[Public-list] Shore Power on the cheap.

Meinhold, Michael J MICHAEL.J.MEINHOLD at saic.com
Thu Feb 24 09:25:11 PST 2005

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.


-----Original Message-----
From: public-list-bounces at alberg30.org
[mailto:public-list-bounces at alberg30.org]On Behalf Of Don Campbell
Sent: Thursday, February 24, 2005 12:02 PM
To: Alberg 30 Public List -- open to all
Subject: Re: [Public-list] Shore Power on the cheap.

    Shore power on the cheap is only as good and as safe as the weakest
link. Good shore power is not that expensive for the safety it provides.
First read the fine print of your mooring agreement to know what your
liability is for both you and your marina or  yacht club in
the case of damage to facilities. Second check with your insurer to make
sure you have insurance coverage for your boat and any liability for  loss
to mooring facililties and other hulls if there is a fire that can be traced
to your electrical  system. (If you have a 15 amp
cord from a 30 amp connection, without a 15 amp fuse at the start of the
cord, then 30 amps may be driven down it to the fuse. If the cord shorts due
to heat, then you will have a fire.) If you need ABYC standards for
insurance, then be sure your cheap system has those
standards, particularly in the US where you have such a litigeous society.
(And there are some out there who wonder why insurance has gone up so much
    The operative thought here should be that you want at least the same
safety and care on the boat that you would have at home and probably in the
bathroom or kitchen since that is where water and electicity meet in the
home.  At home you have a main breaker and circuits
downstream from there. Any wire  to the main breaker  is capable of
conducting that load as fed from your power supplier. Any total usage above
the main breaker will trip the system. Any wire from the main breaker fed to
the panel will be capable of handling the load from
the main breaker to the individual circuit breakers. Wireaway from  the
panel circuit breakers will be sized according to load, in most cases 14
guage, but certainly much bigger than that for electric furnaces, dryers,
and ovens. There may also be restrictions for kitchen
appliances so that one plug outlet is on its own circuit in what is known as
a split receptical,so top and bottom plugs in one box have 2 circuits.  In
Canada, we cannot have a duplex in a bathroom that is not a GFI unit.
    For the  shore power that you are talking about, you need a proper
connector on the hull  with threaded ring so that a proper, waterproof
electrical cord may be securely attached to the boat. Non-metalic boat inlet
plugs with covers  for 30 amp power are less than $50.
You then need to have a 30 amp fuse or breaker on the incoming line,  so at
least a 3 circuit panel is needed. On two circuits you can put the main
incoming line with a 30 amp breaker. and take the power off this to the
other circuit with a 15 amp breaker or fuse. Then you
need a junction box capable of holding a GFI duplex. You are then able to
use the 15 amp circuit for this duplex. From here you may then use your 15
amp cord. The only other thing you need is the shore  power cord. For a safe
acceptable fix for everything, you will be in the
neighbourhood of  $200 and within standards. See Nigel Calder's book on
maintenance and electrical information for more on how to do it if you still
have questions.
    I really have a concern with farmer's fixes with electricity near water,
when you can do it safely for so little extra effort and $. Stray voltage in
the water, is capable of killing any swimmers too.One problem is lack of
availability of waterproof cords and connectors
as 15 amp units. The other thing to note is that you should make sure you
have at least 14 guage wire in your  15 amp cord. There are so many out
there that are 16 guage and they are not good for high load ( tools and
kettles) or continuous usage (battery chargers).
    If you really feel you can take the risk for the worst loss imaginiable,
and  go with a cheap system, install a ground fault interrupter at the 30
amp plug at the box if it is not already there and a waterproof fuseholder
with a 15 amp fuse in line at the box with that.
Then all that will happen if things do draw too much current is your battery
won't charge.
Don #528

dan walker wrote:

> mike,
> ignorance is bliss. i did that for three years in charleston. marina folks
had no problem with it. of course they could have been ignorant as well. the
boat sat unattended for up to three months with no problems. of course
during the three years there were no hurricanes.
> dan
> "Meinhold, Michael J" <MICHAEL.J.MEINHOLD at saic.com> wrote:
> I don't really want (and can't afford) a complete, safe shore power system
> for Rinn Duin. I would, however, like to occasionally use power tools at
> dock, and occasionlly run a battery charger or a fan. I do not intend to
> ever run an airconditioner or microwave or an oven.
> Is there anything wrong or unsafe if I get a 30 amp to 15 amp converter
> attached to the dock connector, plug in a 15 amp-rated extension cord, and
> plug into that a 4 or 6 outlet power strip with a 15 amp circuit breaker.
> I also can find an in-line Ground Fault Interrupter, wouldn't this be as
> safe as an installed shore power circuit? Should I have any concerns about
> leaving this unattended if properly secure the line?
> Mike
> Rinn Duin #272
> Michael J. Meinhold / Senior Engineer / SAIC
> 2111 Eisenhower Avenue, Suite 303 / Alexandria, VA 22314-4679
> PHONE : (703) 842-2606 FAX: (703) 842-2617 EMAIL :
> michael.j.meinhold at saic.com
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