194R-HM4E — 194R Fusible Disconnect Switch, 40A, 600V AC, 3-Pole

The 194R-HM4E is a 40A three-pole fusible disconnect switch from the 194R series, rated for 600V AC. It mounts on a 35 mm DIN rail and provides manual disconnection, motor branch circuit protection (via fuses), and lockout capability in a single compact unit. The combination of isolation and protection in one device reduces panel wiring complexity and saves the space that a separate molded case circuit breaker or fused disconnect would occupy.

In motor branch circuits, the 194R series satisfies two separate electrical code requirements simultaneously: the disconnecting means (allowing safe isolation of a motor for maintenance) and the short-circuit and ground-fault protection (provided by the fuses). For facility electricians working to NEC or IEC standards, having both in one listed device streamlines the panel layout and the inspection process.

Specifications

Parameter	Value
Part Number	194R-HM4E
Series	194R
Poles	3
Rated Current	40 A
Rated Voltage (AC)	600V AC
Rated Voltage (DC)	250V DC
Fuse Type	Class J (IEC) or Class CC / J (UL)
Fuse Size	Up to 40A (per pole)
Short-Circuit Rating	100 kA (with Class J fuses)
Utilization Category	AC-23A (motor branch circuit)
Mounting	35 mm DIN rail
Enclosure	IP20 (open; panel or enclosure mounting)
Padlockable	Yes (handle lockable in OFF position)
Operating Temperature	−25°C to 55°C
Standards	UL 98B, IEC 60947-3, CE

Current Rating and Fuse Selection

The 40A body rating represents the maximum continuous current the switch handles. The fuses inserted into the switch provide the actual short-circuit protection and determine the overload response curve. Selecting the correct fuse size for the motor requires:

Motor FLA (full load amps): from the motor nameplate. This is the baseline for fuse sizing.
NEC or IEC code fuse sizing rules: NEC 430.52 permits motor branch circuit fuses to be sized at up to 175–300% of motor FLA depending on fuse type (to accommodate motor inrush without nuisance blowing). IEC uses similar overload multipliers. The specific percentage depends on the fuse class and whether the motor has high starting current requirements.
Fuse class matching: the 194R-HM4E uses Class J fuses. Verify the fuse class is as specified — inserting a different fuse class may not fit physically and could compromise the switch's 100 kA short-circuit rating.

Installation Notes

Mount on a 35 mm DIN rail with adequate space above and below for conductor routing. Line-side terminals are at the top; load-side at the bottom in standard orientation.
Tighten terminal screws to the specified torque (typically 2.0–2.5 Nm for 40A terminals). Under-torqued connections at 40A cause resistive heating that can damage insulation and the terminal block over time.
The switch must be installed inside an appropriate enclosure to meet NEC or IEC installation requirements — the IP20 rating is not sufficient for protection against contact hazards or environmental exposure on its own.
Lockout padlocking: the handle accepts a lock through its locking aperture in the OFF position. Verify the padlock shackle diameter is compatible with the aperture — standard safety lockout padlocks (6 mm shackle) are typically appropriate.
Fuse replacement: replace all three fuses simultaneously when any one fuse blows. Single-phasing a three-phase motor (running with one blown fuse) causes severe motor damage within seconds to minutes.

FAQ

Q: Can this switch be used as the sole branch circuit protection device, or does it need a separate breaker upstream?

With Class J fuses installed, the 194R-HM4E meets the requirements for a motor branch circuit disconnect and short-circuit protection device in one unit. A separate upstream breaker is typically required only for the feeder protection, not as a redundant branch circuit device. Verify with the applicable electrical code and AHJ for the specific installation.

Q: What fuse size is typically used with a 15 HP, 480V three-phase motor?

A 15 HP, 480V motor has a nameplate FLA of approximately 21A. Under NEC 430.52 with Class J fuses, the maximum permitted fuse size is 175% of FLA = approximately 36A. A standard 35A or 40A Class J fuse is commonly used. Verify with the actual motor nameplate and local code requirements — specific conditions may permit or require different sizing.

Q: Can DC loads be switched with this disconnect?

The 194R-HM4E has a 250V DC rating per pole. For three-phase AC motors at 480V or 600V AC, the AC rating applies. DC applications at up to 250V DC per pole are permissible. Multi-pole series connections for higher DC voltages require specific configuration — consult the product documentation.

Q: Is an auxiliary contact available for remote status indication?

Yes. The 194R series supports auxiliary contact add-on blocks that mount directly to the switch body, providing NO/NC contact outputs for remote status indication or interlocking with the control system. The specific auxiliary contact catalog number should be verified against the 194R accessory selection guide.

194R-HM4E Genuine Disconnect Switch 194RHM4E