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1.2.1 Circuit Breakers

Overview

All START battery positive circuits protected by Mechanical Products Series 17 circuit breakers with direct battery connections.

Location: Wheel well, within 7" of START battery positive terminal (ABYC/NEC code compliant)

Circuit Breaker Specifications

Circuit Model Rating Reset Type Power Path Max Load Sizing
PMU24 Mechanical Products
(174-S2-250-2)		 250A Manual START battery+
└→ 250A CB
   └→ PMU24		 ~253A theoretical peak (140-170A typical) 99% of max load (with all radios transmitting + full radiator fan)
BCDC Input Mechanical Products
(174-S2-080-2)		 80A Manual START battery+
└→ 80A CB
   └→ BCDC Alpha 50		 50-55A BCDC input 145-160% of max load

Total Circuit Breakers: 2 (PMU 250A, BCDC 80A)

PMU Circuit Breaker Sizing

250A CB sized to protect 2/0 AWG wire (265A @ 60°C). Typical PMU load is 140-170A (56-68% of CB rating). The 253A theoretical peak requires all loads maxed simultaneously - not realistic in practice.

All Circuit Breakers:

  • Manufacturer: Mechanical Products Series 17
  • Type: Surface mount
  • Reset: Manual (Type III - push to reset)
  • Terminals: 3/8"-16 studs (S2 configuration)
  • Dimensions: 3.39" L × 1.9" W (per unit)
  • Ratings: 48V DC (20-150A), 30V DC (175-200A), 14V DC (225-300A)
  • Standards: Marine-rated (SAE J1171, ABYC E-11, UL1500, IP67, MIL-STD-202)
  • Mounting: Wheel well within 7" of battery positive terminal

Space Requirements: 2 CBs side-by-side with wiring clearance for 2/0 AWG cables: ~7" × 4" (~28 sq in)