Passage Maker - - News & Notes -

you have had trou­ble lately plug­ging into shorepower, you are not alone. What used to be a rel­a­tively sim­ple and re­li­able pro­ce­dure has be­come a bit of a guess­ing game with new reg­u­la­tions aimed at re­duc­ing risk of elec­tric shock, both to those on­board and those swim­ming near boats in mari­nas. While the tran­si­tion will take some time to adapt to, it will ul­ti­mately save lives. Let’s look into the rea­son­ing be­hind the change, the new tech­nol­ogy, and what you can do to avoid prob­lems with your shorepower setup at mari­nas.

For the last 30 to 40 years, most boats have been built with pro­tec­tive mea­sures such as re­versed po­lar­ity warn­ing de­vices. Th­ese de­vices, com­bined with wiring stan­dards, greatly re­duce the risk of elec­tro­cu­tion while on­board a ves­sel plugged into shorepower. Over the past decade, much knowl­edge has been gained about a tragic sit­u­a­tion now known as elec­tric shock drown­ing (ESD). We now un­der­stand why many peo­ple, es­pe­cially chil­dren, have drowned when swim­ming near boats (or in swim­ming pools). Many of th­ese deaths ini­tially ap­peared to be sim­ple cases of drown­ing. But what we have learned is that while th­ese peo­ple did die from drown­ing, they drowned be­cause elec­tric­ity in the wa­ter caused a loss of mus­cle con­trol.

How does the elec­tric cur­rent en­ter the wa­ter in th­ese cases? It can come from boats or from ma­rina wiring. AC cur­rent (shorepower), will al­ways re­turn to its source, by all avail­able means. How much trav­els through each avail­able path de­pends on the con­duc­tiv­ity of each path. For shorepower, the source is the power sta­tion some­where on­shore. Once elec­tric­ity finds its way into the wa­ter it will seek a path through the wa­ter back to shore. If a path with less re­sis­tance be­comes avail­able, more cur­rent will flow into that path.

Salt wa­ter has bet­ter con­duc­tiv­ity than fresh wa­ter. Pic­ture a boat, with an elec­tri­cal fault, tied to the dock in a fresh­wa­ter en­vi­ron­ment. The wa­ter around that boat be­comes “charged” with the po­ten­tial of AC cur­rent try­ing to get to the shore­line or the dock. The hu­man

If­body has higher salin­ity than fresh wa­ter (think about the salti­ness of sweat). If you swim into that field of charged wa­ter, your body be­comes a pre­ferred path. If enough cur­rent goes through your body, you lose mus­cu­lar con­trol and will likely drown as a re­sult. Swim­ming in salt wa­ter changes the equa­tion and greatly re­duces the risk, but in brack­ish wa­ter the un­cer­tain­ties are life threat­en­ing. Bot­tom line: Don’t swim in mari­nas. Typ­i­cal shorepower, 120-volt al­ter­nat­ing cur­rent (120V AC), re­lies on three wires: black (hot), white (neu­tral), and green (ground­ing). The black wire works in con­cert with the white to bring the shorepower to your boat. If all goes ac­cord­ing to plan, the green wire will never carry any cur­rent or do any “work.” The green wire is like a res­cue squad that rarely gets a call, but if the call comes in, it can save your life.

Let’s look at a ba­sic shorepower wiring di­a­gram. In this draw­ing (fig. 1) we can see that the hot and neu­tral wires bring shore power to the ap­pli­ances. The green wire is on “standby,” with no cur­rent flow­ing through it. If cur­rent does flow in the green wire, a “ground fault” has oc­curred. We’ll ex­plain that green wire to the en­gine in a mo­ment.

If the black wire in­side the mi­crowave chafes from years of boat move­ment (fig. 2), it might even­tu­ally make con­tact with the outer cas­ing. The out­side of the mi­crowave then be­comes “hot” and if touched might lead to a fa­tal shock. To pre­vent against this risk, the green wire has been at­tached to the case, pro­vid­ing a bet­ter path back to shore than of­fered by your body. But what if an AC hot wire shorts to a DC com­po­nent? To pro­tect you from a shock, the green ground­ing wire must be con­nected to all DC hard­ware as well. That, in part, is what the green wire at­tached to the en­gine ac­com­plishes. Fur­ther­more, if AC shorts to DC, and if DC is con­nected to all thruhulls through the bond­ing sys­tem (we’ll leave the dis­cus­sion of bond­ing sys­tems for an­other day), then underwater met­als

can be­come charged with AC volt­age, cre­at­ing an ESD haz­ard. Con­nect­ing the green ground­ing wire to the underwater hard­ware pro­tects against this dan­ger. As we can see in the il­lus­tra­tion ( fig. 2), the green wire takes the bulk of the ground fault safely ashore, with a trace amount go­ing in the wa­ter.

Be­fore mov­ing on, we need to look at one more pos­si­bil­ity (fig. 3): a fault in the green ground­ing wire. A bro­ken wire or loose con­nec­tion on the boat or on the dock could elim­i­nate the green wire from the cir­cuit. Now the green ground­ing wire con­nected to the en­gine and underwater hard­ware acts like a dou­ble-edged sword, di­rect­ing dan­ger­ous AC cur­rent into the wa­ter and cre­at­ing a se­ri­ous ESD haz­ard.

Pro­tec­tive de­vices come in a va­ri­ety of forms with vary­ing pur­poses, but they all work on the same prin­ci­ple: They de­tect a ground fault and break the cir­cuit. All of them are in­tended to pro­tect you from fa­tal shock.

In the chart (fig. 4), mA refers to mil­liamps. 5 mil­liamps would be ex­pressed as .005 amps or 5mA. As you read through the fol­low­ing list of pro­tec­tive equip­ment, re­fer to the chart above:

(GFCIs): We have th­ese at home and on boats, wher­ever you might plug in a de­vice such as a toaster or hair dryer in po­ten­tially wet lo­ca­tions (kitchens/ gal­leys, bath­rooms/heads, out­doors). GFCIs pro­vide pro­tec­tion only at the spe­cific lo­ca­tion. Th­ese trip at 5 mA.

Equip­ment In­ter­rupters (ELCIs): Th­ese de­vices pro­tect the whole boat. When a fault oc­curs a GFCI will shut down the af­fected area while an ELCI will shut down the boat’s en­tire shorepower sys­tem. Th­ese trip at 30 mA. Not all shorepower faults will man­i­fest at a GFCI re­cep­ta­cle: You might have a hot wire that chafes through on equip­ment not plugged into a GFCI re­cep­ta­cle. The ELCI will de­tect such a fault and shut down the boat. How­ever, be­cause of the ELCI’s higher thresh­old, GFCI re­cep­ta­cles are still needed. ABYC im­ple­mented the ELCI re­quire­ment in 2008 but un­til 2014 it was some­what loosely ap­plied. All ABYC-com­pli­ant boats built af­ter 2014 (and many built af­ter 2008) will have an ELCI. Older boats can be retro­fit­ted, which is highly rec­om­mended.

(GFEPs): Th­ese de­vices are for the ma­rina shorepower pedestal, not the boat, and serve the same pur­pose as an ELCI. With this de­vice on the dock, swim­mers are pro­tected from boats in the ma­rina that do not have an ELCI. With a thresh­old of 30mA, an ELCI or a GFEP will al­low enough cur­rent into the wa­ter that, ac­cord­ing to the chart, ap­pears to be enough to cause a fa­tal­ity. So what gives? For­tu­nately, a leak will dis­perse as it passes through the wa­ter, so swim­mers would not be ex­posed to the full cur­rent. For this rea­son, the NEC code al­lows up to 30 mA, leav­ing open the op­tion to in­stall more read­ily avail­able 5 mA de­vices. At 5 mA, how­ever, a dock­side pedestal will pro­vide far too many nui­sance trips to be work­able. The GFEP re­quire­ment for mari­nas ap­plies to new in­stal­la­tions only, and only in lo­cal­i­ties that have adopted the stan­dard.

white wires, in a per­fect world it would read zero be­cause the amount com­ing in through the black would equal the amount ex­it­ing through the white, as shown above (fig. 5).

If a fault oc­curs, say a chafed wire, then some amount of cur­rent will “leak” to ground. In that case, there would be an im­bal­ance be­tween the hot and the neu­tral. In the ex­am­ple be­low (fig. 6), the me­ter would read .030 amps, telling us that 30 mA are dis­ap­pear­ing some­where, pos­si­bly into the wa­ter. Re­mem­ber that .030 amps will trip the ELCI on the boat or the GFEP on the dock pedestal. All of th­ese ground fault pro­tec­tive de­vices work by look­ing for this im­bal­ance be­tween the black/hot and white/neu­tral cir­cuits. When that im­bal­ance reaches the thresh­old, the de­vice trips, break­ing the cir­cuit (as shown in fig. 6):

One crit­i­cal fi­nal point be­fore we shift gears out of the­ory and into so­lu­tions: neu­tral wires and the ground­ing wires are con­nected, but on­board your boat, they must be kept iso­lated. If the white/neu­tral and green/ground­ing wires con­nect on the boat, it be­comes pos­si­ble for the green wire to be­come en­er­gized. Re­mem­ber, cur­rent will re­turn to ground by all avail­able paths. By con­nect­ing the neu­tral to the ground­ing wire, you cre­ate a new par­al­lel path to ground. As we showed early on, that green wire is con­nected to the outer case of all 110 VAC equip­ment and to all of your underwater hard­ware. Con­nect­ing the neu­tral and ground­ing wires on­board cre­ates two po­ten­tially fa­tal haz­ards: elec­tri­cal shock on­board and ESD in the wa­ter.

an­other 5 mA and now the group to­tal crosses the line and ev­ery­one loses power.

If the am­me­ter test re­veals a 30 mA im­bal­ance on your boat, keep in mind that might be the cu­mu­la­tive to­tal from a num­ber of mi­nor is­sues on your boat. You might have one de­vice con­tribut­ing 10 mA, an­other adding 15 mA, and a third con­tribut­ing an­other 12 mA. Elim­i­nat­ing any one of the three will put you be­low the thresh­old that trips the pedestal.

This leads to the ques­tion, “How low is low enough?” Ac­cord­ing to a 2008 re­port from the U.S. Coast Guard, at 30 mA “… there should be no dan­ger to any­one who may be in the wa­ter around a boat.” The an­swer comes in two parts. From a safety per­spec­tive, un­der 30 mA will do, but if you want to be sure, you can plug in at any ma­rina, in­clud­ing the ones opt­ing for 5 mA pedestals, then you have to get be­low a 5 mA to­tal with ev­ery­thing run­ning.

In our boat­yards, we set up a por­ta­ble ground fault de­vice. We place this de­vice at the main dis­tri­bu­tion panel by run­ning one shorepower cord into the boat and into our test de­vice, and then an­other shorepower cord to com­plete the con­nec­tion to shore. Any cir­cuit with an im­bal­ance ex­ceed­ing the tar­geted thresh­old will im­me­di­ately trip our test equip­ment. At that point, the faulty cir­cuit has been iden­ti­fied, but the di­rect cause within that cir­cuit still must be de­ter­mined. The next steps re­quire a per­son with thor­ough knowl­edge of ma­rine elec­tri­cal sys­tems, a mind like Sher­lock Holmes, the tenac­ity of a blood­hound, and highly skilled in the use of a mul­ti­me­ter. of po­ten­tial prob­lems. If the in­dus­try pre­sented an award for the de­vice most likely to be im­prop­erly in­stalled, in­vert­ers would win and there wouldn’t be a sec­ond place. First and fore­most, the in­verter must be ma­rine rated. Ear­lier we talked about the need to con­nect the neu­tral and ground­ing wires at the source of power, but not on the boat. In­vert­ers (gen­er­a­tors and iso­la­tion trans­form­ers) be­come the source of power when pro­duc­ing AC power from the bat­ter­ies and must have a neu­tral-to-ground con­nec­tion.

In­vert­ers must have a way to make that con­nec­tion when in use and to dis­con­nect it when shorepower is present. The in­verter senses the pres­ence of shorepower and then goes through a syn­chro­niza­tion process that switches over to shorepower and breaks the neu­tral-to-ground con­nec­tion. Some AC cir­cuits might be in use dur­ing this switch­ing process, and that can cause a mo­men­tary shot of am­per­age from neu­tral to ground, trip­ping the ground fault de­vice. If this prob­lem oc­curs on your boat, try turn­ing off all AC loads when plug­ging in (you should do this step re­gard­less), al­low the in­verter a full minute to go through its switch­ing se­quence, and then turn the loads on.

Elec­tric wa­ter heaters can cre­ate leaks as the in­su­la­tion on the el­e­ment breaks down. AC cur­rent leaks into the wa­ter and to the case of the heater and finds its way into the ground­ing cir­cuit. Ex­te­rior leaks can also cre­ate prob­lems as mois­ture or cor­ro­sion on the elec­tri­cal con­nec­tions cre­ates a path to ground.

Air con­di­tion­ing com­pres­sors con­tain in­su­lated elec­tri­cal wind­ings. Over time the in­su­la­tion breaks down and can lead to elec­tri­cal leaks. If turn­ing the air con­di­tion­ing on trips the ground fault de­vice, you might need a new com­pres­sor.

Shorepower cords and shorepower in­lets can suf­fer from ex­po­sure to salt wa­ter. Cor­ro­sion can build up, pro­vid­ing a path for leaks be­tween neu­tral and ground. In­spect the ends of the cords the re­cep­ta­cle/in­let for green crusty buildup, dis­col­oration from ex­ces­sive heat, and pit­ting from arc­ing.

In­cor­rect wiring by un­trained tech­ni­cians or boat own­ers of­ten leads to neu­tral-to-ground con­nec­tions. Af­ter­mar­ket prod­ucts that are not in­tended for ma­rine use and/or are im­prop­erly in­stalled can lead to trou­ble.

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