I-Line Application Data
The Four Types of Busway Runs
There are four major types of busway applications. Service Entrance Run, Plug-In Type Vertical Riser, Plug-In Type Horizontal Run and Feeder Type Tie Run illustrate the basic systems.
Service Entrance Run
Plug-In Type Vertical Riser
Plug-In Type Horizontal Run
Feeder Type Tie Run
Service Entrance Runs
Typical Connection of Transformer to Busway using Cables
For X dimensions, refer to NEC® Article 230–24.
I-Line II busway can be used as a service entrance conductor to bring power from a utility transformer into a distribution switchboard. Cable or solid bussing is used to connect to the transformer.
When the transformer is connected to the busway using cables, the governing electrical code can specify height clearance requirements for the cables.
The figure above illustrates the dimensions to consider when planning this type of run.
Service Heads
If the busway specifications or local utility require the service entrance cable-to-busway termination to be enclosed in a weatherproof box, then a service head should be ordered.
If the flatwise busway elevation is too low to allow a cable connection that would comply with the electrical code, the vertical service head (SV) could solve this issue. The SV is attached to busway that exits the rear of the switchboard and is turned upward (see Typical Vertical Service Head Application) or is attached to busway that exits the top of a switchboard and extends through the roof (see Vertical Service Head Penetrating a Roof).
If a vertical service head extends through a roof, the roof must be sealed around the busway. To do this, a fixed collar must be factory assembled onto the section of busway that penetrates the roof. The contractor can then install flashing from the collar to the roof. A roof flange kit can be ordered from the factory to make the flashing job easier. The kit consists of a drip flange and a roof collar. When installed, the roof collar must be sealed to ensure that no moisture gets indoors. The roof flange kit will accommodate a roof slope up to one inch per foot. See Detail A in Vertical Service Head Penetrating a Roof.
Transformer Taps
A transformer tap performs the same function as a service head, except that the lugs and bussing to which the service entrance cables are connected are not enclosed in a weather-proof enclosure.
A flatwise service head (SB) with the box removed is therefore a transformer tap (SF). An SF is a transformer tap for one three-phase transformer. Transformer Tap (One 3Ø Transformer) illustrates a typical SF service entrance run.
If three single-phase transformers are supplied by the utility to deliver power to the customer, a separate transformer tap has been designed for this application. This transformer tap is known as a “TTF” and is shown in Transformer Tap (Three 1Ø Transformers).
Bussed Transformer Connections
If required, the factory can provide a bussed transformer connection. This type of connection will include flexible connectors from the low voltage spades of the transformer to the busway connectors. These flexible connectors allow for busway expansion and contraction on the low voltage spades. Positioning of these flexible connectors is critical for proper alignment between the busway and transformer.
Bussed transformer connections are made for two types of transformers. One type has a low voltage throat as shown in Information Needed for Bussed Transformer Connection (Throat Type), and the other is a pad-mounted type with a low voltage compartment as shown in Information Needed for Bussed Transformer Connection (Pad-Mounted Type).
Phasing
With bussed transformer connections, it is necessary to properly coordinate the phasing of the transformer and of the switchboard it supplies. Schneider Electric can coordinate the phasing for you. Simply supply the name of the transformer manufacturer and phasing details of the low voltage side.
Other Service Entrance Connections
Occasionally, the customer or local utility will require a service entrance connection that differs from our standards. In this case, be sure to inform your Schneider Electric representative of any special dimensions, such as required height of service head from ground or floor, spacing between phase bars, number and type of lugs, distance from lugs to wall, phasing, etc.
Plug-In Busway Horizontal Run
Plug-in busway is used as a means of bringing power from a distribution switchboard to multiple loads throughout a building or manufacturing facility.
Phasing
A typical I-Line II plug-in run is shown in Measurements Needed for a Typical Plug-In Type Run. The phasing shown on the plug-in busway is “GABCN” top to bottom, with the top located as shown for a horizontal run. This phasing arrangement must always be followed to help ensure proper phasing of the plug-in units (see Detail A). Because this busway phasing must be followed, it is the busway that will determine the phasing of the switchboard.
Identification
When submitting busway run sketches for review, ensure that the plug-in busway sections are marked (P). See Measurements Needed for a Typical Plug-In Type Run.
Plug-In Risers
I-Line II plug-in busway can be utilized for the entire vertical riser. There is no need to use feeder busway to penetrate the floors. This feature enables the use of more plug-in openings per floor of the riser. (Plug-in risers under 800 A require internal barriers where the busway passes through a floor.)
Dimensions
The riser in Typical Information Needed for Riser has been fully dimensioned. Note that the feeder style busway has been used out of the switchboard and the two 120-inch (3048 mm) sections of plug-in style busway on the second and third floor do not have a joint located in or near the floor. Refer to Feeder Runs for a discussion and detail of joint accessibility requirements.
Typical Layout—800 A Rise shows typical dimensions that are known to ensure an accurate installation: floor-to-floor height, floor thickness, exact layout of multiple run riser, closet dimensions, the type and quantity of plug-in tap units per floor, which side of the busway the units should mount on, and (if necessary) the desired height of the units from the floor.
Riser Installation and Phasing
Circuit breaker types 250 A and below and the 30 A, 60 A, and 100 A fusible type plug-in units can be mounted on either side of the busway in riser installations.
When fusible type plug-in units are being supplied, the location of the plug-in unit determines the phasing of the busway. NEC Article 404.6 and CEC Article 14.502 state: “Single throw knife switches shall be mounted so that gravity will not tend to close them.” It is essential that the busway is oriented with the correct side available for the insertion of the units.
To determine the correct busway orientation (based on where the plug-in units mount for your installation), please contact your local representative for assistance and coordination.
Correct Orientation of Riser Busway shows the correct mounting and phasing of the riser busway and plug-in unit.
Special Manufacturer’s Recommendation
The NEC requires that a waterproof curb is installed at each floor opening where busway passes through (see Waterproof Curb Recommended at Floor Opening). An unprotected floor opening can act as a funnel for plumbing leaks, sprinkler system leaks, fluid spills, and other types of contamination.
The cost of removing and replacing a contaminated busway length far exceeds the cost for including a waterproof curb when the floors are poured.
Once busway is installed through a floor opening, the remaining unused area must be filled to prevent smoke from passing floor-to-floor (chimney effect) in case of fire in the building. Some recommended materials are fire-rated foam and caulk. Grouting is also acceptable, but it must be applied in a very dry form to prevent water and contaminants from entering the busway once the grouting cures and the water leeches out. Check with your local inspector to determine the appropriate materials to use in filling the void around the busway.
Plug-In Units
When entering an order, the factory must know not only which side of the busway the plugs will mount on, but also the type and quantity of plugs to use on each floor. Also, notify the factory if the plugs need to be mounted at a certain height from the floor.
Hangers
Spring hangers are recommended for riser applications. When properly installed and maintained, spring hangers compensate for expansion and contraction of the busway, as well as shrinkage of the building. In riser applications, support for busway must be provided at intervals not exceeding 16 ft (488 cm).
Feeder Runs
Feeder type runs are normally used for distributing power to loads that are concentrated in one area. Typical connections are switchboard-to-switchboard tie runs (see Measurements Needed for Feeder Type Run ), or a switchboard feeding a remote motor control center (MCC).
Busway Through Walls and Floors
When 800–5000 A busway extends through a wall or floor, feeder or plug-in busway can be used. For runs under 800 A, plug-in busway will be used throughout. In all cases, wall or floor location must be specified.
According to CEC Article 12.2000 and NEC Article 368.10, busway must be installed so that supports and joints are accessible for maintenance purposes after installation. This implies that no part of the tie channel can be inside the wall. Therefore, the distance from the center line of the joint to the wall must be greater than the distance from the center to the edge of the tie channel (see Joint Accessibility Requirements). If the dimensions of the tie channel cannot easily be determined, it is best to keep the joint at least 12 inches (305 mm) from the wall. This will ensure proper joint clearance for any type of busway passing through a wall or floor.
