Overview
The Siemens 42AF35AF is a Class 42 definite purpose contactor engineered for straightforward motor control in HVAC systems, pump applications, and light industrial motor circuits. With its 25 amp rating, 600 VAC coil-to-load voltage, and 110/120 VAC control coil, this 3-pole open-frame contactor delivers dependable switching with minimal maintenance. Manufactured under the Furnas Electric Co. brand (now Siemens Energy & Automation), the 42AF35AF maintains compatibility with legacy installations while remaining a drop-in solution for systems originally specified with this model.
Key Features
- Weld-resistant silver cadmium oxide contacts — Superior electrical durability and reduced contact erosion under inductive loads.
- Compact open-frame design — Easy field access for inspection and maintenance; interchangeable mounting on durable metal backplate.
- Quiet operation — Cushioned coil and precision-fit assembly reduce mechanical noise and vibration.
- Visual contact position indication — Operator can verify load status without electrical test equipment.
- Snap-on electrical/mechanical interlocks — Optional field addition for reversing or multi-function control circuits.
- Double quick-connect terminals — Standard termination reduces installation time and field wiring errors.
Technical Specifications
Rated load current: 25 A FLA (full load amps)
Voltage across load poles: 600 VAC
Horsepower ratings (3-phase): 5 hp @ 240 V; 7.5 hp @ 480 V; 7.5 hp @ 600 V
Horsepower ratings (1-phase): 2 hp @ 120 V; 3 hp @ 240 V
Control coil voltage: 110–120 VAC, 50/60 Hz
Pole configuration: 3 pole, 3-position (open/closed)
Contact configuration: 4NO–4NC (four normally open, four normally closed auxiliary contacts optional)
Enclosure: Open (snap-on DIN rail mount optional)
Operating temperature range: –40 °C to +70 °C (–40 °F to +158 °F)
Termination: Quick-connect push terminals (SEMS or lug options available)
Typical Applications
- HVAC unit fan motor control and compressor switching
- Centrifugal and reciprocating pump motor circuits
- Light industrial machinery start/stop control
- Water heater and boiler burner motor circuits
- Chiller and air-handling unit switching in building automation
Compatibility & Replacements
The Siemens 42AF35AF is a Class 42 definite purpose contactor from the Furnas Electric Company product line, now part of Siemens. While the unit is no longer in active production, authorized replacement options include the Eaton C25DND325A, which maintains electrical and mechanical interchangeability for new installations. For legacy system maintenance, the 42AF35AF remains the preferred reference standard; stock units are available through authorized electrical distributors. Verify coil voltage and terminal type before substitution.
