Friday, February 1, 2013

Some features of our boat's DC and AC Electric system

In this post ( ) I talked about how we are able to service 63A of devices with a single 30A shore power cord.  There are a couple of other features baked into Viking Star's electrical system.  Perhaps these can be useful to others.

A few items of note:
  • 25A Shore-power Circuit Breaker.  Idea here is we pop this breaker before the 30A one on shore pops.  (Cause you know that one on shore will only trip when it is dark.  And Cold.  And Raining. . .)
  • Isolation Transformer:  Rather uncommon , but absolute solution for galvanic isolation.  This one has taps to compensate for low dock-voltage situations as well as being able to be serviced by a 220-250V sources (ala, outside of North America)
  • Dual inverter/chargers:  Redundancy.  Allows for the 63A/30A magic.  Can be used to service the boat / batteries from a 50hz service while providing 60hz power on the boat.
  • Dual DC system:  Engine and House.  Each totally independent with their own charging sources (alternators on Mains).
  • Split DC distribution and A/B switch:  House panel serviced directly by the House battery, while the Navigation panel can pull from House or (as a backup) the Engine battery.  This same A/B switch allows for bridging of the two DC systems in case of a fault say in one of the alternators or a need for a 'boost' in starting.
  • The fusing on the 270A house alternator:  It is rather common to just connect alternators directly to batteries w/o any fusing.  Much like how the starter alternator is done on Viking Star.   However I do have a fuse here primarily because of the distance from the battery compartment to the engine compartment.   The fuse is located at the battery and is there in case some short happens to the wire on its way to the 270A alternator.  Yes, does present a risk to the alternator when (if) the fuse blows - but that will be the lesser of two evils if some failure mode occurs which cases the fuse to go. . . .

Of these I would say I like the 25A mains breaker and the dual DC system w/the A/B switch on the Navigation panel the best.

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