The NEC (National Electrical Code) class 2 identification refers to the output voltage and power capacities of alternating and direct current sources, while the IEC (International Electrotechnical Commission) protection designator, class II, refers to the internal construction and electrical insulation of a power supply. What is a Level 2 Electrician? Level 2 electricians are higher-qualified, meaning they can do more advanced work for customers. They must have received specific training and be in possession of a license to perform Level 2 electrical repairs, maintenance and installations on a wide range of electrical components. This includes aerial and underground electrical work that connects a customer's home or business to an electrical supply network. This is a key difference between level 2 electricians and ordinary operators.
The power of Class 2 and Class 3 circuits is intrinsically limited (so no overcurrent protection is required) or by a combination of a power supply and overcurrent protection. Different circuit conductors: Class 1 circuits can occupy the same cable, housing or channeling regardless of whether the individual class 1 circuits are alternating current or direct current, provided that all of the class 1 conductors are insulated to withstand the maximum voltage of any conductor in the cable, housing or channeling. Due to its power limitations, a Class 2 circuit is considered safe from the point of view of the possibility of causing a fire and offers acceptable protection against electrical shock. Article 725, part III, of the NEC sets the voltage and power limitations for this Class 2 circuit.
The NEC defines a class 2 circuit as the part of the wiring system between the load side of a class 2 power supply and the connected equipment. The maximum circuit voltage is 30 VAC and 60 VDC for a Class 2 power supply limited by overcurrent protection, and 150 VAC or VDC for a Class 3 power supply limited by overcurrent protection. The maximum circuit voltage is 150 VAC or VDC for an intrinsically limited Class 2 power supply and 100 VAC or VDC for an intrinsically limited Class 3 power supply. These circuits are called Class 1, 2 and 3, and should not be confused with Class I, II and III hazardous locations, something completely different.
Generally, class 1 signaling and remote control circuits must meet most of the same wiring requirements for power and light circuits. For more information, read Introduction to Class 1 Circuit Requirements and Class 2 Circuit Requirements. The power supply connected to a class 1, 2, or 3 circuit determines, for the most part, the class of that circuit. Class 1, 2, and 3 circuits are classified as remote control circuits, signaling, and power-limited circuits in the National Electrical Code (NEC).
A class 2 circuit associated with the electrical equipment that is part of a residential oil furnace, for example, usually receives energy from a 24 V transformer whose primary is connected to a 120 V branch circuit in the installations. Class 1 signaling circuits are used in hospital nurses' call systems, electric clocks, bank alarm systems, and factory call systems. The main differences in the installation of class 2 cabling are that 18 and 16 AWG conductors are allowed and that joints, for example with nuts, are allowed outside conventional housings. Room thermostats, water temperature control devices, and other similar controls used in conjunction with electrically controlled home heating and air conditioning are not considered safety control equipment and are therefore not class 1.