How Do Transformers Work in HVAC Units?

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What does HVAC mean?

The term HVAC first needs to be understood. This term stands for Heating, Ventilation and Air Conditioning. Older heating units from the 1950s through to the late 1970s were generally a simple unit that consisted of a heater only. When the thermostat called for heat a burner was ignited, the fan started and it heated the area that was being controlled. Today there are small microprocessors or computers that monitor and control the entire process for heating and cooling. The primary controlling device for HVAC units is the thermostat.

Thermostats control the temperature in our home and work environments. The thermostat is fed power from the HVAC unit by a step down transformer into a voltage that is safe for the exposed environment the thermostat is placed.

How Much Power Does an HVAC System Require?

The general low voltage of the thermostat is 24 volts or less depending on the HVAC unit. This voltage is transformed to a lower voltage generally from 120 volts or 240 volts AC, alternating current. Some units will also use a DC, direct current for a safer and more accurate control signal. The transformer used for DC control is also known as a regulated DC power supply. As the power signal is a steady current or voltage. This low voltage will also control the operation of the motors contactors to switch the circulation fan and air conditioning compressor on and off.

How Does an HVAC System Manage Energy Surges?

Some HVAC units will utilize what is known as a voltage regulator transformer. This transformer helps to condition the incoming voltage from any spikes that can occur in the power. You may notice these spikes when a light bulb may seem a little brighter or the power will just go off for a second or blinks. The voltage regulator transformer aids in smoothing out the spikes so it will not damage the internal circuitry used for controlling the HVAC unit.

How is Heating Accomplished?

Heating your home is accomplished by burning fuel, natural gas, propane or fuel oil or the use of electrical resistance coils to produce the heat. Older gas or fuel oil burners require a spark to ignite the fuel source. This spark is created by a step up transformer. This particular transformer can generate a voltage in the thousands of volts, generally in the range of 3000 to 8000 volts, depending on the unit. Electrical resistance heaters do not require a transformer as they use the line voltage to energize the heating coils.


G.K. Bayne

G.K. Bayne is a freelance writer for various websites, specializing in back-to-basics instructional articles on computers and electrical equipment. Bayne began her writing career in 1975 and studied history at the University of Tennessee.