Quote:
Originally Posted by thinwater
Noelex:
On most boats, breakers are used as switches, or at least many are. For example, that is typically the only way to turn on running lights or the anchor light. That's not really what breakers are for, but that is what is commonly done.
While a DIN rail mount is neat, in industry they are always in cabinets, to keep untrained fingers out, and the switches are elsewhere. Is that the case for you?
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Switching DC is difficult. In simple terms, a small spark is created when the circuit is broken. This erodes the contact surfaces of the device (circuit breaker or switch) that is responsible for breaking the circuit. Switching AC (alternating current) is actually much easier, as the spark is naturally extinguished when the voltage passes through zero.
The low voltage of
marine systems helps reduce the spark size, but also means any slight deterioration of the contact surfaces caused by the arching will result in more resistance causing a higher percentage voltage drop. This is one of the common reasons why pleasure
boat marine
electronics tends to produce so many problems. At 12v all contacts have to be close to perfect.
Switches are much cheaper than circuit breakers. The common pleasure boat marine solution especially in recent years is to use a small number of circuit breakers and a large number of switches. The switch and associated
wiring introduces additional failure points and reduces redundancy (because a
single circuit breaker failure or fault that trips the circuit breaker will take out multiple systems). Even worse, some of these switch
panels use proprietary breakers that are very hard to replace, even assuming you can still find the identical breaker in future years.
If you have one of these systems you need to be careful about switching devices off and on under load using the circuit breakers, although it not always possible to avoid this. Using a switch means the contact surface damage is transferred to the switch itself, but at least switches are (usually) more easily replaced and you are likely to be able to find a similar replacement when the time comes.
The Blue Seas switch panels are better. It is fiddly, but the circuit breakers can be unscrewed and replaced. Their popularity helps ensure replacement
parts will be available in the future.
The DIN rail circuit breakers are better again. They are very easy and quick to replace (it only takes a couple of minutes).
Replacements will always be available as identical products are made by multiple manufacturers. So I have no concerns about using them as a switch. This simplifies the circuit and reduces the number of failure points, especially when the associated interconnecting wires and contacts between the circuit breaker and switch are taken into account. The industrial circuit breakers are ruggedly constructed with large contact surfaces (this does make them physically large, which is a drawback given the limited space allocated for most switch panels). They should endure switching under load better than marine switches. The extra cost of multiple circuit breakers is not insignificant, but reliable
electronics is tough to achieve in the marine
environment, so I feel the extra cost is justified.