Power and Grounding Considerations 4.1.3 Circuit Protection Each of these four un-switched battery (+) inputs requires a 10 Amp circuit breaker rated for a continuous duty load of 7 Amp at 12 or 24 VDC. Powering the ECU through dedicated circuits with circuit breakers reduces the possibility of degradation of electronic control system performance. This also minimizes the chance of an engine shutdown due to a short in the electrical system. Additional loads should not be connected between the ECU and the circuit protection for the ECU. Circuit protection wiring is illustrated in Figure 1. Caterpillar prefers the circuit protection to be located in the machine cab (if applicable).
If not in the cab, for ease of service, the circuit protection should be located in an easily accessible and documented location. NOTE: DO NOT use in-line fuses for circuit protection. Caterpillar recommends the use of circuit breakers for circuit protection. Circuit breakers should be located with other circuit protection in a centrally located, dedicated panel. If circuit breakers that automatically reset are used, consideration of the environment of the location of the breaker is critical and the effect on the trip point is critical. The trip point of some circuit breakers can be significantly reduced below the rated trip point if the circuit breaker is exposed to high temperatures.
This can cause intermittent shutdowns that result in the needless replacement of electronic components. Figure 1: Battery (+) Wiring and Circuit Protection Diagram P1/J1 ECU 10 A 10 A 10 A 10 A Key Switch Engine Battery Master Disconnect Switch Chassis NOTE: For already installed Tier 3 and earlier applications, four un-switched positive battery connections and four ground connections are recommended but not required. New installations, especially those with HEUI fuel systems, should be designed with all four un-switched positive and negative battery connections. NOTE: For already installed Tier 3 and earlier applications, a single 25 Amp circuit breaker was used.
New installations, especially those with HEUI fuel systems, should be designed with four individual 10 Amp circuit breakers. NOTE: Petroleum ATEX and rail head end power applications have additional power and grounding requirements. Contact Caterpillar Application and Installation Engineering for wiring and circuit protection for these applications. I N D U S T R I A L E N G I N E E L E C T R O N I C S 20 48 52 53 55 70 61 63 65 69 Un-switched Battery (+) Un-switched Battery (+) Un-switched Battery (+) Un-switched Battery (+) Switched Battery (+) Un-switched Battery (-) Un-switched Battery (-) Un-switched Battery (-) Un-switched Battery (-)