Why does switchgear come with so many “metal-something” labels?
A specifier comparing bids for the same feeder will often see three construction classes quoted at three different prices — and the single-line diagram looks identical on all three. The labels metal-clad, metal-enclosed, and switchboard are not marketing terms. Each maps to a distinct North American standard, a distinct level of internal compartmentalization, and a distinct expectation about fault duty, maintenance, and service life. Choosing the wrong class either overpays for a duty the site will never see or, worse, under-builds protection on a bus that needs it. The distinction matters most in substation and power-distribution line-ups feeding critical load.
How do metal-clad and metal-enclosed switchgear differ?
The cleanest way to read a medium-voltage quote is by the governing standard.
Metal-clad switchgear
Metal-clad switchgear is governed by IEEE C37.20.2, the Standard for Metal-Clad and Station-Type Cubicle Switchgear. Its defining feature is compartmentalization. Major parts of the primary circuit — the interrupting device, the main bus, the instrument transformers — are each enclosed by grounded metal barriers, and the main interrupting device is a removable drawout circuit breaker that self-aligns and self-couples as it racks between the connected and disconnected positions. IEEE C37.20.2 covers ratings from 5 kV through 38 kV, with main-bus continuous-current ratings of 1200 A, 2000 A, and 3000 A. The grounded barriers make an internal fault more likely to stay in one cubicle, and the drawout design lets a breaker be withdrawn and serviced without working on an energized bus. Metal-clad switchgear is the default where fault duty is high or the protection scheme is sophisticated.
Metal-enclosed interrupter switchgear
Metal-enclosed interrupter switchgear is governed by IEEE C37.20.3, whose 2023 edition is titled the Standard for Metal-Enclosed Interrupter Switchgear Rated above 1 kV AC up to and Including 48.3 kV AC. It typically combines interrupter switches and power fuses rather than drawout breakers, and it does not require the full grounded-barrier compartmentalization of a metal-clad design. That makes metal-enclosed switchgear lighter, more compact, and lower in cost — a sound fit for feeders that switch infrequently and sit below the fault levels that justify drawout breakers. Where space or environmental sealing drives the design, gas-insulated switchgear compresses the same function into a far smaller footprint.
Is low-voltage switchgear the same as a switchboard?
No — and the confusion is common because both sit at 1000 V or less. Two different UL standards apply.
Low-voltage switchgear is built to UL 1558, the Standard for Metal-Enclosed Low-Voltage Power Circuit Breaker Switchgear, covering equipment rated 1000 V ac nominal (1058 V ac maximum). It uses drawout power circuit breakers tested to UL 1066, which can be racked out and serviced while the structure stays in place. A switchboard is built to UL 891, which applies to switchboards rated 1000 V or less, and normally uses fixed-mounted molded-case circuit breakers tested to UL 489 — a standard that covers devices rated 6000 A or less.
The practical split is one of role. Low-voltage switchgear is primary distribution, often bolted to the secondary of a service transformer, where high short-circuit withstand and drawout serviceability earn their cost. A low-voltage switchboard is secondary distribution — feeding panelboards and loads downstream — where compactness and installed cost matter more than racking out a breaker live.
What about arc-resistant construction?
Any of these classes can be specified as arc-resistant, tested to IEEE C37.20.7 for switchgear rated up to 52 kV. The test verifies that an internal arcing fault is contained and its energy redirected away from personnel rather than blowing out the front of the enclosure. Accessibility ratings describe where that protection applies — Type 1 at the front only, Type 2 at the front, sides, and rear. Arc-resistant construction is increasingly specified for data center and industrial EPC line-ups where personnel work close to energized equipment.
Where does each class make sense?
| Class | Standard | Interrupting device | Best fit |
|---|---|---|---|
| Metal-clad | IEEE C37.20.2 | Drawout breaker | High fault duty, frequent switching, critical feeders |
| Metal-enclosed interrupter | IEEE C37.20.3 | Switch and power fuse | Lower-duty MV feeders, infrequent switching |
| Low-voltage switchgear | UL 1558 | Drawout breaker (UL 1066) | Primary LV distribution, high withstand |
| Switchboard | UL 891 | Fixed molded-case breaker (UL 489) | Secondary distribution to loads |
What should a buyer specify?
Anchor the specification to the standard, not the label. State the rated maximum voltage and the short-circuit and short-time withstand the bus must survive, because that pair usually decides metal-clad versus metal-enclosed. Call out whether breakers must be drawout for live serviceability. Specify the accessibility type if arc-resistant construction is required, and confirm it against the locations where staff will actually work. Finally, confirm coordination with upstream and downstream protection so the chosen class supports the relay scheme the site needs.
How this maps to Entogo’s lines
Entogo builds the full range in its own Toronto factory — metal-clad and metal-enclosed switchgear, gas-insulated switchgear, and low-voltage switchgear and switchboards — each designed and built to the governing IEEE and UL standards above; UL (cULus)/CSA certifiable on request. Because the line-ups are engineered and manufactured in-house, construction class, ratings, and arc-resistant options can be matched to the application and to the substation and power-distribution scheme rather than to whatever a distributor happens to hold in stock. For sizing or a class recommendation against a specific single-line, contact the engineering team.
