Original Ohmite Model N Rheostat 15 Ohm 4.47A 300W

If your project or repair demands high-current handling without compromising thermal stability, the Ohmite Model N 15 Ohm Rheostat is the professional choice. Manufactured in the USA, this passive electromechanical component is engineered to withstand demanding industrial environments while delivering reliable and precise resistance adjustment.

Design and Construction
The Ohmite Model N features a vitreous enamel-coated ceramic core, a hallmark of industrial-grade wirewound rheostats. This construction not only secures the wirewound resistive element in place, preventing shorts caused by vibration, but also provides excellent heat dissipation for continuous high-power operation. The heavy-duty metal wiper arm ensures smooth, continuous travel along the resistive element, delivering precise resistance adjustment while minimizing electrical noise and contact wear.

Applications and Uses (What Is It Used For?)
This component is intended for maintenance engineers, vintage equipment restoration technicians, university laboratories, and machine builders. Its primary applications include:

• DC Motor Speed Control: Provides precise speed adjustment for DC motors used in industrial machinery.

• Load Banks: Used for testing generators, power supplies, and other electrical power equipment under controlled load conditions.

• Generator Field Control: Used to adjust the generator field current and regulate the output voltage.

• Equipment Restoration: Direct replacement for vintage radio transmitters, welding equipment, and antique industrial control panels.

• Electronics Laboratories: Ideal for experimenting with high-power voltage divider circuits, variable loads, and power dissipation testing.

Product Condition Notice:
This is a used item acquired from a surplus lot of electronic equipment. It does not include the original packaging. The rheostat has been tested for continuity and smooth resistance variation using a high-precision digital multimeter, confirming proper mechanical and electrical operation. It shows cosmetic wear consistent with industrial use, which does not affect its performance or functionality.

Manufacturer Heritage (Ohmite Manufacturing Co.)
Founded in 1925 in Chicago (later relocated to Skokie, Illinois, as indicated on the nameplate), Ohmite Manufacturing Company is one of the most respected names in power electronics. The company pioneered vitreous enamel resistor technology, setting the industry standard for high-power wirewound resistors and rheostats. Ohmite components played a vital role throughout the industrial expansion of the 20th century, including applications in military, aerospace, telecommunications, and heavy industrial equipment. Owning an Ohmite component means owning a genuine piece of American electrical engineering history.

Technical Specifications (Datasheet Format)

• Manufacturer: Ohmite Mfg. Co. (Skokie, IL, USA)

• Model: N

• Component Type: Power Rheostat / Wirewound Variable Resistor

• ΩNominal Resistance: 15 Ω

• Maximum Current Rating: 4.47 A

• ≈P=I2×RPower Dissipation (Calculated): 300 W

• Maximum Insulation Voltage: 600 V (Marked on the ceramic body)

• Core Material: Refractory Ceramic

• Coating: High-Temperature Vitreous Enamel

• Mounting Type: Panel Mount (Center Shaft Mounting)

• Number of Terminals: 3 (Can be wired as either a potentiometer or a 2-wire rheostat, depending on the application.)

Frequently Asked Questions (FAQ)

4.47A2×15ΩQ: What is the actual power rating of this Ohmite Model N 15 Ohm Rheostat?
A: Although the nameplate specifies a 4.47 A current rating, applying Watt’s Law (P = I²R) results in a continuous power dissipation rating of 300 watts, assuming proper mounting and adequate ventilation for heat dissipation.

Q: What condition is the component in?
A: This is a used component sourced from a surplus equipment lot and does not include the original packaging. The wiper arm rotates smoothly, and the rheostat has been tested to verify continuous resistance across its full adjustment range, confirming there are no breaks in the wirewound resistive element and that it is fully functional.

Q: Can I use it as an audio potentiometer?
A: It is not recommended. Due to its wirewound construction and high-power rating, this rheostat is designed for industrial current control—such as DC motors, high-power lighting, heating elements, and load circuits—not for low-level audio signals. In audio applications, the wirewound element can introduce mechanical contact noise (“zipper noise”) and does not provide the smooth performance expected from audio-taper potentiometers.