Fuses Marine Rated Battery Fuses

MRBF Terminal Fuse - 125A

5184
  • Requires the use of Terminal Fuse Blocks PN 5191 or PN 2151—do not mount the fuse directly to the battery terminal
  • Interrupt rating satisfies ABYC requirements for DC Main circuit protection on large battery banks
  • Ignition protected—safe for installation aboard gasoline powered boats
  • Clear window—visual indication of blown condition
  • Color coded for each amperage
MSRP: $18.29
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Frequently Asked Questions

Q: Are fuses and circuit breakers interchangeable?

A:
The short answer is yes. The longer and more accurate answer is more complex and beyond the scope of this discussion. As amperage ratings increase, circuit breakers become relatively more expensive than fuses. Generally, fuses are less expensive for a given rating, but circuit breakers are re-settable and don’t require the purchase of spares, as do fuses. Also, circuit breakers can be used as switches.

Q: How do fuses and circuit breakers differ?

A:
Fuses are thermal devices that open the circuit by utilizing a “fusible link” that melts at a known amperage in a known length of time. Circuit breakers can be either thermal or magnetic devices or a combination of the two.

Q: How does the CPD (Circuit Protection Device) stop the amperage flow?

A:
There are two primary methods that CPD’s use to determine that excess amperage is flowing in a circuit. Thermal devices open to break the circuit and stop the current flow in response to heat generated by the excess amperage. Magnetic devices react to a magnetic field created by excess amperage.

Q: Why is Opening Speed Important?

A:
When a circuit is activated, there is an initial surge of current (amperage) that the CPD must allow to pass without tripping the CPD. The two screen reprints below from the Blue Sea Systems’ testing system illustrate the difference in inrush currents between inductive (like motors) and resistive (like light bulbs) loads.

Notice that the ratio of normal running current (represented by the flat portion of the amperage line) between the inductive and the resistive graphs varies dramatically. The 17A inductive load initially drew 80 A or 470%, whereas the 44A resistive load initially drew only 126A or 286% of its normal operating current. Such inrush currents must be ­considered when sizing CPD’s. Each Blue Sea Systems’ CPD has a time/current chart shown on its catalog page.

We recommend sizing fuses and circuit breakers for 5X multiples for inductive loads and 3X multiples for resistive loads and assuming this inrush for approximately .5 seconds.

Inductive Load
Resitive Load

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