For the past several years the Knox Company has been working on the concept and development of an emergency electrical shutdown box. Given the hazards to firefighters when attempting to shut down electrical power for tactical operations, this product is long overdue. This has proven to be a daunting process given the requirements of the industry, the fire service, and UL. The 4500 is effectively a Listed Allen-Bradley switch mounted inside an approved NEMA container. This switch and container are then secured into a Listed Knox Vault that has been modified to meet the requirements of UL. Our engineers have written the article below to help fire officials understand our design parameters and the intended usages. The Knox 4500 Series recently passed all of the testing criteria of UL and is now fully Listed, and is currently being used in many jurisdictions.
Larry Pigg
Director of Public Affairs
In recent years, there has been a noted increase in firefighter injuries related to
attempts to shut off power in large structures. In responding to calls where electrical hazards are present, fire crews must wait for city electricians to come to the scene and cut power before entering. The sooner the power can be shut off, the quicker the fire can be put out and the less damage is done.
In some jurisdictions, the response of fire officials has been the adoption of a requirement in the National Electrical Code (NEC) 230.205 Disconnecting Means which requires a high-voltage service disconnect to be located “outside and within sight of, or inside nearest the point of entrance of, the service conductors” of the building or structure being supplied. This requirement is not currently part of the fire code, but both the International Code Council (ICC) and the National Fire Protection Association (NFPA) are discussing the development of codes for fire protection that would require external shunt trip controls on structures where exposure to high-voltage is a risk.
Many jurisdictions are adopting these requirements early, however, before now no product has been commercially available to meet the needs of this application. Building owners have therefore resorted to their own solutions. In many cases, standard off-the-shelf outdoor enclosures have been used to house push buttons, mushroom switches or key switches that are wired into a shunt trip circuit.
The difficulty with this approach is that any enclosures used for this application must meet UL requirements for housing industrial control switches (UL508, now transitioning to UL60947-1). Most commercially available electrical enclosures meeting these requirements lack the necessary security to be used as an emergency shunt trip station. An emergency shunt trip station must be adequately protected against an attack with the intent to cause an unauthorized shut down event which could cause damage to sensitive systems and incur considerable expense in lost time, data corruption, or system restart costs.
The switch can be tagged with breakaway tamper seals
Fire officials have turned to the Knox Company to develop a box that will meet the needs of first responders. The Knox® 4500 Remote Electrical Power Shutdown Station is a derivative of the 4400 Knox-Vault® making it a highly trusted and recognizable addition to the Knox Rapid Entry System.
The Knox 4500 is designed to be mounted on the outside of a building giving first responders the ability to control shunt trip devices from a safe distance. It is designed so that its contents are restricted only to first responders in possession of a Knox Master Key. It contains a switch mounted in a water-tight enclosure with clearly marked controls for safely de-energizing equipment or an entire facility in an emergency. Markings in large, bold type on a color-coded label clearly identify the two positions of the switch. The switch is able to be tagged with breakaway tamper seals to help indicate when the switch has been thrown or to tag the switch in the OFF position after it has been thrown. The Knox 4500 is offered in both surface-mount and recessed-mount configurations. Recessed configurations make the Knox 4500 even more secure against unauthorized entry. Tamper switches are provided as an option for monitored security on all configurations.
A special Alert Decal can be used when Knox 4500 Shutdown Station is on-site
It is important to note that the Knox 4500 is not intended to be accessed by building personnel or used as an emergency stop in the event of equipment failure. Its only purpose is to give first responders in possession of a Knox Master Key the opportunity to eliminate sources of electrical shock hazard and electrical combustion. The Knox 4500 is not designed to be connected to the primary power source of a building or piece of equipment but should only be connected to a remote shunt circuit.
In February 2011, a man was seriously injured while cleaning a wind turbine tower he thought had been de-energized. However the backup generator was still running, and while using a cleaning solution the man touched several wires electrocuting him and knocking him from his ladder. Applications in which backup power generation is used, either in the form of generators (fueled, wind, solar, etc), battery cells, or secondary grid sources, must have a power shut down protocol that renders both the primary and backup power sources de-energized for the protection of first responders. Depending on the complexity of the system being controlled multiple Knox 4500 Shutdown Stations may have to be employed.
For ease of access to remote shutdown stations in large facilities, multiple normally-open Knox 4500 stations can be wired in parallel to one or more paralleled shunt trip breakers so that any Knox 4500 in the system can trip all breakers. Power cannot be restored to equipment or to a building via the Knox 4500 switch. After returning the Knox 4500 to the ON position, power must be reset at the circuit breaker that was tripped by the remote trip device.
Because of the number of different applications and configurations in which the Knox 4500 could be used, Knox does not provide specific instructions for electrical installation. Knox does stipulate that the shutdown station must be installed by a qualified, licensed electrician following the guidelines of the shunt trip system to which it is being connected.