"Metal-clad" and "metal-enclosed" get used almost interchangeably in conversation — but the standards define them very differently, and the difference shows up directly in spec compliance and lead time.
Both terms describe medium-voltage switchgear enclosed in grounded metal, but the similarity mostly ends there. Metal-clad switchgear, defined by IEEE C37.20.2, requires: draw-out circuit breakers that can be racked in and out without opening the compartment, grounded metal barriers separating the major compartments from each other, and automatic shutters that close over the primary disconnects the moment a breaker is withdrawn. Metal-enclosed switchgear, defined by IEEE C37.20.1, doesn't require any of that — breakers or fused switches can be fixed-mounted, and the internal barriers are less strict. Metal-clad is the higher-integrity category, and it's built and priced accordingly.
A typical metal-clad vertical section is divided into four separated compartments, each isolated from the others by grounded metal barriers:
| Compartment | Contains |
|---|---|
| Circuit breaker | The draw-out breaker cell itself — connect, test, and disconnect positions, with interlocks preventing racking under load. |
| Bus | The main horizontal and vertical bus bars distributing power between sections — fully insulated and barriered per C37.20.2. |
| Cable / termination | Incoming and outgoing cable terminations, and often the current and potential transformers used for metering and protection. |
| Low-voltage (control) | Protective relays, meters, control switches, and the secondary wiring that ties the breaker's trip/close circuits to protection. |
The compartment separation is the actual safety mechanism: a technician can open the low-voltage compartment to work on protection relays while the bus and cable compartments stay fully enclosed and energized, without needing to de-energize the whole section.
Below about 1000V, the relevant standards shift again — low-voltage metal-enclosed switchgear falls under IEEE C37.20.1 as well, but is more commonly specified and tested to UL 1558 in North America. Draw-out breakers are common but not universal at this voltage class, and the compartmentalization requirements are lighter than medium-voltage metal-clad gear.
Arc-resistant switchgear (tested per IEEE C37.20.7) is an additional certification layered on top of the metal-clad or metal-enclosed base design — it verifies the enclosure can vent and contain an internal arc fault without the doors or panels becoming projectiles, protecting personnel standing at the front, sides, or rear (Type 1, 2, or 2B accessibility, depending on which sides are rated). It's a separate spec line from "metal-clad" and should be called out explicitly if required — see the related concepts in the arc-flash boundary basics guide.
Metal-clad construction requires more manufacturing steps than metal-enclosed — draw-out mechanisms, interlocking shutters, barriered compartments built and tested to a stricter standard — so it typically carries a longer lead time at the same voltage and current rating. Current MV switchgear lead time is tracked on the Lead-Time Index; as of this writing it's effectively sold out through 2028 across the market, which makes getting the compartment-type spec right on the first RFQ more important than usual — a respec after the order is placed can mean starting the queue over.
The Data Centers and Industrial Supply desks carry MV switchgear configured by compartment type, voltage class, and interrupting rating, with current lead time shown before you commit to a spec. Unfamiliar with a term above? Check the glossary, or run available fault current — the number that ultimately sets breaker interrupting rating — through the fault current calculator.
Metal-clad switchgear (IEEE C37.20.2) requires draw-out circuit breakers, grounded metal barriers separating the main compartments, and automatic shutters that cover primary disconnects when a breaker is withdrawn. Metal-enclosed switchgear (IEEE C37.20.1) doesn't require those features — breakers or fused switches may be fixed-mounted rather than draw-out, and the internal compartmentalization is less strict. Metal-clad is the higher-integrity, and typically higher-cost and longer-lead-time, category.
A typical metal-clad lineup has four separated compartments per section: the circuit breaker compartment (the draw-out breaker cell), the bus compartment (main bus bars, barriered), the cable/termination compartment (incoming/outgoing cable connections and instrument transformers), and the low-voltage compartment (protective relays, meters, and control wiring).
Metal-clad switchgear requires more manufacturing steps — draw-out mechanisms, interlocking shutters, barriered compartments — and is built to firmer utility and industrial specs, so it generally carries longer lead times than metal-enclosed equipment at the same voltage class. Current market lead time for MV switchgear is tracked on the Voltfield Lead-Time Index.
Configure by compartment type, voltage class, and interrupting rating, and get a quote with real lead time in 24 hours.