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Monday, May 07, 2012

Live AC 120

First, let me say that I 'punted' on the Blue Seas custom 360 panel idea (previously mentioned here). As much as it was fun to design, and would look cool, it would not be flexible enough for this project. The original idea had the panel designed for future appliances that we may or  may not install. Logic stepped in and asked "what if you change your mind?, what if you never install these devices?" So I took a look at other off-the-shelf panel options.
Test fitting the freshly cut panel frame.
I concluded that using the "traditional metal" panel designs would be more flexible, and maybe even cheaper in the long run. The idea is to start with basic needs, and expand as devices are added. There is plenty of panel space in the engine room, and I have designed the space with "easy reconfiguration" features in mind. This should be better than trying to predict future needs, with one big panel, all at once (especially knowing us).
Shore power AC panel and meter showing AC current.
So, with all that, the first AC panel is in and live. This as a Blue Sea Systems "traditional metal" panel that  includes one 30A ELCI master shore power switch, and five positions for breakers. Two of these five have 15A breakers: one for 'AC Outlets', the other for 'Battery Charger' (coming soon). Also added is a digital multimeter for measuring AC voltage, current and frequency. Chaining more panels to this one, if necessary, is quite easy. Mounted on the same frame are two duplex outlets supplying power needs for workbench projects. One of these is a GFCI outlet behind which are wired ALL of the AC outlets throughout the boat.
Panel hinges down for easy access.
The panel frame is hinged at the bottom allowing easy access for reconfiguration and circuit additions.

Finished install. Meter is showing AC voltage.
I had previously wired AC sockets throughout the boat. I also ran wire for the "future" appliances. Until such appliances are installed (if ever) their wire feeds will simply be terminated with another AC socket. This means, you are ALWAYS in reach of a live AC socket. No need for an extension cord! So now the growing spider web of extension cords can be removed, much to the relief of my local fire marshal.
A motivating goal: removal of the rat's nest of extension cords.
GFCI or ELCI?

Readers have probably heard of GFCI outlets. GFCI stands for "Ground Fault Circuit Interrupter". One commonly sees these sorts of outlets in house bathrooms and lavatories (squarish looking outlets, with red and black buttons, sometimes). GFCI outlets provide fire hazard safety such that they can detect an "electrical short" to ground (green wire) and automatically switch off the circuit in such an event.

ELCI, stands for "Electrical Leakage Circuit Interrupter", and goes one better than GFCI. These switches, installed between the shore power connection and AC distribution panel,  monitor current flow on the HOT (black) and NEUTRAL (white) lines of an AC circuit. Physics asserts that the sum current of both sides must be equal to zero at any given time (current in, must equal current out). Any electrical leak will create an imbalance (non-zero sum) detected by the ELCI cutting off the circuit (within a 30 milli-amp tolerance, typically). A short to the ground wire (green) creates such an imbalance and qualifies as an electrical leak, thus ELCI provides the same protection as GFCI.

ELCI switches are more expensive than GFCI switches. So, why not just use a GFCI? Well, when the boat is connected to shore power, protection by a GFCI  is only as good as the wiring of the dock's shore power system. All marina shore power wiring can vary in quality (despite local codes). If the ground of the dockside shore power socket has poor or no earth ground, a GFCI will provide NO protection AT ALL.

On a boat, there are more potential paths to earth ground than the shore power's green wire. The boat's bonding system, to metal thru-hulls, to seawater is a common point of electrical leakage faults. Such faults can cause lots of problems not only for your boat's underwater metals (thru hulls and zinc anodes), but those of neighboring boats as well. And any diver, changing zincs underwater, in the vicinity of such a fault, may not be having a great time either.

An ELCI installed on the boat, between the shorepower connection and AC distribution will protect against these faults. Shore power connection ELCIs are now required as part of the ABYC E-11 specification. If you have a steel or aluminum boat, an ELCI is an absolute MUST in my opinion.


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