The present invention relates generally to enclosures for switchgear, panel boards, circuit breakers, and more particularly to a non-walk-in enclosure for low voltage switchgear and switchboard assemblies.
Switchgear and switchboard are general terms which cover metal enclosures, housing switching and interrupting devices such as fuses, circuit breakers, relays along with associated control, instrumentation and metering devices. The enclosures also typically include devices such as bus bars, inner connections and supporting structures used for the distribution of electrical power. Such metal enclosures can be maintained in a building such as a factory or commercial establishment, or they can be maintained outside of such facilities and exposed to environmental weather conditions. Typically, hinge doors or covers are provided on the front of the switchgear or switchboard sections for access to the devices contained therein.
Low voltage switchgear and switchboards operate at voltages up to 600 volts and continuous currents that can exceed 5000 amps. It is also possible that in short circuit conditions, intermittent currents exceeding 100,000 amps are possible.
When metal enclosures are used out of doors, switchgear and switchboard assemblies are typically housed in NEMA type 3R enclosures. Previous non-walk-in enclosures had the exterior doors closed over the circuit breaker doors and sealed against the indoor switchgear frame when the frame was wider than the circuit breaker doors. Other enclosures had the door sealed against a spacer that was used in the same plane as the front of the switchgear frame when the circuit breaker doors and the frame are nominally the same width. The spacer was needed to provide a sealing surface for the exterior door. Such prior art spacers are typically approximately two inches wide and are placed between each section of switchgear and switchboards. Such spacers add cost and proliferates parts to accommodate the added width of the enclosure. Conventional enclosure designs also lack space between the circuit breaker door and the exterior door of the enclosure thereby preventing a draw-out type circuit breaker from being placed in a disconnected position with the exterior door of the enclosure closed. In a situation where the enclosure is housed inside of a building, the additional width requirement takes up additional space.
Thus, there is a need for a non-walk-in enclosure for low voltage switchgear and switchboard assemblies that does not require the additional width of spacers between sections. There is a further need for an enclosure that will accommodate circuit breaker compartment doors that are nominally the same width as the sections in which the circuit breakers are housed. There is an additional need for an enclosure to allow the exterior doors to be closed when an enclosed circuit breaker is in a disconnected position.