Eleanor Finch
The National Electrical Code (NEC) is a set of guidelines that outlines the requirements for electrical installations in the United States. One of the key areas addressed by the NEC is the use of disconnecting means, which are mechanisms that allow for the interruption of power to a circuit or equipment. While the NEC provides specific instructions for lockable disconnecting means, there has been some ambiguity and discussion around whether breakers can be locked in the closed (on) position. Electrical professionals have debated the safety implications of locking disconnects in the on position, particularly in emergency situations where quick de-energization is necessary. However, interpretations of OSHA regulations suggest that there is no explicit prohibition against locking disconnecting means in the closed position, as long as accessibility requirements are met. The NEC has also introduced changes over the years, consolidating and clarifying the requirements for lockable disconnecting means, but it does not explicitly forbid locking breakers in the closed position.
| Characteristics | Values |
|---|---|
| Disconnecting means | Should be capable of being locked in the open position |
| Disconnecting means | Should be capable of being locked in the closed position |
| Disconnecting means | Should be capable of accepting a lock in the on position |
| Disconnecting means | Should be capable of accepting a lockout device |
| Disconnecting means | Should be installed on or at the switch or circuit breaker |
| Disconnecting means | Should be located within sight of the appliance |
| Disconnecting means | Should be located within 50 feet of the motor |
| Disconnecting means | Should plainly indicate whether it is in the open or closed position |
| Disconnecting means | Should be installed at a readily accessible location |
| Disconnecting means | Should be lockable only in the open position |
| Disconnecting means | Should be lockable in the on position |
| Disconnecting means | Should be lockable in the off position |
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What You'll Learn
The NEC does not prohibit locking the device on
The National Electrical Code (NEC) is a document that outlines the requirements for electrical installations in the United States. One of the key areas addressed by the NEC is the use of disconnecting means, which are mechanisms that allow for the disconnection of electrical power in the event of an emergency or for maintenance purposes.
While the NEC provides detailed guidelines for the use of lockable disconnecting means, there is no explicit prohibition against locking a device in the "on" or closed position. This means that, in general, it is not against the NEC to lock a device in the closed position. However, it is important to consider the specific circumstances and requirements of the installation.
For example, in certain situations, it may be necessary to have easy access to a disconnecting means in case of an emergency. In such cases, locking the device in the closed position could impede access and create a safety hazard. Therefore, while not explicitly prohibited by the NEC, locking a device in the closed position should be carefully evaluated to ensure it does not compromise safety or accessibility.
Additionally, the NEC has specific requirements for lockable disconnecting means in certain situations. For instance, the 2014 edition of the NEC introduced a new section in Article 110, which consolidates the requirements for lockable disconnecting means across various sections of the code. This section specifies that when a disconnecting means is required to be lockable open, it shall be capable of being locked in the open position, and the provisions for locking shall remain in place with or without the lock installed.
Furthermore, the NEC also addresses the use of fused disconnects, which can be locked in either the open or closed position. While the code allows for this flexibility, it is important to consider the potential safety implications, especially for disconnects needed for motors, AC, and other equipment. In an emergency, the inability to shut off a particular piece of equipment could pose a risk.
In summary, while the NEC does not explicitly prohibit locking a device in the closed position, it is important to carefully consider the specific circumstances and requirements of the installation. The NEC provides detailed guidelines for the use of lockable disconnecting means, and safety and accessibility should always be paramount considerations.
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Disconnects required for motors, AC, etc. cannot be locked in the on position
While there is no explicit prohibition against locking disconnects in the "on" position, there are safety concerns to consider. Disconnects required for motors, AC, and other applications should be easily accessible in case of emergencies. If a disconnect is locked in the "on" position, someone may be unable to shut off the equipment, potentially leading to hazardous situations.
The National Electrical Code (NEC) has specific requirements for lockable disconnecting means. While the code allows locking in the "on" position in certain cases, it emphasizes the importance of accessibility. According to the code, disconnecting means should be "readily accessible," which means they can be quickly reached and operated without obstacles. This suggests that locking disconnects in a way that hinders accessibility should be avoided.
Additionally, the NEC has introduced changes to consolidate and clarify the requirements for lockable disconnecting means. Section 110.25 of the NEC now serves as the central reference for these requirements. This section states that when a disconnecting means is required to be lockable open, it shall be capable of being locked in the open position, and the provisions for locking should remain in place with or without the lock installed. This ensures that even without a lock, the disconnecting means can be secured in the open position.
It's worth noting that some disconnects, such as those for fire pumps, may require locking in the "on" position. In such cases, the location of the key must be posted or easily accessible. However, for disconnects needed for motors, AC, and similar applications, the primary concern is often the ability to quickly shut off equipment in an emergency. Therefore, while locking these disconnects in the "on" position may be technically possible, it is generally discouraged to prioritize safety and accessibility.
To summarize, disconnects required for motors, AC, and similar equipment should not be locked in the "on" position to ensure accessibility and safety in emergencies. While locking these disconnects may be permissible in certain cases, it is generally advisable to avoid this practice to prevent potential hazards and comply with the spirit of the NEC's accessibility requirements.
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Fire pump disconnects can be locked in the on position
Disconnects that require locking in the on position include those for fire pumps, as well as those for hand dryers at rest stops, and condensers in residential areas. These disconnects are not EPO switches, so they can be locked in the on position.
However, locking a disconnect in the on position may pose a safety issue in certain situations. For instance, if there is an emergency and someone is unable to shut off a particular piece of equipment, having the disconnect locked in the on position could be problematic.
According to electrical professionals, locking the breaker switch in the on position will not affect its overload or overcurrent operation, and the breaker will still trip. Nonetheless, if the breaker serves as a disconnecting means that must be readily accessible, the lock may need to be removed first.
In terms of specific disconnect switches, Siemens VBII disconnect switches can be modified to be locked in the closed position. Similarly, Square-D Disconnect Switches (or Safety Switches) can be modified by drilling a hole to allow locking in the closed position without violating UL or other ratings.
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The disconnecting means shall be a listed device
The National Electrical Code (NEC) is a set of safety standards for electrical installations in the United States. It outlines regulations regarding the marking of service disconnecting means. Service disconnect devices are critical components designed to safely disconnect the electrical supply from a building during maintenance or emergencies.
Per NEC Section 230.70 of 2020, the building service disconnect switch should be located outside or inside the building closest to the entry point of the service conductor. The service disconnect is the largest circuit breaker in the box and is sometimes called the "electrical main".
In the case of permanently connected appliances rated over 300 volt-amperes, the branch-circuit switch or circuit breaker can serve as the disconnecting means if it is within sight of the appliance or is lockable in accordance with 110.25. The provision for locking or adding a lock to the disconnecting means shall be installed on or at the switch or circuit breaker and shall remain in place with or without the lock installed.
Additionally, the disconnecting means should be readily accessible to the operator and provided with a sign to identify the location of the supply-side overcurrent protective device.
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The 2014 NEC added a section on lockable disconnecting means
The National Electrical Code (NEC) is a document that outlines the requirements for electrical installations in the United States. In 2014, a new section was added to the NEC regarding lockable disconnecting means. This change was made to simplify the code and improve safety.
Prior to the 2014 update, the NEC required that any section that allowed a remote disconnecting means to be lockable in the open position must specify the provision for locking or adding a lock. This meant that the same repetitive code language was found in multiple locations within the codebook. The 2014 update introduced a new section, 110.25, which consolidates the requirements for lockable disconnecting means into a single location.
Section 110.25 states that when a disconnecting means is required to be lockable open, it must be capable of being locked in the open position. This provision for locking shall remain in place whether the lock is installed or not. This change simplifies the code by allowing users to refer to a single section for the rules on lockable disconnecting means, rather than searching through multiple sections with repetitive language.
It's important to note that this update does not introduce new locking provisions. The specific locking provisions have existed in previous versions of the NEC, such as the 1999 and 2002 editions. However, the 2014 update standardized the language and made it more consistent across the code.
The addition of Section 110.25 also has implications for permanently connected appliances rated over 300 volt-amperes. In these cases, the branch-circuit switch or circuit breaker can serve as the disconnecting means if it is within sight of the appliance or is lockable in accordance with 110.25. This provides clarity and flexibility for installers and helps ensure safety and compliance with the NEC.
While the NEC does not explicitly prohibit locking a breaker switch in the on position, there are safety considerations to take into account. In an emergency, it may be crucial to shut off a particular piece of equipment, and having it locked in the on position could pose a potential risk. Therefore, it is recommended to refer to specific guidelines, such as 240.24, to determine whether locking the breaker in the on position is appropriate for a given situation.
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Frequently asked questions
NEC stands for National Electrical Code.
A breaker locked in the closed position will still trip in the event of an overload or overcurrent.
The NEC does not prohibit locking switches in the closed position. However, it is important to consider the purpose of the breaker and whether it is serving as a required disconnecting means that needs to be readily accessible.
A disconnecting means is a switch or circuit breaker that can be used to disconnect power from an appliance or piece of equipment.
Yes, in certain situations, such as with life support equipment or in an industrial facility with maintenance personnel, locking a breaker in the closed position may be beneficial to prevent accidental disconnection.
