So you're saying not to ground the AC ground at the boat, but to rely on the
shore ground? Everything I've read says you must ground it at the boat as
a safety precaution against faulty grounding at the dock. Did I
misunderstand something?

I can't (conveniently) isolate my house DC from ground since I have a
non-isolated ground alternator.

Don't SSB antennas need to be grounded? Do the radios isolate the antenna
ground from DC ground?


"Larry" wrote in message
...
"johnhh" wrote in
:

So are you complaining that the AC ground and DC negative are both
connected to the boats ground
"Boats ground"? What's that? The boat is made of PLASTIC, an insulator.
It has no "ground". It has a negative battery bus. It has an AC supply
ground connected to the shore power ground system. What's the "boats
ground"?

I hear this a lot. It doesn't exist. The battery negative bus has no
relationship, whatsoever, to the AC shore power ground as the two systems
are totally isolated from each other unless there is something wrong with
your battery charger, dual-voltage fridge or other AC/DC components.

Touching the AC shore grounded appliance, already hooked to AC shore
ground, with one hand and touching the engine block connected to the sea
and DC ground bus results in no hazard...unless the AC shore ground is
defective PLUS the appliance or device is defective. Touching an AC
grounded device with one hand and a defective 2-wire toaster with the hot
lead of the AC line hooked to its metal case has the SAME SHOCK as
touching the DC ground bus hooked to the engine block....unless, of
course, the boat has a proper GFI that should, but is not, required
aboard the boat....just like proper NEC-approved breaker panels are not.
(A bunch of little plastic breakers on a plastic panel screwed into a
flammable wooden box made of some exotic, expensive wood is NOT up to the
National Electric Code of the USA or any country with any brains. AC and
DC panels in boats are made that way to SAVE MANUFACTURERS MONEY. They
are NOT "safe", from fire (flammable) or explosion (not sealed against
fumes) at all!

Ok, back to the buses connected together for some stupid reason.....

If the DC bus hooked to the zincs by virtue of the DC bus being connected
to the engine block....is connected directly to the AC bus ground back to
shore power ground through the boat's impressive yellow shore cable, this
connects the boat's zincs STRAIGHT TO THE BOTTOM OF THE HARBOR...not to
mention every other boat wired this stupid way. YOUR zincs are hooked to
HIS underwater metal parts through the common-connected AC shore power
ground wires.

So? What happens now?........(you ask).....

Ever notice the metal conduit hanging loose under every dock on every
marina in the country? See how it hangs into the water? If I hook MY
zincs to that metal conduit (by the AC shore power ground wire from the
boat with the DC negative bus hooked to AC shore power ground), MY zinc
will fizz away protecting the rotting plating on that sagging conduit,
every little ground wire touching anything conductive hooked to the
water, and even the ground rod back at the feed point from the power
company! Isn't that nice of me?

Is it any wonder some people are going through those amazingly-expensive
zincs at an alarming rate in your marina? Zincs protect what they are
CONNECTED to. They are a virual shorted battery, the zinc one plate, any
metal part making connections with the water the other plate and seawater
as the electrolyte. In order for the battery to DISCHARGE, eating the
zinc, it has to have a DIRECT DC PATH from the zinc to that plate.
Unhook the path, you've opened the shorted battery circuit. The only
battery plate the UNHOOKED boat makes a battery with is the metal part
the zinc is mounted on and is protecting, not every neighboring boat
connected to the AC power shore ground.

Every AC device in the boat, with, of course, the exception of insulated,
UL-approved, appliances-electronics-doubleinsulated drills-etc....should
be hooked for safety to the SHORE GROUND, to prevent the AC line from
appearing on the metal cabinet parts of it. Of course, it would be nice
if the damned AC panel, ITSELF, on pleasure boats were so connected.
They're not. Look into the wooden box. Metal breaker panel hooked to
green wire? Not most.

If you disconnect the DC negative bus from the AC Shore Ground green
wire, you measure the DC potential caused by the zincs...the
electroplating voltage trying to destroy the zincs. It CAN'T have any AC
voltage between the Shore Ground hooked to a ground rod somewhere and the
DC ground bus hooked to the engine block....doesn't wash.

"johnhh" wrote in
:

So you're saying not to ground the AC ground at the boat, but to rely
on the shore ground? Everything I've read says you must ground it at
the boat as a safety precaution against faulty grounding at the dock.
Did I misunderstand something?



The boat is made of PLASTIC. You cannot ground the fiberglass. If you
have a steel hull, I still wouldn't connect the green wire to it. It is
already "grounded" through the seawater. You'd just add to your galvanic
action problem. You may not be able to isolate it as the grounded
equipment is hooked to the hull in lots of places, anyways. Fiberglass
boats are being discussed.
All AC grounds are to be connected to shore power "ground". This insures
you get knocked on your ass if you touch AC hot and the grounded fridge
case. But, that's the way they want it. Buy a plastic cased fridge,
problem solved. The battery charger should have its DC circuit isolated
from its AC circuit. If it's not, I wouldn't buy it. The + and -
charging terminals should be totally isolated from the power-line-
grounded case.

If you tie the "faulty ground" at the dock, let's say it's open from
corrosion or the wire is busted, connected or not to DC ground in the
boat...it's still open. If the plug is wired wrong, the AC box is still
grounded to ground. You'll get knocked on your ass plugging your
grounded plug in if it doesn't explode in your hand before the breaker
trips. Grounding the hot AC line through the faulty hot-connected-to-
green-wire-to-the-boat absurd scenario in the DC to AC interconnected
ground scenario only results in a big flash as the AC current has a
direct path to ground through the engine block/propshaft, tripping the
breaker I hope unless some other absurd scenario has it bypassed....

I'll be absurd, too. Every boater should have a ground detector built
right into the AC breaker panel!

Jeez Larry, I didn't say anything about grounding anything to a plastic
hull. I also did not say that the AC ground should not be grounded at the
shore side. I said that everything I have read says it should also be
grounded at the boat end. Just like that grounding rod outside my wood
house.


"Larry" wrote in message
...
"johnhh" wrote in
:

So you're saying not to ground the AC ground at the boat, but to rely
on the shore ground? Everything I've read says you must ground it at
the boat as a safety precaution against faulty grounding at the dock.
Did I misunderstand something?



The boat is made of PLASTIC. You cannot ground the fiberglass. If you
have a steel hull, I still wouldn't connect the green wire to it. It is
already "grounded" through the seawater. You'd just add to your galvanic
action problem. You may not be able to isolate it as the grounded
equipment is hooked to the hull in lots of places, anyways. Fiberglass
boats are being discussed.
All AC grounds are to be connected to shore power "ground". This insures
you get knocked on your ass if you touch AC hot and the grounded fridge
case. But, that's the way they want it. Buy a plastic cased fridge,
problem solved. The battery charger should have its DC circuit isolated
from its AC circuit. If it's not, I wouldn't buy it. The + and -
charging terminals should be totally isolated from the power-line-
grounded case.

If you tie the "faulty ground" at the dock, let's say it's open from
corrosion or the wire is busted, connected or not to DC ground in the
boat...it's still open. If the plug is wired wrong, the AC box is still
grounded to ground. You'll get knocked on your ass plugging your
grounded plug in if it doesn't explode in your hand before the breaker
trips. Grounding the hot AC line through the faulty hot-connected-to-
green-wire-to-the-boat absurd scenario in the DC to AC interconnected
ground scenario only results in a big flash as the AC current has a
direct path to ground through the engine block/propshaft, tripping the
breaker I hope unless some other absurd scenario has it bypassed....

I'll be absurd, too. Every boater should have a ground detector built
right into the AC breaker panel!