B-Line Eaton heavy duty single-throw fused safety switch

The DH321NDK ships as a NEMA 12/3R enclosure in painted galvanized steel, so indoor dusty or dripping locations are covered as supplied. For outdoor rainproof duty you open the factory provided drain hole in the bottom of the enclosure, which is the field modification Eaton specifies to meet NEMA 3R. No other parts are needed to make that change.

Yes. It is a three-pole, four-wire fusible switch with a neutral, so a 120/240V single-phase or 240V three-phase feeder carrying a neutral lands properly. The neutral is bonded through a factory neutral assembly rather than switched, which is what you want for most motor and panel disconnect work. If your load has no neutral, the non-neutral version of the same 30A frame is the cleaner order.

The fuse clips are sized for Class H fuses up to 30A at 240V. Fuses are a separate order, so specify the class and amp rating for your load before install. If your design calls for Class R current-limiting fuses, you need a Class R rejection kit in this frame, since the base clips accept Class H.

Horsepower ratings on this switch are 1.5 hp single-phase and 3 hp three-phase with standard fuses, 3 hp single-phase and 7.5 hp three-phase with time delay fuses, and 5 hp at 250 Vdc. Time delay fuses are what let you get the larger motor out of a 30A frame, because they ride through starting inrush. Voltage rating is 240V, so this is not the switch for a 480V motor.

Lugs accept #14 through #2 AWG, and they are rated for both copper and aluminum conductors. That range covers a 30A branch circuit comfortably and leaves room for a long run upsized for voltage drop. Torque the aluminum terminations to the label values and use the appropriate antioxidant practice your spec calls for.

The enclosure measures 20 inches in length, 9.5 inches wide and 8.5 inches high, and the unit weighs 22 pounds. At that weight plan on fastening into studs or unistrut rather than drywall anchors, and allow working clearance in front per your local code before you pick the mounting spot.

A fusible switch like the DH321NDK gives you branch circuit overcurrent protection and a local disconnecting means in one box, which is what you want when the load is remote from the panel or the equipment nameplate calls for fuse protection sized below the upstream breaker. A non-fused disconnect only isolates, and is the right pick when protection is already provided upstream at the correct size, for example a rooftop unit fed from a dedicated breaker. Choosing fusible also means stocking the Class H fuses for service calls.

Order it as Eaton DH321NDK. For a multi-building standard that single number covers 30A, 240V, three-pole, four-wire with neutral, Class H fusible, in a NEMA 12/3R painted galvanized steel enclosure, so maintenance stocks one switch and one fuse class across the sites.

Heavy duty. That is the DH series construction, intended for industrial and commercial service where general duty switches are aimed at residential and light commercial loads. Practically, heavy duty means a more robust operating mechanism and interlocked cover for a 30A, 240V, three-pole application rather than the lighter general duty frame.