[Public-list] Shore Power on the cheap.

[Don Campbell]

Mike;
    Risk for money:
    There was a time when a 40 amp 20 circuit sevice was ample for a house.
Thirty years ago,  when I built my house, a 200 amp - 48 circuit panel was
considered capable of some expansion within the system. That worked fine until
we have upgraded the furnace to a geothermal one and now need a 200 amp-  60
circuit system and this house is not one that is totally wired for
communications as they now project.
    Anytime anyone wants to use only a partial amount of the energy supplied
does not change or  reduce the need for a safe system. You see that every day in
your home where you have a main breaker or fuse of a given size, and you do not
excede that amperage, so do not  trip the breaker. It is a system in which you
have a very limited say in the voltage or current supply since that is
dertermined by your energy supplier. You do have a choice of how you specify and
buy energy based on the comparable costs and volume used, - whether you need or
want 3 phase or single phase and the associated voltages. In all situations, the
power supplier will not allow you to buy energy until they inspect your system
to assure themslves you have done things to the accepted code of practice which
includes both wire size and circuit overload protection, the latter at the front
of the circuit not the rear.
    That you want to do the same on your boat and draw only a partial amount of
the energy that is provided is fine. However, the protection and safety of the
system should be based on the same principles (correct wire size and overload
protection to protect the wire in the system )  as your  land based energy
systems understanding  that water and electrical energy don't mix very well,  so
there is an added measure of safety needed to protect you (GFCIs). Circuit
breakers and fuses work at the level of amps,  GFCIs  work at the range of 2-4
milliamps.
You have choices that you can make.
1. Surveyors often comment on the shore power system, so you might start by
looking in your most recent survey. If nothing is specified, you might want to
contact him or her to see what they suggest from the ABYC standards,
particularly if you are needing a survey for insurance in the future.
2. Hire a qualified electrician to set up and wire  the system which is similar
to what you would do at home,  I presume.
3. Get and pay for professional engineering advice to design the system.
4. The last is to do it yourself, but to do so means that you take the risk and
liability, (regardless of what job you undertake or what you meant to say or
imply).
    The ABYC has done the electrical engineering (including specifying wire size
and connectors and UL safe equipment)  for you,  so that is a good place to
start. Your insurance company is also a player in the risk you take and may
specify that they will not cover your system unless it meets ABYC code, very
similar to the inspection  program in your home. (It does not matter whether
they inspect it before or after a fire, there is usually enough evidence
available after a fire to pinpoint electrical faults and then the result will be
clear if the code is not met.)
    As a further note, the covering used on the "waterproof" cords and
connectors is cheap when used in areas with  salt water which has a really nasty
effect on copper and household or non-marine cords.
    In my experience, most marinas charge a flat annual rate for a power hookup
and so what system you have to extract energy and how much you use is irrelavent
for determining operating costs.  The capital costs for a safe system are
relatively small if considered over a 5 or 10 year timespan, and will be far
less than the annual hook up you pay the marina or YC.
Don #528

"Meinhold, Michael J" wrote:

> Don -
>
>   Thanks for the analysis. I don't mean to imply that I am willing to trade
> risk for money. I am willing to trade unneeded capability for money if I
> can. I was asking if 15 amp service could be extracted from a 30 amp supply
> and end up cheaper. Based on what you wrote below  - it can't!
>
>   I will look at total cost, but I think it's a future project.
>
> Mike


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