"Rusty O" wrote in message
hlink.net...
There are some simple rules to follow. The only problem is they may be
difficult to implement in some cases.

Rule #1 For safety reasons, all AC systems need to have the neutral and
ground tied together.

Rule #2 The neutral and ground must be tied together at ONLY one place.

Rule #3 If you are connected to shore power, without an isolation
transformer in your vessel, the neutral and ground will be tied together
at
the shore-side service panel.

Rule #4 If you are connected to shore power, as in rule 3, you MUST NOT
have the neutral and ground connected together aboard your vessel.

Rule #5 If you have an AC generator, of any voltage, the neutral and
ground
should be connected together at the generator.

Rule #6 If you have a true isolation transformer on board with the shore
power connected to the input and the output feeding the loads on your
vessel, then you have created a 'separately derived system'. In this case,
you would connect the neutral output of the transformer to the vessel
ground
to satisfy Rule #1.

Snipped the rest of this wonderful material . . .

Brilliant, Rusty. The most concise presentation of AC grounding I've seen.
Many thanks.

--
Jim B, Yacht RAPAZ,
Sadly, for sale:
http://homepage.ntlworld.com/jim.bae...cification.htm
jim[dot]baerselman[at]ntlworld[dot]com

Rusty,

Thanks very much - and I think I've sorted out my confusion. The
books are written from a US perspective and they are talking about the
US 4 wire system - 2 hot wires, a neutral at 0v and ground. So it
makes sense to ground the neutral. When read from a UK perspective
with only a 3 wire system, then it makes no sense to ground the
neutral, which is a hot wire. I've since found an excellent web
search searching through this group which has some really usefull
wiring schematics - which also confirms that it is a real snakes'
wedding with 400v, 240v, 24v and 12v systems!!!

Colin

On Sun, 28 Dec 2003 01:13:43 GMT, "PeteAlbright"
wrote:

Many ships have ungrounded systems, with ground fault monitoring. Single
phase panels are used (without the neutral bus), or three phase panels (120
volt delta). All circuits use 2 pole breakers. Common ground monitor is
lights from phase to ground, if the light is out the phase is grounded.

Pete Albright,
Tampa, FL

Now that you mention it I do think I remember a light on our
knife-switch/screw-in fuse panel (black bakelite with wooden safety
leaning bar), that alerted you to any current to the deck, indicating
a fault.

The cal lab had a Detroit Diesel, naturally-aspirated 6-71 2-stroke
diesel driving a DC generator that originally powered the stern gun
mount and director, which was removed when the disasterous DASH
anti-sub helicopter was installed. The DC powered a big
motor-alternator through a separate manual panel to create 60 Hz, 3
phase, 440 VAC that was fed to a bank of transformers buzzing away in
the cal lab to keep us awake at night. All our Edison Lights were run
directly from 110 VDC from the DC panel through a couple of knife
switches....as Edison intended.

The whole ship would go dark because of the Electical gang's
incompetence a few times per voyage. The separately-powered cal lab
shone like a beacon in the dark, then....(c;

Larry ET1
Shop 67B, Calibration Lab
USS Everglades (AD-24)
Charleston, SC (1966-1969)

Electricians were not allowed to have keys to OUR generator
room.....hee hee. They never gave us keys to THEIR generator rooms,
after all. It was only fair.

In the Med, we used to turn the motor speed on the alternator down and
run the cal lab on 50 Hz to keep the TV picture from pulsing at 10 Hz
from the differences in scan frequencies and power supply hum....(c;
I still have reel-to-reel tapes with 50 hz hum on them!