The Castair S152 is the OEM magnetic motor starter for 15 HP, 208/230-Volt, three-phase Castair piston air compressors. The S152 is the three-phase 208/230V entry point for 15 HP motor protection — a step up in contactor capacity from the 10 HP S102, with three B70 heater elements for three-phase overload protection at this current level. Castair specifies quality name-brand, off-the-shelf magnetic starters for all their compressors so technicians can source, replace, and service them without proprietary components or dealer callouts.
Why 15 HP Demands a Properly Rated Starter
A 15 HP motor at 208/230V three-phase draws approximately 40–42 amps full load. Starting inrush can be 6–7 times that — 240–290 amps for the brief starting interval. The S152's contactor is rated to close against that inrush without contact welding or damage. The overload relay with B70 heater elements monitors per-phase running current and trips if the motor overloads — from a stuck unloader, seized pump, low voltage condition, or phase loss. A properly sized and functional starter is what stands between a $500 motor repair and a $2,500 motor replacement when something goes wrong.
Heater Element Specification
Three B70 heater elements required — one per phase. Note that the B70 is the same heater element used in the single-phase S101 (10 HP, 230V, 1-phase), but the S152 requires three of them for three-phase coverage. The B70 is sized for the per-phase current of a 15 HP three-phase motor at 208/230V. Verify the motor's nameplate FLA against the overload relay chart if your motor's amperage differs from standard.
Castair Starter Lineup — 208/230V Three-Phase Comparison
- S52 — 5 HP, 208/230V, 3-phase, heater: B25 (×3)
- S72 — 7.5 HP, 208/230V, 3-phase, heater: B36 (×3)
- S102 — 10 HP, 208/230V, 3-phase, heater: B45 (×3)
- S152 (this unit) — 15 HP, 208/230V, 3-phase, heater: B70 (×3)
- S202 — 20 HP, 208/230V, 3-phase, heater: CC87.7 (×3)
- S252 — 25 HP, 208/230V, 3-phase, heater: CC132 (×3)
For 460V three-phase 15 HP applications, see the S154 with B32 heater elements. Verify your supply voltage before ordering — a 230V starter used on a 460V circuit will fail immediately and may cause a motor fault.
Installation Notes
- Three B70 heater elements required (sold separately or ask us to include them)
- Verify supply voltage is 208V or 230V three-phase before installation
- Pressure switch connects to the magnetic coil circuit, not the load terminals
- Mount in original enclosure; connect to same terminal designations as the failed starter
- Test overload reset after installation before returning compressor to service
Technical Specifications
- Part Number: S152
- Motor Horsepower: 15 HP
- Voltage: 208/230 Volt
- Phase: 3-Phase
- Overload: Included
- Required Heater Elements: B70 — qty 3 (one per phase)
- Manufacturer: Cast Air
Why Buy From OEM Diagnostic Tools?
OEM Castair magnetic starters with the correct contactor rating and overload relay for 15 HP three-phase operation. Free shipping on qualifying orders. Free tech support at 866-217-0063. Full Castair manufacturer warranty. Ask us about including the three B70 heater elements with your starter order.
Call 866-217-0063 for quick answers and help!
