The Castair S104 is the OEM magnetic motor starter for 10 HP, 460-Volt, three-phase Castair piston air compressors. The S104 is the 460V equivalent of the S102 (208/230V, 3-phase, 10 HP) — same horsepower and phase, higher voltage. At 460V, the motor draws approximately half the current of the 208/230V equivalent for the same power output. That means smaller wire gauge in the motor circuit, smaller contactor contacts, and smaller overload heater elements — in this case, three B25 heater elements versus the B45 elements used in the S102.
460V Operation — Why It Matters for Larger Shop Installations
460V three-phase is the standard industrial voltage for larger shops, manufacturing facilities, and any installation where long wire runs between the panel and the compressor would cause significant voltage drop at 230V. If your facility has 460V three-phase available and your compressor is rated for it, there are clear advantages:
- Half the current draw at the same HP — smaller wire, smaller breaker, less heat in the circuit
- Better voltage stability over long runs — less voltage drop means the motor gets closer to its rated voltage
- Lower contact wear on the starter contactor — lower current means less arcing at each start
The S104 is the correct starter for 460V-rated Castair compressors. Do not use a 230V starter on a 460V circuit — the contactor and overload elements are not interchangeable.
Heater Element Specification
Three B25 heater elements required — one per phase. The B25 is sized for the lower per-phase current drawn by a 10 HP motor at 460V versus 230V. The overload relay trips if any phase draws current above the heater's rated threshold, protecting against phase loss, overload, and locked rotor conditions.
Castair Starter Lineup — 460V Three-Phase Models
- S54 — 5 HP, 460V, 3-phase, heater: B11.5 (×3)
- S74 — 7.5 HP, 460V, 3-phase, heater: B22 (×3)
- S104 (this unit) — 10 HP, 460V, 3-phase, heater: B25 (×3)
- S154 — 15 HP, 460V, 3-phase, heater: B32 (×3)
- S204 — 20 HP, 460V, 3-phase, heater: B40 (×3)
Technical Specifications
- Part Number: S104
- Motor Horsepower: 10 HP
- Voltage: 460 Volt
- Phase: 3-Phase
- Overload: Included
- Required Heater Elements: B25 — qty 3 (one per phase)
- Manufacturer: Cast Air
Why Buy From OEM Diagnostic Tools?
OEM Castair magnetic starters — correct 460V contactor rating and B25 overload heater specification. Free shipping on qualifying orders. Free tech support at 866-217-0063. Full Castair manufacturer warranty. Call us if you need the B25 heater elements included with your order.
Call 866-217-0063 for quick answers and help!
