Electrical Wiring Methods: Splitters, Cable Trays, Gutters, and Wireways

Wiring Devices and Connectors

• Connector Body: Defined as a female cord-mounted wiring device. It features conducting elements that are recessed behind a mating surface.
• Flange Inlet: A device that is flange-mounted rather than cord-mounted, distinguishing it from a standard plug.
• Standards:
  • Some pin acetyl devices are built to European standards.
  • European endlessly connectors utilize color-coding to indicate voltage ratings.
  • Safety features: To prevent plugging a device into the wrong receptacle (e.g., a yellow plug into a red receptacle), ground pins are located in different positions depending on the voltage rating, making a mismatch impossible.
• Pin Identification and Security:
  • Common ratings discussed include $250\,V$ and $20\,A$.
  • A way-to-plug receptacle is used as long as the voltage does not exceed $250\,V$.
  • The ground pin is identified by its L-shape, while the center pin is round.
  • Twist Lock: The primary advantage of a twist-lock connector is that it is the most likely device to stay secured and not fall out of the receptacle.

Motor Control Center (MCC) Safety and Alternatives

• Alternative Wiring Methods: The curriculum focuses on four specific items used as alternatives or supplements to Motor Control Centers (MCC):
  • Splitter troughs.
  • Cable trays.
  • Auxiliary gutters.
  • Wireways.
• MCC Considerations: While MCC centers are "all-in-one" and often easier to manage, they can be expensive. Installations with numerous separate disconnects can appear messy compared to a unified MCC.
• Physical Protection:
  • Equipment is often fitted with yellow guarding because of past incidents where machinery or vehicles struck the components.
  • Warning: Impacting a $600\,V$ electrical component with a fork truck is extremely dangerous to the operator.

Splitter Troughs

• Definition: An enclosure containing terminal plates or bus bars with main and branch disconnections. Used with auxiliary gutters, they perform tasks similar to an MCC power bar.
• Application: Used at points where a large conductor supplies power to several smaller conductors.
• Requirements:
  • A splitter box is mandatory if the large conductor is size number $6$ copper or larger.
  • Conductors smaller than number $6$ copper may be spliced in a standard junction box without a splitter.
  • Note: When conductor size is reduced, additional overcurrent protection is usually required for the smaller conductors due to lower ampacity (Refer to Rule $14,100$ for general guidelines).
• Installation Rules:
  • The rules for splitter boxes are mixed with rules for busways in the electrical code.
  • Each conductor entering the box must have a separate terminal screw.
  • Prohibition: Splitters cannot be used as a raceway to permit conductors to pass through without being connected to the terminal pads.
  • Mounting: Typically surface-mounted, but can be installed in a wall if the door remains accessible. They can be mounted horizontally (most common) or vertically.
  • Accessibility: Must be mounted in an accessible location where the cover can be opened without dismantling other equipment.

Cable Trays

• Definition: A raceway consisting of troughing and fittings constructed so that insulated conductors and cables can be readily installed or removed after the tray system is completely installed.
• Styles: Ladder style, ventilated, and non-ventilated.
• Installation Guidelines:
  • Must be supported at intervals specified by the manufacturer using non-combustible materials (e.g., threaded rods, nut/bolt setups).
  • Fire Safety: Cable trays must not pass through a wall made of combustible material (e.g., a wooden wall); they may pass through concrete walls.
  • Clearances are governed by section $12-2200$ of the electrical code.
• Conductor Rules:
  • Reference: Section $12-2202$.
  • Cables used must be those listed in Table $19$ of the electrical code.
  • Single conductor cables must be secured to the tray using non-ferrous clamps to prevent heating caused by magnetic forces.
  • Splices are permitted in the cable tray if the joint is accessible and the connectors are properly insulated.
• Grounding and Ampacity:
  • Metallic cable trays must be grounded in at least one spot. Bolts holding the sections together are considered sufficient to provide grounding continuity between sections.
  • Ampacity: Determined by the spacing of the cables. Cables spaced correctly can run at full capacity (Tables $1$ through $4$). Cables installed close together must have their ampacity de-rated based on Tables $5A$ through $5D$.
• Maintenance: Cable trays can accumulate dust, which presents a significant fire hazard, especially during activities like welding.

Auxiliary Gutters

• Definition: A sheet metal enclosure used to supplement the wiring space of equipment and the interconnecting conductors.
• Distinction from Splitter Troughs: While they look similar externally, auxiliary gutters contain no busbars or terminal points; they are used strictly for the travel of insulated conductors.
• Limitations:
  • Cannot contain devices such as relays, control transformers, or busbars.
  • Maximum length: $6\,m$ beyond the edge of the equipment it supplements.
  • Not to be used as a general raceway; it is specifically for sorting and grouping conductors.
• Electrical Code Specifications:
  • Classified as a raceway; therefore, the maximum number of conductors is $200$.
  • Must be securely supported and fastened at intervals not exceeding $1.5\,m$.
  • Fill Capacity: The cross-sectional area of the conductors cannot exceed $20\%$ of the cross-sectional area of the gutter.
  • Separation: In MCC-like applications containing both load and control conductors, a horizontal sheet metal divider is required to separate power and control wiring for safety.

Wireways

• Definition: A raceway consisting of a completely enclosed trough for conductors.
• Environmental and Installation Constraints:
  • Used only for exposed work; cannot be installed inside a wall.
  • Generally intended for indoor, dry locations.
  • Ends of the wireway must be closed with an approved fitting.
• Structural Rules:
  • If passing through a wall or floor, the point where two sections join (the seam) must not be located inside the wall or floor.
  • If installed less than $2\,m$ from the floor, physical protection against mechanical damage must be provided.
• Fill Capacity:
  • General use: Maximum fill is $20\%$ of the cross-sectional area.
  • If the wireway contains only control wires, the maximum fill rate increases to $40\%$.

Summary of Wiring Systems

• Splitter Trough: Primarily used where a large conductor distributes power to smaller conductors.
• Wireway: A sheet metal trough used for routing conductors from point A to point B.
• Auxiliary Gutter: A box used to simplify conductor routing from multiple locations to a panel board.
• Cable Tray: An exposed metal tray or ladder system used for running cables throughout a building.

Questions & Discussion

• Question (Audience): Regarding literacy and testing, did the students have to do testing before coming here?
• Response (Instructor): No, but the instructor mentions a nephew attending Mohawk College who had to do an interview and literacy/math testing before entry, suggesting it may be a regional requirement or specific to certain programs to ensure students are prepared.
• Question (Audience): Regarding wireway fill calculations—if the math results in a fraction (e.g., $355.9$ wires), do you round up to $356$ or keep it at $355$?
• Response (Instructor): You would likely round up, but the instructor notes that it doesn't make a drastic difference, especially since the code specifies a maximum of $200$ conductors in some contexts.