New Wiring Types in Revit MEP 2019: What You Need to Know

Revit MEP 2019 New Feature: Wiring Types

The Wiring Type table allows you to define and manage the types of wires used throughout your project. You can add or remove wire types as needed, and multiple wire types can be specified for a single project. The first wire type listed in the table becomes the default for all circuits created, representing the most commonly used wire in your design.

Wire types can be managed online via the Attributes palette, where you can select a different wire type for any given circuit. The table includes the following fields:

• Name – A user-defined string that identifies the specific wire type.
• Material – The wire’s conductor material, such as Copper or Aluminum. You can also define new project-specific materials through the dialog box.
• Rated Temperature – Options include 30°C, 60°C, or 95°C, or you can specify a custom temperature rating for your project.
• Insulation Layer – Depending on the conductor material, you can select from multiple insulation types or define a new project-specific insulation layer.
• Maximum Size – Defines the largest wire size available for this wire type, ranging from 14 MCM to 2000 MCM. This parameter controls when wire resizing occurs in parallel circuits, preventing the size from increasing unchecked up to 2000 MCM.
• Neutral Load Multiplier – This value adjusts the neutral wire size by increasing or decreasing it based on a multiplier. Similar to upsizing a ground wire during voltage drop scenarios, this allows the neutral wire to be sized larger than the calculated minimum to accommodate specific conditions.

When applying the neutral load multiplier, the adjustment is based on the cross-sectional area of the wire rather than its current-carrying capacity. This is especially important for handling increased currents caused by harmonic loads, which are common in many electrical devices with switching power supplies. Such loads produce harmonic distortion in the current waveform, resulting in higher actual current flow than expected.

After calculating the neutral load size—adjusted according to the live conductor or unbalanced current—you apply the neutral load multiplier to finalize sizing.

• Required Neutral Load – If selected, all circuits using this wire type will include a neutral wire, even for balanced three-phase loads that might not typically require one. If not selected, balanced neutral loads will be excluded, but unbalanced loads will still include a neutral wire.
• Neutral Load Size – Specifies the basis for adjusting the neutral wire size. Options include:
  Wire size – Neutral wire sized the same as the live wire.
  Unbalanced current – Neutral wire sized according to the actual unbalanced current.
• Tube Type – The conduit material affects wire impedance, which influences voltage drop calculations. Click the value to select from options such as Steel or Non-magnetic.

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