use a mismatched thermostat can result in an under- or over-heated home, hence your home’s level of comfort lowered. It can also affect your furnace’s efficiency and performance and can even cause damage to it in the long run.

While there is a long list of thermostats available in the market, there is also a wide variety of heating systems to match it on. So choosing a thermostat for your furnace can be an overwhelming (but important) decision to make, especially when your family’s comfort and safety is on the line.

In this blog, we will talk about the three main types of thermostat systems and its compatible furnace or heating/cooling systems.

Types of Thermostats

Low-voltage Thermostats

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Low-voltage thermostats, because of its high functionality and adaptability, are the most prevailing type of thermostat in the market and in residential homes today.

Low-voltage thermostats are named as such because they use a step-down transformer (usually mounted on or near the furnace) that reduces the household line voltage from the regular 120 volts to lower voltage that is commonly between 12 and 24 volts.

Most low-voltage thermostats are run on 24 volts, though some may run on voltages as low as 6 volts and as high 30 volts. Voltages may totally vary depending on your home’s heating system type, brand or model.

One way to recognize a low-voltage thermostat is its very thin wires.

Voltage: 24 volts (most common)

Number of Wires:

  • 2 or 3 without air conditioning unit
  • 4 or 5 with an air conditioning unit
  • 7 or more wires with heat pump systems

Kinds of Thermostats:

  • Digital and Programmable Thermostats
  • Mercury Bimetallic Thermostats
  • Mechanical Contact Thermostats

Best Used In:

  • Gas forced-air furnaces
    • Standing pilot furnace
    • Electronic ignition furnaces
  • Electric forced-air furnaces
  • Single and multi-stage heat pumps
  • Gas-fired, oil-fired, and electric hot water boilers for radiant heat or baseboard hydronic systems
  • Electric central air conditioning systems

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Line-voltage Thermostats

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Unlike low-voltage thermostats that need a step-down transformer and run on a low voltage circuit, line-voltage thermostats run directly on the standard residential line voltage of 120 volts AC or 240 volts AC.

Aside from the running voltage difference between low-voltage and line-voltage thermostats, there is also a little disparity on its functionality. Line-voltage thermostats are not as sensitive in sensing indoor temperature as compared to low-voltage thermostats. It needs at least 7 degrees Fahrenheit of temperature change before a line-voltage thermostat can respond and command your HVAC unit to turn on or shut off. Thus, in homes where the indoor temperature is controlled by this type of thermostat, wider temperature fluctuations are experienced.

To identify a line-voltage thermostat, you can visually check its wires which are usually thick, 12-gauge or 14-gauge wires.

Voltage: 120 volts or 240 volts (standard home line voltage)

Number of Wires:

  • 2 or 4

Best Used In:

  • Electric resistance heating systems
    • Electric baseboard heaters
    • In-wall heaters
  • Localized heating systems (with a line-voltage thermostat in each room)
  • Oil-fired hot water boilers for radiant heat or baseboard hydronic systems

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Millivolt Thermostats

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Millivolt thermostat systems are the least common type of thermostats found in residential homes today. Home heating systems that use this kind of thermostats have a special voltage requirement that can’t be addressed by both low-voltage and line-voltage thermostats.

As it is named, millivolt thermostats use very low voltages. Millivolts thermostats run in only 0.75 volts or 750 millivolts but because it is self-powered and is and not wired together with the household wiring system, it does not need a step-down transformer, unlike low-voltage thermostats, to operate.

Voltage: 0.75 volts or 750 millivolts

Number of Wires:

  • 2

Best Used In:

  • Gravity wall (room) furnaces
  • Direct-vent or top-vent wall furnaces for small areas
  • Mobile home direct-vent wall furnaces

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To know which type of thermostat you currently have at home, you can visually inspect the number or types of wires used or check the voltage listing inside the cover of the thermostat or in your heating system itself and countercheck it with the details of each thermostat type mentioned above.

Do not let your family and your pocket suffer over a mismatched thermostat. Should you need a new thermostat, HVAC parts, accessories, and supplies, check out and use this coupon code IQK5657F6I to get $5.00 off your order total!

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