A Class 2 transformer is one that delivers 100VA or less with a maximum output voltage of 30VAC or less. They are used in applications ranging from air conditioning thermostats, garage door openers, sprinkler system controls, digital controllers, gas controls, ignition systems, motor actuators, staging controls, the food and beverage industry and most other Heating, Ventilation, Air Conditioning, and Refrigeration (HVACR) control systems.
Class 2 transformers are known as low voltage transformers because they are designed to produce a low voltage output, typically under 30 volts, with limited power, making it safer to use in applications where reducing the risk of electric shock is crucial, like control circuits, doorbells, and low-voltage lighting systems; essentially, it provides a low-power, low-voltage supply to a “Class 2 circuit” as defined by electrical safety standards.
Their low voltage output means they are considered safer than other transformers because the low secondary voltage reduces an electrical shock hazard, and the low power output reduces a fire hazard. The current is also limited either by a fuse or by the internal impedance of the SEC winding (known as inherently limited).
The current limiting factor is crucial in their safety….when limited by their internal impedance they are known as “inherently limited”….basically the winding inductance is such that given an applied PRI voltage the current in the winding is not enough to start a fire…a “non-inherently limited” transformer relies on an internal fuse to blow when a certain temperature is reached….
We here at CET can help with your Class 2 transformer needs!
Frequently Asked Questions
What is a Class 2 transformer?
A Class 2 transformer is a low-voltage power transformer that is limited to a maximum output of 100VA and 30VAC.
These low-voltage transformers comply with UL5085-3 safety standards and are designed for applications that require safe and limited power output.
When would a Class 2 transformer be used?
Class 2 transformers are used in low-voltage applications where standard line voltage (120VAC in the USA) is too high.
Common applications include HVAC systems, lighting systems, garage door openers, and other devices that typically operate at around 24VAC.
Why are Class 2 transformers considered safer?
Class 2 transformers are designed so that under normal and fault conditions, the output power remains limited enough to prevent fire ignition.
The lower voltage levels also reduce the risk of electric shock, often eliminating the need for additional overcurrent protection.
What is the difference between Class 1 and Class 2 transformers?
Class 1 transformers operate at higher voltages and power levels and therefore require stricter wiring methods and additional protection.
Class 2 transformers operate at lower voltages and limited power levels, allowing for reduced wiring requirements and improved inherent safety.
What is the difference between Class 2 and Class 3 transformers?
Class 3 transformers operate at higher voltages than Class 2 transformers but lower voltages than Class 1.
Class 3 systems typically have a maximum output rating of 100 VA.
Although Class 3 transformers are considered safe from fire ignition, only Class 2 transformers are designed to protect against both electric shock and fire hazards.