Segment Fill Validation - Intergraph Smart Electrical - Help - Hexagon

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You can perform segment fill validation using one of the two methods, the Conventional or the National Electric Code (NEC) method. Note that the software can calculate the fill percentage only if the segment is associated with a reference raceway component.

Conventional Method

The Conventional method is based on the physical properties of raceway components. This method is commonly used and it has a less restrictive approach than the NEC method. For details on how to set the required method (Conventional or NEC), see Set the Method for Segment Fill Validation.

Tray Fill Calculation

The software calculates tray segment fill according to the following criteria:

  • When using the Conventional method, the segment fill calculation is based on the type of reference tray that you select on the Reference Cableway Component Common Properties dialog. The following types of reference trays are available:

  • Covered tray segment - Applies to trays and miscellaneous cableway components. The software calculates the total area occupied by the cables assigned to the segment. The software validates this value by ensuring that it does not exceed the allowed area (the product of tray width, tray depth and Fill factor), Smart Electrical validates the covered tray fill segment calculation by area. Furthermore, the software ensures that the outer cable diameter of any cable does not exceed the tray depth. Note that for covered trays the fill factor value cannot exceed the value of 1.

  • Uncovered tray segment - Applies to trays and miscellaneous cableway components. The software calculates the sum of the outer diameters of the cables assigned to the segment. Smart Electrical validates this value by ensuring that it does not exceed the product of the segment width, the fill factor, and the number of layers. The software validates the uncovered tray fill segment calculation by diameter.

  • The segment fill calculation is based on tray width or tray area. You select the required criterion from the Calculation criteria list on the Cableway Segment Common Properties dialog. When selecting the Auto option from the Calculation criteria list, Smart Electrical calculates the segment fill automatically. The software performs the calculation according to the type of reference tray that you selected on the Reference Cableway Component Common Properties dialog. Selecting the Covered check box instructs the software to calculate the segment fill according to the Area criterion. If you do not select this check box, Smart Electrical performs the calculation according to Width.

  • The Fill calculation takes into account the NEC validation rules, but for information purposes, what is actually displayed is the total fill percent value of all of the cables on the tray.
    For Example when large and small cables are located on the same tray , according to NEC rules, there should be a validation that the small cables area does not exceed the maximum allowed area.
    This validation is calculated within the application but not presented on screen.

    • For an engineering process that requires replacement of multi-core cables with parallel sets of single-core cables, it is recommended to dissociate the multi-core cables from all the cable routing segments before the replacement with single-core cables, and then perform new routing after the replacement.

    • For details on how to set the segment fill calculation criterion, see Set the Segment Fill Calculation Criterion.

Conduit Fill Calculation

The Conduit fill calculation applies to conduits. The software calculates the total area occupied by the cables assigned to the segment. Smart Electrical validates this value by ensuring that it does not exceed a quarter of the allowed area of the conduits. The software calculates the allowed area of the conduit starting from the conduit diameter and the fill factor. The minimum allowed conduit diameter is based on the following formula:

D= 2*F*SQRT(SIGMA d**2)

Where:

  • D = Minimum inner conduit diameter

  • di = Individual cable outer diameter

  • f = Fill factor (between 0 and 1)

  • For conduits, the fill factor value cannot exceed the value of 1.

  • You need to define cable diameter and weight per unit length for each associated reference cable by entering the required values in the Reference Cableway Component Common Properties dialog.

  • When performing validations based on cable diameter, the software assumes that the cables are laid side-by-side. Therefore the software does not allow for cables that can pass along the interstices between larger cables.

NEC Validation Method

Smart Electrical validates segment fill based on the NEC 2011 Handbook. The NEC method is based on given space factors in lookup tables. Unlike the Conventional tray segment validations, the NEC method does not allow flexibility like the Conventional method regarding tray segment fill validation. NEC dictates the fill requirements for various cases of installations, such as cable formations, cable sizes, insulation voltages and tray widths. Smart Electrical supports routing of single-core and multi-core cables through the same segment as allowed in NEC 2011 Handbook. The software takes into account the fill factor that you specify and the maximum weight per length unit allowed on tray. If any of the actual fill values exceed the allowed values, the software rejects them from being routed and displays a warning message on the Cableway Segment Common Properties box.

The Flexible tray type check box is not available when NEC validation is set to Yes.

Conduit Fill Factor

When using the NEC validation method in a conduit, the software sets the fill factor according to the number of cables in the conduit:

  • If the number of cables in a conduit = 1, the fill factor = 0.53

  • If the number of cables in a conduit = 2, the fill factor = 0.31

  • If the number of cables in a conduit > 2, the fill factor = 0.4

You cannot modify these additional fill factors.

The NEC rules for tray segment fill validation are based on the following primary parameters and their various combinations:

  • The insulation voltage rating of the cable that it is carrying. The NEC method divides the voltage into two groups, above 2000v and 2000v, and below.

  • A combination of power and non-power carrying cables (instrumentation, control, grounding).

  • Type of tray on which cables are laid; whether it is Ladder, Ventilated trough, Solid bottom tray, Ventilated channel, Solid channel.

  • Conductor sizes

  • Tray dimensions

For each of the possible combinations of the above-mentioned parameters, NEC method specifies (NEC 2011 handbook) one or more of the following criteria:

  • The allowable number of layers

  • The allowable fill area

  • The allowable tray width percentage

All the limiting numbers of the allowable width and cross-sectional areas are automatically set in Smart Electrical and cannot be changed.

Smart Electrical generates a NEC tray fill validation log file that documents tray validations. For details on how to generate a log file, see Generate Error Log Files. In the generated log file you can view the properties of the specific tray fill validation, such as - Item type, date of validation, Layout ID, and more. The NEC tray fill validation log file is based on Smart Electrical Tray Fill Calculation Logic, which is based on: NFPA 70 National Electrical Code 2011 Edition.

For more details see, NEC tables, refer to article 392, section 9 and 10 in the NEC 2011 Edition.