A thermostat cable is often used in an HVAC and other low voltage systems. First of all, you need to know the type of thermostat cable you need. The following are the options available to you:
24V
110/240V
Millivolt thermostat
This article covers 24V systems. A low voltage or 24V cooling and heating system includes one or more of the following components:
Heating: heat pump, gas furnace, oil furnace
Cooling: heat pump, PTAC, air conditioner
Accessories: ERV/HRV, humidifier, dehumidifier and air quality equipment such as air purifier
These systems can be split systems, ductless split systems and package systems. Low voltage 24V HVAC systems are the most common.
Wire a Thermostat
Replace Thermostat Cable
Take the following approach if you want a new thermostat:
Turn the circuit off.
Take a photograph of all connections and wiring.
Remove one wire at a time from the old thermostat and connect to the new thermostat.
Plug the power cable in and turn the circuit on.
It should work perfectly. If it does not, turn the circuit off and call the HVAC company’s customer support department.
Locate Connections in the Air Handler or Furnace
Your job gets a little complex after removing the thermostat. Take the following approach:
Turn the circuit off.
Uncover the air handler or furnace.
Locate from where the bundle of three to eight wires enters the furnace.
Take a photograph of the connecting terminals.
Wire the thermostat according to the photo.
Turn on the circuit.
It should work. In case it does not, turn the circuit off, cover everything and call the customer support representative of your HVAC company.
Use Standard Wiring Colors
In case the thermostat is already removed, you can use standard wiring colors. Take the following steps:
Connect the red wire with the R terminal.
Connect the green wire with the G terminal.
Connect the white wire with the W terminal.
Connect the yellow wire with the Y terminal.
Connect the blue wire with the C terminal.
Adding Thermostat C Wire
This wire carries a constant power supply to the thermostat. The thermostat constantly monitors climate features such as indoor temperature to create precise indoor comfort. Many thermostats pull power from the red wire to function without a C wire. In case C wire is required, keep reading. You have several options if you need to remove the old thermostat and no wire attached to the C terminal.
You can use a thermostat that does not require a C wire. However, you will get imperfect results.
You can use an unused wire as a C wire.
You can use G wire as a C wire.
You can install a jumper or splitter approved by your thermostat brand.
In the end, you can call a professional for installation.
When it comes to choosing a thermostat cable for your HVAC system, learn about the standards and guidelines. There are many online suppliers selling thermostat cables. Buy from one who sells high-quality thermostat cables.'