Castair 7.5 HP Single-Phase Electric Motor — Frame 215T, 1725 RPM, 208/230V (Part# 7-215-1)
If your shop runs on single-phase power and you need to drive a serious industrial air compressor, the Castair 7-215-1 is one of the few motors that can actually do the job. At 7.5 horsepower in a 215T frame, running at 1725 RPM, this motor is built for shops that have outgrown smaller compressors but either do not have three-phase service or do not want the cost and complexity of a phase converter. It is a substantial piece of equipment — 145 pounds of cast iron and copper — and it will outlast cheaper import motors by a wide margin.
This is the motor Castair specifies for their larger cast iron two-stage compressors. When you are looking at a cast iron pump running at industrial duty cycles, this is the motor category that keeps up with it. If you are rebuilding a worn-out compressor unit or upgrading a smaller motor on an existing tank, the 7-215-1 gives you the horsepower headroom to handle long run cycles without overloading.
Motor Specifications
- Part Number: 7-215-1
- Horsepower: 7.5 HP
- Phase: Single-phase (1Ph)
- Voltage: 208/230V (dual voltage)
- Amperage Draw: 38A at 208V / 36A at 230V
- Frame Size: 215T (NEMA standard)
- RPM: 1725
- Shaft Diameter: 1-3/8 in
- Service Factor: 1.15
- Weight: 145 lbs
- Enclosure: Open Drip Proof (ODP)
- Certifications: UL and CSA listed
Why 1725 RPM Matters on a Compressor Motor
The 1725 RPM rating is not a limitation — it is an engineering decision. Castair designs their cast iron two-stage pumps to run at slow speeds specifically because slower operation means lower heat, less wear, longer valve life, and quieter operation compared to a 3450 RPM motor pushing a smaller pump harder. A 7.5 HP motor at 1725 RPM turning a correctly matched cast iron pump will outlast a 5 HP motor screaming at 3450 RPM on a cheaper aluminum pump. This is the principle behind quality industrial compressors versus the box-store units.
The 215T frame is the largest frame Castair offers in single-phase. It is a genuine industrial frame size — not a homeowner or light-commercial motor. The 1-3/8 in shaft handles the belt loads from large cast iron pump sheaves without deflection issues that plague smaller shafts on high-torque applications.
Single-Phase vs. Three-Phase at 7.5 HP — What You Need to Know
Three-phase power is more efficient at this horsepower level. Castair also offers a 7.5 HP three-phase motor (part# 7-213-3) that draws only 23/22/11 amps depending on voltage, compared to 38/36 amps for this single-phase unit. If you have three-phase service, the three-phase motor is the right choice.
But most small to mid-size shops do not have three-phase. Running a rotary phase converter adds cost and maintenance. This single-phase 7.5 HP motor is the answer for shops that need real horsepower from standard utility power. The 38-amp draw at 208V means you need a properly sized 50-amp dedicated circuit — this is not a motor you plug into a standard outlet. If your electrical panel cannot support that load, a 5 HP single-phase motor (part# 5-184-1, 22 amps) may be a better fit.
Open Drip Proof Enclosure
The ODP enclosure is appropriate for compressor rooms that are sheltered from direct water spray and blowing rain. It allows air circulation through the motor windings, which helps with cooling under sustained load. If your compressor is outdoors or in a wet environment, you need a TEFC (totally enclosed fan-cooled) motor instead — contact us and we can discuss alternatives. For a typical shop compressor installation in a garage, shop, or equipment room, ODP is the standard choice.
Installation Considerations
- Circuit requirement: 50-amp dedicated single-phase circuit minimum at 230V
- Wiring: This motor must be wired to a magnetic starter with overload protection — do not run direct from a breaker
- Belt drive: 1-3/8 in shaft accommodates standard B and C section V-belts for large pump sheaves
- Mounting: 215T frame uses standard NEMA bolt pattern — confirm pump base dimensions before ordering
- Weight: At 145 lbs, plan for proper rigging and two-person installation
- Rotation: Verify rotation direction matches your pump's requirement before running under load
Where This Motor Fits in the Castair Lineup
Castair offers single-phase motors from 2 HP (part# 2-56-1H) through 10 HP (part# 10-215-1). The 7.5 HP 215T at 1725 RPM is the second-largest single-phase option. Here is how the upper range compares:
- 7.5 HP / 184T / 3450 RPM (7-184-1H): 95 lbs, 34/31A draw — higher speed, smaller frame, lighter
- 7.5 HP / 215T / 1725 RPM (7-215-1): 145 lbs, 38/36A draw — slow speed, industrial frame, built for heavy duty
- 10 HP / 215T / 1725 RPM (10-215-1): 165 lbs, 46/43A draw — maximum single-phase option, requires 60-amp circuit
The 7-215-1 is the right choice when you need real slow-speed industrial performance on single-phase power. The 184T frame at higher RPM works for lighter-duty applications. The 10 HP 215T is for shops running continuous heavy production loads.
When Does a Shop Need This Motor vs. Stepping Up or Down
Choose this motor if: You are running a cast iron two-stage pump in the 15-25 CFM range on single-phase power, your shop does production sandblasting, spray painting with continuous demand, or multiple air tools running simultaneously, and you have a 50-amp dedicated circuit available.
Step down to 5 HP if: Your compressor handles intermittent use — a few air tools, occasional spraying, tire inflation. A 5 HP motor at 22 amps is far more manageable electrically and will run a cast iron pump adequately for light to medium shop use.
Step up to 10 HP (single-phase) or 7.5 HP (three-phase) if: You are running a production facility with near-continuous air demand, or you have the three-phase service to take advantage of the efficiency improvement.
Why Buy From Air Compressor Factory Direct?
- Castair specialists: We know this product line inside and out — specs, compatibility, installation requirements
- Free shipping on orders that qualify — on a 145-lb motor, that matters
- Free technical support: Call us before you order to confirm frame, shaft, and electrical compatibility with your existing equipment
- Full manufacturer warranty: Sold as Castair intended, with full warranty support
- No upselling: If the 5 HP motor is the right answer for your application, we will tell you
Call 866-217-0063 for quick answers and help!
