What is SCCR and Why Does it Matter?

SCCR Explained: Why It Matters for Control Panels

When designing or specifying an industrial control panel, one term you’ll inevitably hear is SCCR, or Short Circuit Current Rating. For engineers, integrators, and safety-conscious designers, SCCR is crucial because it determines whether your panel (and all its components) can safely withstand a fault or surge without catastrophic failure.

GracePort is a family of panel interface connectors that let you access control signals, Ethernet, USB, and, optionally, power outlets from the outside of a control panel, keeping the panel door closed (for safety and NFPA 70E compliance). Because GracePort allows you to bring power out of the panel housing, questions inevitably arise: What is the SCCR of GracePort? Do the outlet options reduce panel SCCR? What must OEMs or users do so that the outlet doesn’t become the weak link?

What Is SCCR?

SCCR stands for Short Circuit Current Rating. It is the maximum fault current (in kiloamperes, kA) that a device or assembly, or a component within a system, can safely withstand under short-circuit conditions without damage beyond acceptable limits.

Put simply: if a short circuit happens, how much current can flow before things (contacts, insulation, mechanical mounts) start to fail? SCCR is the specification that answers that.

SCCR is often confused with interrupting rating (i.e., the amount of current a breaker or fuse can interrupt). But they’re not the same. A component with a high interrupting rating might be able to stop a fault current, but that doesn’t guarantee the rest of the system (wiring, connectors) can survive the transient stresses.

Why SCCR Matters

• Safety: A short circuit involves high currents, high thermal and mechanical stresses, and potentially arc faults. If your system isn’t rated for the available fault current, wiring or devices can melt, rupture, or explode.
• Compliance & Certification: In North America, UL 508A requires that industrial control panels (ICPs) be marked with SCCR and that the rating be justified.
• Weakest Link Approach: The SCCR of an assembly is limited by the lowest-rated component (unless mitigated via current limiting). You cannot exceed that lowest rating in your system design.
• Fault Current vs. Available Fault Current: Ensure that your SCCR is equal to or greater than the available fault current at the point of installation. If it isn’t, your panel is underspecified.

How SCCR Is Determined or Assigned

• Component Ratings: Each device (motor controller, contactor, fuse, busbar, and connector) must have an SCCR, typically obtained from testing or a datasheet. If unmarked, a default value is specified in UL 508A Table SB4.1.
• Modification via Current-Limiting Protection: If you place a current-limiting fuse or device upstream, you can raise the effective SCCR of downstream devices, since the fault current is curtailed. UL 508A SB4.3 outlines the procedure for adjusting SCCR using let-through current values.
• Weakest Link Rule: The overall panel SCCR is the lowest SCCR among all power circuit components after applying current-limiting protections.
• Nameplate & Documentation: The panel must be labeled with its SCCR, and internal design documents must support it.

To illustrate: if you have a power circuit with a motor starter rated at 5 kA, but you protect it with a Class J fuse combination-tested with that starter to 100 kA, then under those conditions the starter’s SCCR is effectively 100 kA. However, if you have a wire or connector rated only 10 kA downstream, that becomes your limit unless you also protect it.

How SCCR Applies to GracePort

GracePort connectors are designed to provide external access to control circuits, signals (such as Ethernet and USB), and optionally, accessory power outlets/receptacles, all while keeping the main panel door closed. This is critical for NFPA 70E “doors-closed” compliance and safer maintenance.

Because many GracePort configurations only carry control or signaling circuits (low voltage, low current), they do not pose a risk to SCCR; therefore, SCCR ratings are not required unless accessory power outlets are included. In other words:

• If your GracePort includes only control/signal components (such as USB, Ethernet, or switches), then SCCR does not apply to the GracePort itself for most use cases.
• SCCR only becomes relevant when a power outlet or receptacle is included inside the GracePort (i.e., you’re bringing line voltage through that interface).

So, when customers ask, “What is the SCCR rating of GracePort?” the correct response is: GracePort (by itself) is agnostic; SCCR comes into play only for the power outlet options included in the GracePort configuration.

SCCR of Accessory Power Outlets within GracePort

Because GracePort offers multiple outlet/receptacle choices, each has a different default SCCR (unless overridden via upstream protection). For context:

Since GracePorts are offered with a variety of power outlet options, the default SCCR ratings as defined in UL 508A Table SB4.1 apply to the power outlet offerings. OEMs (or panel designers) are required to use current-limiting Class CC fuses upstream to elevate the SCCR of those accessory outlets and align them with the panel’s required SCCR.

Below is a table summarizing the default SCCR values for various GracePort outlet types:

These default values come from the UL 508A framework and GracePort’s own product definitions. For example:

• A GracePort model P-A10B9R2 (which uses a domestic simplex outlet) is rated for 10 kA SCCR in its datasheet.
• Another model P-P33R2-F3R0 (also with simplex outlet) is likewise listed with 10 kA SCCR on its spec sheet.

Note: If a circuit breaker is included in the receptacle, its SCCR is only 0.2 kA, a very low value; therefore, this option is generally not suitable for use in higher-fault-current control panels without special upstream protection. Because outlets without circuit breakers often default to 10 kA, they are more robust in typical industrial control panel environments; however, they may still require current limiting if the available fault current exceeds 10 kA.

Why the Outlet Can Become the Weak Link (and How to Avoid It)

The panel’s SCCR is determined by the lowest SCCR component (post current-limiting adjustments). If you integrate a power outlet with only 2 kA or 0.2 kA SCCR into your panel, that outlet becomes your bottleneck, unless you limit the fault current it sees.

Including a low-SCCR outlet without mitigation is risky in environments where available fault current exceeds those values. To avoid degrading the panel’s SCCR, you must protect outlet circuits with current-limiting fuses of Class CC type (or similar, per UL 508A SB4.2/ SB4.3). These fuses limit fault current, allowing the outlet’s effective SCCR to be higher in a protected environment.

In practice: You place a Class CC current-limiting fuse upstream of the outlet circuit. That fuse will limit the peak and let-through current during a short, effectively insulating the low-SCCR component from the full force of the fault

The result: The outlet may behave (for safety purposes) like a higher-SCCR component under normal and fault conditions. This is the approach explicitly required in our Q&A: OEMs must use Class CC current-limiting fuses upstream to bring the SCCR of outlet circuits up to the same level as the panel.

Layout, Wiring & Coordination

• Use proper conductor sizing: fault forces scale with I2I^2I2. Thin wires can vaporize or be subjected to mechanical stress.
• Keep fault-current loops short by minimizing the distance between the fuse and the outlet to reduce extra stress.
• Avoid mixing high-SCCR and low-SCCR circuits without separation or proper protection.
• Document the protection scheme clearly. The UL certifier or inspector must verify that the low-SCCR component is adequately protected.

When GracePort’s SCCR Doesn’t Matter

If your GracePort configuration does not include power outlets, e.g., purely signal, USB, or Ethernet connections, then SCCR is not a design constraint for the GracePort itself. You don’t need to include it in the SCCR calculation of the panel (because no power circuit is involved).

For facility managers, the math is simple: fewer steps in compliance means fewer delays and less downtime. For technicians, it means safer, more comfortable work. Panel interface connectors bridge the gap between NFPA 70E compliance and everyday productivity.

If you’re ready to see how GracePort panel interface connectors can transform your maintenance practices, download our free GracePort eBook today and learn how to get started.

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