What are the Differences Between Metal Clad Switchgear and Metal Enclosed Switchgear?

Selecting the right medium-voltage switchgear is a foundational decision for any critical power system. It directly shapes system safety, long-term reliability, and how well the system runs day to day.

Engineers often face two primary options: metal clad switchgear and metal enclosed switchgear.

People frequently confuse these two types. While both use metal housings, their internal construction, safety features, and performance capabilities are fundamentally different.

The core distinction lies in compartmentalization and serviceability.

• Metal clad switchgear is built for maximum safety and uptime through strictly separated, grounded metal compartments and draw-out circuit breakers.
• Metal enclosed switchgear offers a more compact and cost-effective solution, with all components sharing a single enclosure.

Here is a brief overview of their key differences.

Defining the Categories

What Is Metal-Enclosed?

The term “metal-enclosed” technically describes any switchgear housed in a metal cabinet.

However, when making a direct comparison of metal clad vs metal enclosed switchgear, it specifically refers to a construction type with less strict design requirements than its metal clad counterpart.

This category is defined by a more integrated and compact design philosophy. It brings together multiple components into one shared space.

Its primary features include:

• Single Main Enclosure: All primary components, such as circuit breakers, busbars, and instrumentation, are located within one external metal housing.
• Limited Internal Barriers: While some barriers or partitions may exist, they are not the grounded, full-metal barriers required in metal clad designs. A fault in one area can more easily spread to nearby components.
• Typical Components: This equipment often uses fixed or non-draw-out circuit breakers, load-break switches, or switch-fuse combinations.
• Governing Standard: It is built to specific standards that ensure safe operation but do not require the strict compartmentalization of metal clad gear. These standards are set by organizations following NEMA (National Electrical Manufacturers Association) guidelines.

What Is Metal-Clad?

Metal clad switchgear is a specific, premium class of metal-enclosed switchgear.

It is built to meet a far more demanding set of construction and safety standards, making it the top choice for protecting the most critical electrical assets.

Its design philosophy puts safety, reliability, and ease of maintenance first above all else.

The defining features of metal clad equipment are:

• Strict Compartmentalization: This is its most important characteristic. The main circuit breaker, main bus, cable terminations, and low-voltage controls are each isolated in their own separate, grounded metal compartment.
• Draw-Out Circuit Breakers: Breakers sit on a racking mechanism, allowing workers to physically remove them from the enclosure. This makes safe, offline maintenance, testing, and fast replacement possible without shutting down the entire lineup.
• Automatic Safety Shutters: When a draw-out breaker is removed, grounded metal shutters automatically cover the stationary primary contacts. This keeps workers away from live parts.
• Mechanical and Electrical Interlocks: These safety systems stop unsafe actions, such as racking a closed breaker into the connected position or pulling out a breaker that is still carrying load.

A Head-to-Head Comparison

To make a well-informed specification, engineers must look at the direct differences between these two types of switchgear. The following table and detailed breakdown compare them across the most critical engineering and financial measures.

Construction and Compartments

The physical construction is the most visible difference between the two types.

• In metal clad switchgear, a fault such as a cable termination failure stays contained within its grounded metal compartment. This stops the fault from spreading to the main bus or nearby breaker compartments, protecting the rest of the system from a major failure.
• In contrast, the single-enclosure design of metal enclosed switchgear means an arc flash event in one area has a higher chance of damaging nearby components. This can lead to a longer and more widespread outage.

Governing Safety Standards

The standards shape the design.

• Metal clad switchgear follows IEEE C37.20.2 for Metal-Clad, a standard that clearly requires the features described above: grounded metal barriers, draw-out elements, and safety interlocks.
• Metal enclosed switchgear is often built to standards like IEEE C37.20.3 for Metal-Enclosed Interrupter Switchgear. While this standard keeps the equipment safe for its intended use, it does not require the same level of fault isolation or ease of service.

Maintenance and Downtime

This is where the operational difference becomes very clear.

• With metal clad gear, a technician can shut down a single feeder, rack out the breaker, and perform maintenance safely while the rest of the facility stays powered from the main bus.
• For many metal enclosed designs with fixed breakers, servicing a single device may require shutting down the entire switchgear lineup. In a data center or a continuous manufacturing plant, the cost of that downtime can quickly exceed the money saved on the cheaper equipment.

Arc Flash Mitigation

Personnel safety is the top priority.

The compartmentalized construction of metal clad gear gives workers much better protection during an arc flash event, since the grounded steel barriers help contain the blast and redirect pressure.

The ability to perform remote racking also allows operators to move the breaker from a safe distance, greatly reducing their exposure to arc flash energy.

Cost and Lifecycle Value

Metal enclosed switchgear consistently has a lower purchase price up front. This makes it an appealing option for budget-driven projects or less critical applications.

However, for mission-critical facilities, the analysis must go beyond the initial price tag to Total Cost of Ownership (TCO). The reduced downtime for maintenance, better safety, and greater system strength offered by metal clad switchgear often result in a lower TCO over the equipment’s 30-plus-year lifespan.

A Deep Dive into Standards

Simply citing standard numbers is not enough. Engineers must understand what these standards actually require, since this is what defines the equipment’s performance and safety. Let’s look under the hood.

IEEE C37.20.2 (Metal-Clad)

This standard is detailed and demanding. Key requirements include:

• Segregated Compartments: It clearly requires that the four main areas (breaker, bus, cable, low-voltage) be separated from each other by grounded metal barriers. There can be no intentional openings between them.
• Removable Elements: The standard sets the requirements for a draw-out mechanism, including distinct “connected,” “test,” and “disconnected” positions for the circuit breaker.
• Safety Interlocks: It requires interlocks that stop the breaker from moving when it is closed and prevent it from closing unless it is in the fully connected or test position.
• Insulation and Test Procedures: Metal clad gear must pass more demanding dielectric tests, including a higher Basic Impulse Level (BIL) rating, proving its ability to handle voltage surges from lightning or switching events.

Contrast with IEEE C37.20.3

In contrast, IEEE C37.20.3 for metal-enclosed interrupter switchgear is performance-based but less structurally demanding. It ensures the switch can safely interrupt load currents, but it does not require the strict compartmentalization, draw-out functionality, or extensive interlocking found in metal clad designs.

This produces a more compact and affordable piece of equipment that is perfectly safe and suitable for its intended applications. However, it lacks the ease of service and fault isolation of its metal clad counterpart. For definitive details, always refer to the official IEEE standards.

how to select a switchgear: metal enclosed vs metal clad

With this information in hand, how do engineers choose the right switchgear for a specific project? The process uses a decision framework based on application requirements, not just product labels.

Follow these steps to guide your specification:

1. Assess Criticality of the Load: Is the switchgear feeding a hospital’s operating rooms, a data center’s server racks, or a continuous process plant? If the cost of an hour of downtime is severe, the case for metal clad switchgear is strong. If it feeds non-urgent loads in a commercial building, metal enclosed switchgear may be enough.
2. Evaluate Maintenance Strategy and Downtime Costs: What is the facility’s plan for routine maintenance? If the strategy requires servicing individual feeders without shutting down the entire plant, draw-out breakers are a must. Calculate the financial impact of a full shutdown versus the added cost of serviceable gear.
3. Analyze Safety Requirements and Arc Flash Hazard Level: The available fault current at the switchgear’s location determines the potential arc flash energy. In high-energy environments, the superior containment and remote racking capabilities of metal clad switchgear become a critical safety requirement.
4. Consider Physical Footprint and Budget: Finally, balance the physical constraints and initial project budget. Metal clad switchgear needs more floor space and a higher upfront cost. If space is limited and the application is not mission-critical, the compact and affordable nature of metal enclosed switchgear is a valid solution.

Scenario 1: A Regional Data Center

Here, the primary driver is 100% uptime. The financial penalty for a single outage is enormous. The maintenance strategy involves regular, proactive servicing of breakers.

For this application, metal clad switchgear is the only responsible choice. Its fault containment stops a single feeder issue from taking down the entire facility, and its draw-out breakers allow for maintenance with zero disruption to the critical load. The higher initial cost is easily justified as protection against costly downtime.

Scenario 2: A Commercial Real Estate Development

This project involves a multi-tenant office building. While power reliability matters, the loads are not as critical as those in a data center.

The electrical rooms are small, and the initial construction budget is a key constraint. Here, metal enclosed switchgear is an excellent fit. It delivers safe and reliable power distribution in a compact footprint and at a lower upfront cost, and scheduled maintenance can be planned for off-hours or weekends to minimize disruption to tenants.

A Decision of Value

The choice between metal clad vs metal enclosed switchgear is a classic engineering trade-off. It is not about which is “better” in isolation, but which is the right fit for the application.

Metal clad switchgear puts maximum safety, serviceability, and system strength first for the most demanding and critical power systems. Metal enclosed switchgear provides a safe, reliable, and cost-effective solution for less critical applications where footprint and initial budget are the main concerns.

Ultimately, the decision should never rest on initial cost alone. It must be a full assessment of the application’s long-term needs for safety, reliability, and operational continuity.