Castair Open Drip Proof Motor — 3.5 HP, 208/230V, 1 Phase, Frame 56, 3450 RPM (3.5-56-1H)
The Castair 3.5-56-1H is the OEM replacement electric motor for Castair compressor models that use a 3.5 horsepower, single-phase motor in the 56-frame configuration. At 3450 RPM, this is a high-speed motor designed to drive a compressor pump through a matched pulley and belt system. The Open Drip Proof (ODP) enclosure is appropriate for indoor shop installations where the motor is not exposed to direct water splash or excessive airborne contamination.
Manufacturer page data was not available for this listing. Specifications are drawn from the product name and standard motor nomenclature. Call 866-217-0063 to confirm fitment with your compressor model before ordering.
Motor Specifications Explained
Reading the Motor Designation
- 3.5 HP: Rated output horsepower — this is the continuous-duty power output the motor is designed to deliver
- 208/230V: Dual-voltage input — motor can be wired for either 208V or 230V single-phase supply. Verify your shop supply voltage before installation.
- 1 Phase: Single-phase power — this motor does NOT run on three-phase power. Single-phase is standard for most shops without three-phase service.
- Frame 56: NEMA 56 frame — defines the physical mounting footprint, shaft diameter, and shaft height. A replacement motor must match the frame to fit the existing motor mount without modification.
- 3450 RPM: Synchronous speed (actual no-load speed; loaded speed will be slightly lower). This RPM is matched to the compressor pump's design speed through the pulley ratio.
- Open Drip Proof (ODP): Motor enclosure type — ventilated for cooling, protected against drips from above, but not sealed against dust or splashing water
NEMA 56 Frame Dimensions
- Shaft Height: 3.5 inches (center of shaft to mounting base)
- Mounting Pattern: NEMA 56 standard — 4-bolt face or foot mount depending on configuration
- Shaft Diameter: Standard NEMA 56 shaft — confirm exact diameter (typically 5/8") with the compressor service manual
- Any replacement motor must match the NEMA 56 frame spec to drop into the existing motor base without drilling new holes or shimming
When You Need This Motor
Replacement Scenarios
- Motor failure: Burned winding, shorted capacitor, seized bearings — when the motor is beyond economic repair and you need an OEM replacement that matches the original specs exactly
- Upgrade: Replacing an underpowered or damaged motor on a compatible 56-frame compressor base with the OEM-spec unit
- Reconditioning: Bringing a used Castair compressor back to service with a fresh motor that matches the original electrical and mechanical spec
When NOT to Use This Motor
- If your compressor runs on three-phase power, this single-phase motor will not work — you need a three-phase motor with the matching HP and frame
- If your supply voltage is 460V or 480V, this motor is not rated for that voltage
- If your compressor uses a different frame size (143T, 145T, 182T, etc.), the mounting will not fit without modification
Installation Considerations
- Pulley: The existing motor pulley should transfer to the new motor if shaft diameter matches — confirm shaft diameter before installation
- Belt: Inspect and replace the drive belt when replacing the motor — a worn belt on a new motor will wear it prematurely
- Capacitors: ODP single-phase motors use a start capacitor (and sometimes a run capacitor). Confirm these are included with the motor or order separately if needed.
- Wiring: Verify supply voltage and wire the motor accordingly — 208V and 230V wiring configurations on dual-voltage motors use different connection patterns
- Rotation: Verify the motor rotates in the correct direction for your compressor pump before final installation
What's in the Box
- 1x Castair ODP replacement motor, 3.5 HP, 208/230V, 1Ph, Frame 56, 3450 RPM
- Note: Capacitors, pulleys, belts, and mounting hardware are NOT included unless specified — order separately if needed
Technical Specifications
- Part Number: 3.5-56-1H
- Horsepower: 3.5 HP
- Voltage: 208/230V single-phase
- Phase: 1-phase
- NEMA Frame: 56
- Speed: 3450 RPM
- Enclosure: Open Drip Proof (ODP)
- Price: $352.43
Why Buy From OEM Diagnostic Tools?
- Specialist since 2016 in air compressor parts and major components
- Free shipping on qualifying orders
- Free tech support at 866-217-0063 — confirm motor specs and fitment before ordering. Motor returns are more complex than small parts; get it right the first time.
- Full manufacturer warranty on Cast Air motors
- Honest guidance: If your compressor needs a different frame or phase configuration, we will tell you before you buy the wrong motor
Call 866-217-0063 for quick answers and help!
