Circuit Breakers 285-Series

285-Series Circuit Breaker - Panel Mount 40A

7082
  • Drop in replacement for 185-Series Circuit Breakers
  • Visible reset lever shows open condition
  • Ignition protected - Safe for installation aboard gasoline powered boats
  • Meets SAE J1171 external ignition protection requirements
  • Weather Resistant
  • Combines switching and circuit breaker function into one unit*
  • "Trip Free" - cannot be held closed after trip
* Do not use as a switch where high inrush currents are expected.
MSRP: $58.99
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Frequently Asked Questions

Q: What size CPD (Circuit Protection Device) is required?

A:
The short answer is that the CPD (Circuit Protection Device) should be rated to open at an amperage that is greater than the maximum load the circuit will carry and smaller than the rated amperage capacity of the wire in the circuit. We recommend choosing a size as close to, but not greater than, the amperage capacity of the wire.

Use our Circuit Wizard to find what circuit protection would work best for your application.

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: Are thermal circuit breakers appropriate for marine use?

A:
Yes. It is sometimes argued that this circuit breaker type is inappropriate for marine use because it is affected by temperature—that is, the hotter the ambient environment (such as an engine room) the lower the amperage at which the device will open, leading to undesired trips. The percentage by which the rated amperage lowers in normal operating environments is usually in the 10 to 20% range and when properly sized the risk of “nuisance trips” is remote.

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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