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Class 1 circuits are commonly used for remote control, signalling, and power-limited applications. They are defined as the portion of the wiring system between the load side of the overcurrent protection device (OCPD) or the power-limited supply and the connected equipment. Class 1 circuits are further divided into two subgroups: power-limited and remote-control and signalling circuits. Power-limited Class 1 circuits are limited to 30V and 1000VA, while remote-control and signalling circuits are limited to 600V. These circuits are used in a variety of applications, including motor controllers, elevators, and hospital nurse call systems.
| Characteristics | Values |
|---|---|
| Definition | The portion of the wiring system between the load side of the overcurrent device or power-limited supply and the connected equipment |
| Types | Power-limited and remote-control and signaling circuits |
| Power-limited Class 1 circuits | Limited to 30V and 1000VA |
| Class 1 remote-control and signaling circuits | Limited to 600V |
| Minimum size of conductors | 14 AWG |
| Permitted size of conductors | 18 and 16 AWG |
| Uses | Motor controllers, elevators, conveyors, equipment controlled from remote locations, nurse call systems, electric clocks, bank alarm systems, factory call systems, security systems, control circuits for motors, lighting dimmer systems, computer network systems, access control circuits |
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What You'll Learn
Class 1 circuits are part of the wiring system
Class 1 circuits are indeed part of the wiring system, specifically defined as the portion of the wiring system between the load side of the overcurrent protection device (OCPD) or the power-limited supply and the connected equipment. They are commonly used for remote control, signalling, and power-limited applications.
Class 1 circuits are further divided into two subgroups: power-limited and remote-control and signalling circuits. Power-limited Class 1 circuits have a critical function: they limit the output-side of the circuit to a maximum of 30 volts and 1000 Volt-Amps (VA). This voltage restriction is an essential safety measure, as higher voltages could lead to electrical shocks.
The second subgroup, remote-control and signalling circuits, have a broader voltage range, allowing up to a maximum of 600 volts. These circuits are commonly used in motor controllers, elevators, conveyors, and equipment controlled from remote locations. They are also found in hospitals for nurses' call systems, electric clocks, bank alarm systems, and factory call systems.
It's important to note that Class 1 circuits are susceptible to damage from their environment. Any failures to the circuit, cables, or box could potentially cause fires or other life-threatening hazards to nearby individuals. Therefore, remote-control systems classified as Class 1 must be enclosed to prevent damage to the surrounding area and protect the circuit itself.
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Power-limited Class 1 circuits
Class 1, 2, and 3 circuits are commonly used for remote control, signalling, and power-limited circuits. The National Electrical Code (NEC) defines these circuits as the portion of the wiring system between the load side of the overcurrent protection device (OCPD) or the power-limited supply and all connected equipment.
Class 1 circuits are divided into two types: power-limited and remote-control and signalling circuits. Power-limited Class 1 circuits are limited to a maximum output of 30 Volts and 1000 Volt-Amps (VA). They are equipped with overcurrent protection, which restricts the amount of supply current on the circuit in the event of an overload, short circuit, or ground fault.
To comply with the 1000 Volt-Ampere limit, non-transformer sources must have a maximum output of 2500 Volt-Amps, with the product of maximum current and voltage not exceeding 10,000 Volt-Amps. Transformers supplying power to Class 1 circuits must comply with Article 450 regulations.
Class 1 power-limited circuits are commonly used in security systems. They are considered safe from a fire initiation standpoint and provide acceptable protection from electric shock.
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Remote-control and signalling circuits
Class 1, 2, and 3 circuits are classified as remote-control, signalling, and power-limited circuits in the National Electrical Code (NEC). The NEC defines such circuits as the portion of the wiring system between the load side of the overcurrent protection device (OCPD) or the power-limited supply and all connected equipment.
Class 1 power-limited circuits have a current limiter on the power source that supplies them. This limiter is an OCPD that restricts the amount of supply current on the circuit in the event of an overload, short circuit, or ground fault. A transformer or other type of power supply supplies power to Class 1 circuits.
Class 1 remote-control and signalling circuits are limited to 600 volts, but there are limitations on the power output of the source. They must meet most of the same wiring requirements for power and light circuits. They are commonly used in motor controllers (which operate mechanical processes), elevators, conveyors, and in equipment controlled from one or more remote locations.
Class 1 signalling circuits are used in nurses' call systems in hospitals, electric clocks, bank alarm systems, and factory call systems. Conductors of different circuits can occupy the same cable, enclosure, or raceway without regard to whether the individual Class 1 circuits are AC or DC, provided all the Class 1 conductors are insulated.
To limit the spread of fire or products of combustion, the installation of Class 1 and Class 2 circuits must comply with specific regulations. Electrical circuits and equipment must be installed in such a way that the spread of fire or products of combustion is not substantially increased. Openings into or through fire-resistive walls, floors, and ceilings for electrical equipment must be fire-stopped using approved methods to maintain the fire-resistance rating of the assembly.
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Class 1 circuits and fire hazards
Electrical fires can be catastrophic, causing significant damage and threatening lives and properties. According to the National Fire Protection Association, there are an estimated 33,470 commercial electrical fires each year in the United States, resulting in around 45 deaths and $1.36 billion in direct property damage.
Class 1, 2, and 3 circuits are classified as remote-control, signalling, and power-limited circuits in the National Electrical Code (NEC). The NEC defines such circuits as the portion of the wiring system between the load side of the overcurrent protection device (OCPD) or the power-limited supply and all connected equipment. These circuits are characterised by their usage and electrical power limitations, differentiating them from light and power circuits.
Class 1 circuits are further divided into two types: power-limited and remote-control and signalling circuits. Power-limited Class 1 circuits are limited to 30 volts and 1000 volt-amps (VA). They are equipped with overcurrent protection to restrict the supply current in the event of an overload, short circuit, or ground fault. Remote-control and signalling circuits, on the other hand, are limited to 600 volts, with limitations on power output. These circuits are commonly used in motor controllers, elevators, conveyors, and equipment controlled from remote locations.
While Class 1 circuits have specific voltage and power limitations, it is important to note that they are not immune to fire hazards. Electrical fires can occur due to various factors, including damaged wiring, malfunctioning appliances, overloaded circuits, faulty outlets, and defective lighting fixtures. Proper installation, maintenance, and adherence to safety protocols are crucial to mitigate the risk of fire associated with any electrical circuit, including Class 1 circuits.
To enhance safety and prevent electrical fires, it is recommended to regularly inspect electrical systems and equipment for wear or damage, promptly repairing or replacing any faulty components. It is also essential to avoid overloading circuits with too many devices and to ensure proper usage of extension cords and power strips. Additionally, providing staff training and establishing evacuation plans can help mitigate the impact of electrical fires in commercial and industrial settings.
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Class 1 circuits in commercial and industrial settings
Class 1, 2, and 3 circuits are classified as remote-control, signalling, and power-limited circuits in the National Electrical Code (NEC). The NEC defines such circuits as the portion of the wiring system between the load side of the overcurrent protection device (OCPD) or the power-limited supply and all connected equipment. These circuits are characterised by their usage and electrical power limitations, which differentiate them from light and power circuits.
The NEC divides Class 1 circuits into two types: power-limited and remote-control and signalling circuits. Power-limited Class 1 circuits are limited to 30V and 1000VA. They have a current limiter on the power source that supplies them. This limiter is an OCPD that restricts the amount of supply current on the circuit in the event of an overload, short circuit, or ground fault. A transformer or other type of power supply supplies power to Class 1 circuits.
Class 1 remote-control and signalling circuits are limited to 600V, but there are limitations on the power output of the source. These circuits must meet most of the same wiring requirements for power and light circuits. They are commonly used in motor controllers (which operate mechanical processes), elevators, conveyors, and in equipment controlled from one or more remote locations. Class 1 signalling circuits are used in nurses' call systems in hospitals, electric clocks, bank alarm systems, and factory call systems.
Class 1 circuits are used in a variety of commercial and industrial settings. Commercial/industrial electrical systems, for example, may include ground-fault circuit interrupters (GFCI) for specific appliances and the use of "replacement panelboards". They may also feature arc-fault circuit interrupter (AFCI) protection in the sleeping areas of public safety and first responder facilities.
Additionally, the NEC addresses electrical installations in commercial and industrial settings, including hazardous locations within commercial and industrial cannabis production facilities. The 2023 edition of the NEC represents a significant revision to modernise the code and reflect the rapidly evolving electrical landscape.
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Frequently asked questions
A Class 1 electrical circuit is a part of the wiring system that interfaces the load-side of power-limiting equipment and any connected equipment.
Class 1 circuits are divided into two subgroups: power-limited and remote-control and signaling circuits.
A common example of a Class 1 remote-control circuit is in motor controllers, which are used in elevators, conveyors, and equipment controlled from remote locations.
