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If
you've owned a boat for any length of time, you probably know that
insurance companies hire independent marine surveyors to conduct
insurance surveys on the boats that they insure. One of the most
common problems that surveyors run across in doing these surveys
are electrical systems that have either been jury-rigged by the
owner, or an owner who hired Joe-the-Electrician down the street
because Joe's work is cheap. Joe is the guy who knows how to wire
a house and thinks that boats are no different. The house business
isn't so good, so he switched to boats.
By the time a boat gets a few years on it, the
amount of substandard and/or jury-rigged wiring on it can add up
to substantial numbers of faults. Much to the consternation of the
owner, when the insurance surveyor comes along, he ends up handing
the owner a long, and frequently costly, list of things that need
to be corrected. Even more seriously though, is what substandard
wiring can do to your overall system, not the least of which are
chronic battery drain, frequent system faults, or even causing electrolysis
and fires. In the last month alone, I caught two boats that were
about to go up in flames, and one that actually did catch fire during
the course of a survey. One because the owner had installed air
conditioning controls below a companionway hatch that got wet and
shorted out, the other due to an improperly wired service outlet.
Let's begin with the fact that a boat is not a
house or a car, simply because the later two don't float in water,
which is what makes a boat inherently different. Especially a boat
that floats in sea water because sea water is a fair conductor of
electricity. Therefore, there are lots of additional rules
about the materials and methods of installation that you won't find
on land based vehicles or structures. Because water (both inside
and outside the boat) provides a very convenient ground path for
electricity, we have to be a lot more careful how we do things.
Marine Electricians There
are no schools for boat electricians, only ship electrical engineers,
except for the occasional vocational school. Most marine electricians
are basically self-educated by means of attending seminars and the
like. When hiring an electrician, you should not take their word
for it because it says so in the ad, or your friend said Joe was
really cheap. The least you can do is ask for a resume, since long
experience is probably the best criteria.
Materials & Equipment It
is important that only equipment and materials rated for marine
application should be used. The American Boat and Yacht Council
(ABYC) has very stringent standards for this, as does Underwriter's
Laboratories. This means things like common wire and wiring
devices, as well as electrical equipment, should not be used. That
non-marine fan, airconditioner or battery charger, because the electrical
apparatus is not properly constructed, insulated or grounded could
either start a fire, or worse, result in an electrocution. Federal
regulations require that all electrical devices used in the engine
compartment or bilges be "ignition protected" meaning
they won't create sparks that can cause a fire or explosion.
One of the worst offenses we see on boats is the
use of extension cords and other non marine wire, even such things
as audio speaker wire and household lamp cord on high voltage
systems. No, I'm not kidding. speaker wire carrying 125 volts. You
should never use household wiring devices, such as multiple outlet
expanders, or wire. Purchase electrical supplies only from a reputable
marine supplier. Wire must have the proper temperature, water and
oil resistant ratings and is hard to come by at retail outlets.
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| This service outlet was
replaced by some one who didn't understand high voltage wiring
and this is the result. The breaker was very old and
the contacts fused closed and would no longer trip.
This photo was taken during a survey while the wood behind
the panel was burning. The owner showed no concern about
it, thought it wasn't serious. |
Here's a good reason why
this ribbed plastic conduit should not be used on boats. Not
only is it highly flammable, but it spreads the fire. |
High Voltage Systems
No one who is not trained in marine high voltage
systems should ever perform wiring on a boat. The potential for
creating deadly system faults that are injurious to both people
and the vessel itself is too risky. That includes something as apparently
simple as wiring a new service outlet, for if you don't understand
the principles of the system, you are likely to unknowingly create
a problem. Just because you know how to do wiring around the house,
doesn't mean you know what you're doing on a boat.
Grounds and Grounding One
of the least understood aspects of a boats electrical system, and
the most troublesome, is the proper method of grounding. That
we often get questions of whether AC or DC electrical equipment
should be grounded to the boat's bonding system is illustrative
of this point. AC and DC grounding systems are two separate systems,
for distinctly different reasons. If you don't understand these
systems, you run the distinct risk of creating a disaster. Actually,
there are four separate ground systems: DC ground, AC ground, AC
grounding (or bond), and the vessel's bonding system. You can add
to this lightning and HF radio grounds as well. Do you know the
principles of each? Are you sufficiently confused to discourage
you from doing your own wiring? I hope so. For unless you understand
each thoroughly, you're headed for trouble.
The AC ground and grounding systems are "free
floating," meaning that they do not ground on the vessel, but
only to shore. The ground, or neutral, is a current carrying conductor,
and is the source of many troubles because people do not regard
it as such. The grounding, bond or green wire is the "safety"
intended to channel current safely to ground in the event of a short
circuit. Both of these circuits are capable of conducting current
and can be the source of electrolysis when there are system faults
with the dock or marina wiring. This is very easy to test for.
There is only one point where the DC side is grounded,
and that is at the battery. It, too, is a "free floating"
system in which nothing is ever grounded to any metallic part of
the vessel, most especially not the bonding system. Just like a
car sitting on rubber tires, completely insulated from earth potential,
the battery itself provides the negative potential.
The bonding system, also green wire, has nothing
to do with electrical systems. Underwater metals are simply wired
together to equalize differences in potential of different kinds
of metal. Nothing should ever be grounded to the bonding system.
Unfortunately, some people don't understand this and use it to ground
electrical equipment, occasionally with disastrous results.
Bonding Systems Bonding simply
means wiring all the boats underwater metals together. This is done
because of the galvanism caused by the different metals. By wiring
them together, the differing potentials are equalized. Bonding does
not solve problems of galvanism or electrolysis, but it does spread
the the flow of current around over more metal, so that 1/4 volt
or so won't cause any damage. Whereas if that 1/4 volt were going
to one small seacock, it would probably eat it up in a hurry. In
other words, bonding lessens the effect of small amounts of current.
On the other hand, it also spreads it around to all underwater metals
so that higher currents end up damaging everything.
Bonding systems use wire and ordinary crimped ring
terminals. After a while these get wet and corroded. Electricity
doesn't flow very well through corroded metal, so your bonding system
after a while stops working. To maintain it, simply cut off the
old terminals and install new ones. Do you have wires attached to
sea cocks with hose clamps? Forget it. This is putting stainless
and copper together, which are galvanically incompatible and it
won't work.
Your Bottom Paint What does
bottom paint have to do with electrical systems? Nowadays, with
copper based paints, a lot. If, the next time your boat is hauled
and you see large ugly burn patterns around all your underwater
metals, you got a stray current problem. Copper-based bottom paints
react severely to stray current, and serves as a great indicator.
Sort of litmus paper for electrical problems.
Of course, the common wisdom is that the stray
current "is from the marina." Or it's always the other
guy's boat that is causing your problem. Don't bet on it. Most stray
current problems are sourced on the boat in which they appear. Otherwise,
everybody in the marina would have the same problem.
Electrolysis and Galvanism Electrolysis
is a word that is badly abused by boaters who don't really know
what it means, so let me correct this right now. First, understand
that all boats have an electrical potential. That's because of all
the different metals on the boat which, themselves have differing
electrical potentials. This is exactly the same principle that makes
a dry cell battery generate electricity. This electrical potential
is called galvanism and is the reason why we put
zincs on boats.
Electrolysis is stray current escaping
from the system and is most damaging. It is an abnormal condition.
When this happens, it will eat up the zincs in no time, usually
leaving that metal looking bright and shiny. Therefore: Shiny zincs
= electrolysis. Dull eroded zincs = galvanism.
I spent two years putting a meter on every boat
that was hauled for survey. The average boat generates about 1/4
volt DC current and going as high as 1/3 volt without causing damage.
But when it gets up to 1/2 volt, you got a problem. Zincs will erode
rapidly and underwater metals begin to be affected.
Shore Power Cords The single
largest cause of problems with shore power systems results from
failure to maintain the connectors on both the cord and the boat
connectors. These devices are exposed to water and over time suffer
from corrosion and general wear. High resistance caused by corroded,
bent or worn connectors results in high resistance which causes
overheating, which further amplifies the power drop. This not only
creates conditions for a potential fire, but causes electrical equipment
to work harder, resulting in reduced life span of equipment. IT
PAYS TO MAINTAIN SHORE POWER CONNECTIONS.
You can perform a very simple check just by placing
your hand on the shore cord near the connection to determine if
it is heating up. Obviously, this should be done while you have
a lot of equipment turned on. If it's anything but slightly warm,
not more than 110 degrees, suspect a problem. Shore power
connectors should be dismantled at least once per year, cleaned
and repaired as necessary. Most of these connectors have replaceable
parts. If you drop your shorepower connector in the water, you must
take it apart, clean and dry it. Otherwise, expect it to burn up.
We recommend that you buy only the highest quality
power cords, as these will last longer and have the advantage of
replaceable connector parts. Cheap connectors usually can't be taken
apart. We also advise against ever using the three-pronger household
type adapters as this type of connector is highly unreliable
and prone to causing system faults and fires. Only the twist-lock
type connector is suitable.
One more thing: If you are not turning off the
dock breaker before disconnecting the power cord, start doing it
now. Not only do you risk getting electrocuted, but disconnecting
an energized connector damages the contacts. Also consider what
happens if you drop the energized cord in the drink!
Polarity This is an issue
only with 125 VAC systems since 250 VAC systems will not function
with wrong polarity. Since you have three terminals on a shore connection,
wrong polarity can mean that any of these wires are in the wrong
position. Not only should you pay attention to the polarity indicator
on your boat, we recommend that you keep a plug in polarity indicator
aboard and use it every time you hook up to shore power at a different
location.
Reverse polarity is not only an electrocution hazard,
but can also damage electrical equipment. It is most often found
with the three prong spade connectors (household type), but occasionally
twist lock connectors as well, particularly in marinas with dilapidated
equipment. Never trust the power supply at strange docks, but always
check the polarity. When hooking up to strange docks, always check
your volt meters to make sure you have adequate voltage. Low voltage
is very damaging to electrical equipment. Turn on the stove or water
heater and watch what happens to the meter.
Main Circuit Protection Many
people think that the circuit breakers on the dock protect their
boat. They do not; they only protect the dock wiring. Your main
circuit breaker protects your boat's systems. But what about that
section of wiring and connectors between your main panel and the
dock breaker? Well, the fact is that it is unprotected. which is
why so many fires occur. Check out all the top end boats and you
will find that they have circuit protection located directly at
the shore connectors. Which is why we recommend that you should
too. Having slow blow cartridge fuses installed directly at the
connectors can go a long way toward preventing fires and burned
up shore cords, particularly if you are a traveler and frequently
rely on uncertain power supplies. Circuit breakers should NEVER
be installed on the exterior of the boat. Only gasketed, water proof
cartridge holders should be used.
Circuit Breakers Circuit breakers
wear out, and when they do they work less well, or not at all. If
you are using circuit breakers as ON/OFF switches, you are helping
them wear out that much faster. It also damages breakers when you
shut off equipment via the breaker. This causes arcing at the contact
points which damages the points. When connecting and disconnecting
shore power, you should always turn OFF equipment at the appropriate
switch on the equipment. Then shut the main breaker off. Do not
ever simply throw the main breaker off to shut down equipment that
is operating. The circuit breaker arcs and damages it.
Also be aware that any equipment run by a motor,
such as air conditioning and refrigeration equipment, start up with
an initially much higher amperage than the normal running amperage.
An air conditioner that runs at 14 amps may have a start up amperage
of 20 amps, so that if you just go and turn all the equipment on
at once, it overloads the system. Then the circuit breaker gets
hot and won't stay engaged until it cools down. Ergo, start up heavy
equipment one item at a time, allowing it time to cycle into its
normal operating voltage before turning something else on. For example,
don't turn the AC, refrigerator and icemaker all on at once and
not expect the breaker to pop.
Chronic Breaker Popping
It's human nature that when a problem appears, we wish it to go
away. Breakers that pop frequently are signaling that there is a
problem, which could either be the breaker, or something in the
circuit. Yet most people will keep on attempting to make the breaker
engage. This can be dangerous because you may cause the contact
points of the breaker to fuse together from arcing, in which case
it will never trip again. The above photo shows what can happen
when you do this. DO NOT ATTEMPT TO ENGAGE A BREAKER THAT IS OVERHEATED
BY FORCING IT. You must allow it to cool down.
If you are experiencing chronic problems with circuit
breakers popping, first check how much current draw is involved.
A single 30 amp circuit is not much when you're running things like
air conditioners, water heaters and battery chargers. One very simple
way to check whether you're dealing with an overload problem is
to add up the amperage draw of each piece of equipment. List both
the start up and run amperages. You will usually find the amperage
given right on the equipment label. By making a list of the
total power demand, you'll get a good idea of what you can and cannot
operate simultaneously, particularly when starting the equipment.
If you have an ammeter on your panel, check it against the amperage
tally you made. Ideally, you should try to hold power consumption
at 80% or less than the line rating.
Check the breaker by allowing it one hour (or whatever
it takes) to cool down. Turn the equipment off and, after
it is cool, reengage the breaker. Now turn the equipment back on.
Place your finger on the front of the breaker and note its temperature.
If it does not heat back up again, then the problem was probably
a start-up overload. If the temperature rises again, there is a
fault in the circuit or the breaker. (Note: when the breaker contact
points become eroded, the breaker itself can overheat).
GFCI's Ground fault current
interrupter service outlets are required to be installed in wet
locations such as the galley or head. In reality, there's little
chance of being electrocuted inside a boat because you are not grounded
within the boat. A greater risk is from service outlets being located
in places that get wet, such as below leaking windows, hatches or
close to doors. Three pronged plugs are prone to shorting across
the terminals when wet, so having all your service outlets changed
to GFCI's is a good idea. Use only the highest quality devices from
a reliable manufacturer like GE, and not the el cheapos from the
local discount store. They aren't worth having. Service outlets
located anywhere on the exterior of the vessel are an invitation
to trouble for reasons that should be obvious.
DC Systems
The same advice about jury-rigging wiring applies
to DC systems as well AC systems. While you're not going to create
an electrocution hazard, it is very easy to take a faultless system
and create faults in it. A typical problem starts like this:
The owner wants to add a new piece of equipment, but the electric
panel is way over there, and the place he wants to install the equipment
is way over here. Besides, there are no extra breakers in the panel,
and no space in the panel to add another one. To make matters worse,
the panel is located in such a way that he couldn't string new wires
into it even if he wanted to. So what he does is to find a place
where he can tap off an existing circuit, and maybe adds an in-line
fuse, stringing wires all over the place in the process. Or maybe
he is replacing a piece of equipment that has a faulty circuit,
but instead of trying to locate the fault, he just clips off the
old wires and strings new ones. This happens a lot, and by the time
the boat has a few years on it, it's got cut wires all over the
place, many of which are still hot!
In many cases, he will just go and take new leads
off the batteries, bypassing the panel altogether. Now when he goes
to turn off the main power supply, all that new stuff added remains
energized. In addition to which in-line fuses have also been added
all over the place, so when something craps out he's got to go tearing
through the boat to find that hidden fuse.
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If you have electrical problems and
your system looks something like this, then you needn't look
much farther for the source of the problem. |
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Not every electrical system is going
to be this neat, but this is the way it should be. |
The worst of the problems with DC system add-ons
comes with improperly installed wiring and the use of wire splices
of all sorts. Typical of these are the use of electrical taped connections
which, when the tape gets warm (as in the engine room) the tape
glue gets soft and the tape falls off. Or the use of wire nuts or
crimped butt connectors in locations that get wet. Wire nuts (those
twist-on cones) are not approved for marine use. When connections
get wet, the wire corrodes, creates high resistance, usually resulting
in equipment damage or failure for reasons which the owner will
never discover. He'll think just that damned lousy piece of equipment
crapped out, when in fact the lousy wiring job is the culprit.
Principles of Wiring I would
venture to say that half the electrical problems on boats result
from improperly installed wiring. After the boat is built, there's
no convenient way to route new wiring. But we need to understand
that systems on boats are subject to high G-forces due to pounding,
rolling and vibration. Connections get stressed and wires rub and
chafe against abrasive or sharp objects. It doesn't take much damage
to wire insulation before you have a condition where stray current
may develop. And the chance of finding a little bit of damage on
one wire is about nil.
1. Must be routed in a suitable,
dry area and be well secured. Should not be laying in bilge or in
areas that get wet.
2. Must not be routed with pipes
or hoses of any kind, and not be in contact with fuel tanks or fuel
lines.
3. Splicing circuits should be
avoided. If splicing is necessary, it should employ a proper terminal
block, and not butt connectors (see above photo). Every splice in
a circuit creates additional resistance, and the potential for the
connection to come apart. Taped connections and wire nuts should
not be used.
4. Wiring must be firmly secured
and in locations where it won't get damaged. Should not be dangling
or strung across open spaces. Use only plastic, not metal, clips
to secure the wiring.
5. Must have chafing protection
or conduit at vibration points around machinery.
6. Must not be in contact with,
or proximity to machinery exhaust systems.
7. Wiring should be neat. A boat
full of tangled wiring demonstrates unprofessionalism and the inability
to fix something that goes wrong. An electrician can't trace a plate
of spaghetti, and when something does go wrong, the cost of fixing
it goes way up.
Circuit Protection Adding
in-line fuses to a newly installed piece of equipment is a terrible
way to add circuit protection. First of all, these devices trap
water and corrode internally. Secondly, you end up with two more
splices in a wire circuit that shouldn't have any. Third, you usually
forget where they're located, and if you've got ten of them on your
boat . . . well, you get the picture. Jury-rigged systems are just
that; a temporary, unreliable system. A boat full of in-line fuses
is a boat full of short cuts and amateur installations.
Batteries Batteries are a constant
source of aggravation to many boat owners, almost always for reasons
that are preventable. These are: low quality batteries, poor or
non existent maintenance, and improper installation and wiring.
As a general rule, batteries perform consistent
with the price you pay for them. Good batteries are expensive, and
shopping for price will only lead to momentary satisfaction. Cheap
batteries have thin plates and poorly insulated casings and therefore
cannot give long service.
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| This illustrates why crimp-on ring
terminals, wing nuts and other substandard high amperage cable
connectors should never be used. High resistance has melted
the cable insulation and burned up a $900 starting motor because
of high resistance. |
Secondly, batteries have to be installed correctly.
That means in a clean, dry location that can be reached. If you
can't reach them, if you have to kill yourself to get at them, then
you will not maintain them. If installed in an inaccessible location,
you should consider having them moved to a better location.
Place a fully charged battery on the concrete floor
of your garage. Then come back two weeks later and check the charge.
That battery will have completely discharged, and it will have done
so right through the plastic casing. Now you understand my point
about proper installation and dryness. On many small boats, I usually
find the batteries sitting in uncovered plastic boxes that are full
of water. Or they're sitting in bilge water or on wet decks. If
that's the case, you needn't look any farther for at least part
of your problem. If you want your batteries to be reliable, they
must be kept clean and dry. That includes the top surface, particularly
between the terminals.
Proper Lugs It won't do
to make your cable connections with threaded studs and wing nuts.
These afford inadequate contact surface that can cause high resistance
and is one of the major causes of engine starting motors burning
out. Your starting motor cables should be attached only with swaged
lead lugs, not the ring terminal kind smashed with a hammer to make
the connection. Small boats are usually the worst offenders in this
regard.
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| Corrosion takes
its toll even on the interior of the boat due to leaks, salt
air and high humidity. When tested, most of these connections
had high resistance. This is the proper method to splice wires. |
Ventilation Batteries develop
heat when charging, as well as hydrogen gas. For that reason, the
need to be in a well ventilated area. Gel cells are particularly
vulnerable to overheating damage. Putting gel cells in covered,
plastic boxes has proved to be a problem, and for this reason they
are falling out of favor. Sometimes improved technology isn't an
improvement after all.
Electrical Devices Exposed to Weather Why
it is that there so many builders that install instruments, panels
and switches in locations that are going to get wet is something
I'll never understand. Oh, I know, you look at those switches and
think that they're water proof. Well, you just go look at the back
side of the panel and see if you still think so. See if you don't
see a lot of corrosion back there. What happens when the back side
gets wet? Well, water being a conductor means that these devices
will short small amounts of current across the terminals, or to
any available ground. This is one of the reasons why you have so
many engine instrument failures, and boats have so much of
a hardware corrosion problem, and why they have stray current problems,
never mind equipment failures. Electrical equipment exposed to weather
that is not absolutely water proof is just asking for trouble.
Locating Internal Equipment
Just because it's inside the boat doesn't mean that electrical equipment
will stay dry. Boats leak, and stuff located under those leaks are
going to get wet. That means that you have to pay attention to where
you put stuff. Many people mount various types of pumps low in the
bilge, assuming that the bilge water is never going to rise. Believe
me, the bottom of the boat is the last place you ever want to mount
something. Sooner or later your bilge pump will fail, and when it
does that expensive equipment is going to get ruined.
The other place you never want to mount anything
is under an open cockpit deck. For reasons I won't get into here,
this is a terribly wet environment, which is why boats with generators
located here end up replacing generators a lot.
If you have exposed panels you need to keep them
covered and dry. The vast majority of small boats that I see don't
even have panel covers, yet alone having covers that are used. Having
a small cover made up is a small price to pay to avoid serious damage
and other problems.
|
Looking at this ball
of wiring hanging down, is it any wonder that a lot of electrical
equipment on this boat didn't work? Instrument panel of
this open boat was not kept covered. Water pouring through
the panel had even filled up the battery boxes with water. |
| 
|
Close up of wire bundle
above. These supposedly water proof wire connectors, on closer
examination, are found to be full of water. |
Engine Wiring Due to vibration
and high temperatures, damaged wiring on and around engines is one
of the most common causes of stray current damage, i.e. true electrolysis.
It is extremely important to consider the routing of the wiring
so that it is not in contact with hot manifolds, or vibrating on
sharp edges or rough surfaces. Engine wiring should be inspected
periodically for signs of damage.
Avoid using the kind of highly flammable plastic
conduit shown above. If you are painting the engine, do not paint
the wires; the solvents in the paint causes the insulation to become
brittle and crack.
The Effects of Time Electrical
systems don't last forever. Over time boat systems degrade, particular
as respects to the effects of corrosion. We recommend that a boat
should have an electrical system survey once every 5 years. This
does not take long and does not cost much, and can save you thousands
of dollars in unwelcome headaches. In most cases, the survey will
simply reveal the effects of corrosion which needs to be cleaned
up, along with few possible minor repairs. The advantage is in not
allowing problems to accumulate to the point that it becomes a big,
costly job.
A Word About Buying Older Boats Everything
I've said so far comes to bear on what you are likely to obtain
when you buy an older boat. One of the things that we pay close
attention to in performing a survey on a used boat is how much jury-rigging
and alterations there are in the electrical system. Sometimes there's
a lot, and if the new owner isn't willing to foot the bill to make
corrections, more often than not he's going to be living with a
lot of electrical headaches. In most cases, he's not even aware
of why things are constantly breaking down; he just knows that things
unexpectedly keep crapping out. Usually he blames the pump or motor,
or whatever gizmo that fails, when actually faulty wiring is the
problem. Beware that on boats with bastardized electrical systems,
the cost of straightening it out and cleaning it up can be pretty
high.
Adding New Equipment
Most boats, particularly smaller ones, are unfortunately
not designed with the idea of adding equipment, even though nearly
everyone does. But the primary reason why systems gets so
messed up results from the attempt to force something in where there
is no provision for it.
The best way to deal with this is to simply add
a new panel, whether AC or DC. Doing this is neither very difficult
nor expensive, especially considering the cost to repair all the
problems you're likely to create when you try to cram something
onto a system not designed to handle it. A six breaker DC panel
will cost less than $200 and is a whole lot better than scattering
inline fuses all over the place, and with installation will run
less than $500. Plus, the new panel can be added at any location
where it will be convenient.
Adding a second shore power circuit is especially
useful for those boats with single 30 amp shorelines where the addition
of new equipment will tax the system. It's not very convenient to
have to turn the water heater off to turn the air conditioning on,
or constantly be managing equipment as breakers keep popping off.
You have two options here, the first of which is to increase your
shoreline to 50 amps. To do that you have to change the main breaker,
power receptacle and the shore cord, which is a lot bigger and heavier.
The other option is to add a second 30 amp circuit, which means
adding a new panel, receptacle and shore cord, which costs a bit
more.
Adding a second circuit has the advantage of separating
the air conditioning onto a separate line, which is the way all
good systems are designed. That's because of the high power demand,
combined with frequent dock power faults, makes it desirable to
separate it from the main service.
Multiplex Systems A multiplex
system is a multiple power source system which permits switching
from one line to another, from one power source to another. For
travelers, this is extremely useful to deal with unreliable dock
power, or sudden faults in your own system. It allows you to choose
which line you want to run equipment on, and particularly if you
have a generator, it provides a great deal of flexibility.
Let's say a circuit breaker on the dock goes out while you're cooking
dinner and it's very hot this day. Instead of only being able to
turn the AC off and go on cooking in the heat, you can fire up the
generator to run the failed circuit simply by switching it over.
The better larger boats invariably have this kind of system.
The reason why low cost boats don't have this kind
of system is because it requires the use of very expensive rotary
switches that costs $300 - $600, plus some more complex wiring.
But it is an extremely good system to have. See photo below.
 |
As versatile as it can get. This boat
has (2) 125 and (1) 250 shorelines plus generator for a total
of 4 power sources. These are controlled by the six rotary
switches, each with four positions, so that any combination
of power sources on any branch circuit can be selected. |
Posted July 14, 1998.
Revised and added two pictures November 02, 1998
|
