When you have to install a new doorbell at your house, you have to decide what wiring to use. If you have different types of wire available in your home’s storage room you are challenged to make the right decision regarding what wire to use.  

Generally, there are thermostat wires left after your smart thermostat has been installed, but you don’t want to damage the doorbell system or your home’s electrical wiring by using wires that are not fit for the job. You now wonder whether you can use your extra thermostat cable to wire your new doorbell.

Thermostat wire can safely be used to wire your doorbell as long as it is a 15, 16, or 24-volt doorbell system.  About 99% of domestic door chimes are low voltage appliances and can be wired with a thermostat cable. Thus, you can almost always use a thermostat cable to run to the push button.

We’ll briefly discuss why a thermostat cable can be used and also indicate when you should not use a thermostat cable in your doorbell system.

Why you can use a thermostat wire?

  • You’ll rarely need more than an 18-2 thermostat cable to run to the pushbutton of a doorbell. Thus, your available thermostat wire is ideal for this. 
  • Thermostat wires are solid copper wires and they are also well-insulated.  All thermostat cables are covered with tough plastic sheathing as insulation. 
  • A thermostat wire is also very durable. It is designed to be hard to damage. 
  • The wires are ideal for in-wall applications like doorbells. 
  • You can also use thermostat wires in extreme direct sunlight and other extreme temperature exposure ranges. 
  • As a thermostat cable is a solid copper wire, it is always a good choice for all structural wiring, such as for doorbells. As it is made of solid copper you can tightly hook it around the screw terminals of the doorbell system. 
  • Solid copper can also easily be twisted together to fit tightly on the terminals.  As long as you ensure that the screws stay firmly tightened, the solid copper wire will not come loose after installation. 

When not to use a thermostat cable

Although a thermostat wire is normally being rated for up to 150 volts, you must never use a thermostat cable for 120-240 volt applications. The indication of “150 volts” on the cable only means that the low voltage wire will not melt if exposed to 120 volts. 

You must remember that apart from the safety risk when you use a thermostat able for 120-240 volts appliances, the electrical code in most countries prohibits the use of low voltage structural wires for carrying household power.  

Some things to remember

If your doorbell is equipped with a chime playing a tune, you need an extra wire to the transformer to allow the chime unit to operate. When the bell is pressed the tune starts to play, but must keep on playing after the bell button has been released again. 

When you have the correct wire, you must ensure that you connect the wires correctly. The terminals on the buzzer or bell are commonly labeled “F”, “R”, and “C”. The important connection is the one to “C”. The “C” stands for “common” and should be tied to one of the screw terminals coming out of the transformer. 

There are videos available showing how to install a doorbell.


You can use a thermostat cable to wire your doorbell system, as it is meant to be used in extreme weather conditions and is well-insulated. To a great extent, it is better to use thermostat cables than phone cables, and even cable marked as “bell wire.”


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