On Wed, 23 May 2007 12:46:41 -0400, Wayne.B
wrote:

Whatever the cause of neutral and ground being tied together
somewhere, I suspect it has been that way for quite awhile.

The discovery process continues, thanks to everyone who has chipped in
with advice.

Here's the latest:

The AC neutral and safety ground (normally white and green) are
definitely tied together. As I understand it, this is an ABYC
standard although somewhat controversial. The AC safety ground and
the boat DC grounds appear to be totally isolated however.

I was able to buy a non-contact AC current probe at Northern Tool this
afternoon for $16. It is very useful for tracing out circuits and I'm
beginning to make some sense out of the wiring scheme by turning on
one breaker at a time.

The two bus bars that I located earlier are both for safety grounds
not neutral wires. Tomorrow I'll remove some more panels and try to
find the neutral bus. It's got to be hidden away somewhere. Checking
all of the major circuits with a current probe, there appears to be no
detectable return flow to the safety ground bus bars.

Wayne.B wrote:


The AC neutral and safety ground (normally white and green) are
definitely tied together. As I understand it, this is an ABYC
standard although somewhat controversial. The AC safety ground and
the boat DC grounds appear to be totally isolated however.


This seems to say that tying the AC
neutral and grounding wires together is
required by the ABYC standard. The
antecedent to the OP's "this" is ambiguous.

My copy of the ABYC standard is not
ambiguous. It says:

"Neither the shore-grounded (white)
neutral conductor nor ungrounded
current-carrying conductors shall be
grounded on the boat."

In the case of an onboard isolation
transformer, the transformer's secondary
"neutral" is connected to the boat's AC
ground system. But the "shore-grounded
(white) neutral conductor) is NOT
grounded on the boat. This is also an
ABYC standard.

Since it has not been revealed whether
the OP's boat employs an isolation
transformer, it is not clear whether his
boat is in violation of an ABYC standard.

DIY electricians are cautioned to inform
themselves of relevant standards, safety
practices, and electrical fundamentals
before undertaking boat re-wiring tasks.
In addition to potential safety hazards,
any surveys reporting improper wiring
may impose economic costs as well.

Chuck

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Wayne,

You bought a tool ?? I am concerned ... I don't think your taking the
warning provided by both Chuck and I to heart. I didn't here a "thanks
guys your right", I am meeting your concern by doing x,w,z, etc.

Instead your next post contains an incorrect reference to ABYC, and
you will buy a new tool ???

Your just buying a tool, now? No experience using it ? I know it
looks simple to use a tool to trace one wire, but preventing stray
current that can either kill or corrode (then sink your boat), has a
set of best practices behind it that are lengthy and honesty difficult
to impliment fully for a novice. In the trade, new guys spend months
working with and being double checked by experienced electricians on
AC wiring before they handle it on their own, and they still take
short cuts as it is time consuming to do it right even when you know
it all.

Chuck gave a great example of one possible outcome, there are many
more.

You want to continue to enjoy boating don't you ?
Just do the right thing and stop now.

On 24 May 2007 12:07:46 -0700, b393capt
wrote:

Instead your next post contains an incorrect reference to ABYC, and
you will buy a new tool ???

I appreciate your concern but I'm not really a novice at all this.

Please explain my "incorrect reference to ABYC".

On May 24, 6:10 pm, Wayne.B wrote:
On 24 May 2007 12:07:46 -0700, b393capt
wrote:

Instead your next post contains an incorrect reference to ABYC, and
you will buy a new tool ???

I appreciate your concern but I'm not really a novice at all this.

Please explain my "incorrect reference to ABYC".

Wayne,

What ever word you want to use for your experience level ... if your
not aware of the dangers (you asked us what they were remember) and
best practices (corrosion avoidance/stray current prevention, use of
ground & nuetral to protect humans on board and potentially in the
water around your boat, mounting and connecting wires to preventing
fires, etc.), your not qualified to do this alone. If your want to
save some money and run and/or mark wires yourself with help from this
board, you clearly need an experienced electrician to at least check
your work when your finished, before hooking up to shore power again.

Marking all the wires yourself will save you easily over 80% of the
cost of having an electrician do everything (but you got to do it
right), but still could involve an expense of over $500-$800 to have
someone carefully check the work. If your not ready to spend that
money, put off the project and go boating instead.

Now read that first paragraph again, because that $500-$800 will get
you someone who:
- Is aware of the dangers that the ABYC standards are attempting to
prevent.
- Might not be an expert, but clearly understands the ABYC standards
and best practices that will prevent stray current (under water).
Stray current hurts your exposed metal parts under your boat, destroys
the zinc anodes on the boats around you, and represents a risk to
people in the water like the local diver who might be cleaning under
the boat next to you.
- Could inspect connections, etc. to spot fire hazards that might not
be apparent or connections that are simply prone to failure.
- In addition to checking your work, will spot hazardous conditions
caused by people before you ... and really, you cannot have any faith
in someone who didn't use color coded wiring.

Dan

p.s. check me out, I post on several boards, the electronics expert on
the beneteau 393 group, contibute to Ben Ellison's marine electronics
blog, and am on a readers advisory board for an offshore sailing
magazine. Not once, has someone posted that I am alarmist, and few
errors have been noted in my postings.

On 25 May 2007 06:19:04 -0700, b393capt
wrote:

- In addition to checking your work, will spot hazardous conditions
caused by people before you ... and really, you cannot have any faith
in someone who didn't use color coded wiring.

Thanks, we both agree the wiring leaves a lot to be desired but
redoing the whole thing at one time is too big an undertaking for now.
At the moment I'm just trying to straighten out the worst of the
previous owner(s) haywire and not make anything worse.

The color coding issue is common to most boats built in the far east,
Singapore in my case. Although it's a mystery to us, they did have a
standard that they were following and there are number tags on every
wire that was factory installed. Now it's my job to try and
understand it, and fix the worst of any short comings. This is a 50
ft trawler with a lot of hidden wiring, 2 generators, an inverter and
probably over a mile of circuits. Even with all of the PO's haywire
it has been doing OK for 26 years and many thousands of sea miles.

Wayne ?

I half expected to see a post here that you bought yet another tool,
maybe a clamp on ammeter would probably be next, and asking more
questions.

I truly hope after the warnings we gave you, you spent memorial day
weekend out boating instead of working on your A/C

On 29 May 2007 19:09:08 -0700, b393capt
wrote:

I half expected to see a post here that you bought yet another tool,
maybe a clamp on ammeter would probably be next, and asking more
questions.

You guessed it, I did buy a clamp on ammeter, nice little digital unit
at Home Despot for about $50. You really can't have too many tools,
and any excuse will do... :-)

As you already knew or suspected, something in the AC wiring system is
totally FUBAR. There is a significant current imbalance (amps)
between the black wire and neutral on both 50 amp legs indicating
leakage back through the green wire. The same situation exists under
generator power, with shore power totally disconnected. Any ideas on
how to safely test for leakage into the water?

I finished up rewiring the battery charger, confident that I had in
fact located neutral and green correctly, and color coded the wires
with tape for future reference.

I made a few attempts to further isolate the leakage issue but nothing
conclusive yet. One thing that is bothersome is that both 50 amp legs
have the imbalance, even though each leg should in theory be isolated
by its own double pole breaker.

Much more work needs to be done obviously. I will get to the bottom
of it eventually, and with professional help if necessary. If you're
anywhere near SW FL stop by sometime and join in the fun.

On Wed, 23 May 2007 23:52:26 -0400, Wayne.B
wrote:


The AC neutral and safety ground (normally white and green) are
definitely tied together. As I understand it, this is an ABYC
standard although somewhat controversial. The AC safety ground and
the boat DC grounds appear to be totally isolated however.

NO! ABYC, CSA and probably other standards require that the shore
power neutral (white) and the safety ground (green) MUST NOT be
connected on board. (They will be connected somewhere ashore.)

If you have an on-board power source (generator, inverter, or
isolation transformer), then while using that power source, the
on-board neutral and safety ground must be tied together at the
source.

In any case, the on-board safety ground (green) must be tied to the
vessel ground. The shore-side safety ground must be tied to the
vessel ground either directly, or through a galvanic isolator.


--
Peter Bennett, VE7CEI
peterbb4 (at) interchange.ubc.ca
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On Thu, 24 May 2007 19:11:33 -0700, Peter Bennett
wrote:

The AC neutral and safety ground (normally white and green) are
definitely tied together. As I understand it, this is an ABYC
standard although somewhat controversial. The AC safety ground and
the boat DC grounds appear to be totally isolated however.

NO! ABYC, CSA and probably other standards require that the shore
power neutral (white) and the safety ground (green) MUST NOT be
connected on board. (They will be connected somewhere ashore.)

OK, Peter and Dan, you are both being very helpful, thanks. Please
bear with me for one or two more iteration levels into my
understanding.

Here's the situation: The boat has two 120 volt, 50 amp AC legs,180
degrees out of phase with a neutral wire circuit in the middle similar
to house wiring. Each 50 amp leg can be isolated with its own double
pole breaker. All three wires (hot-neutral-hot) are easily
accessible.

I went out today and bought a digital clamp on ammeter. My theory is
that if I have leakage through a ground path, it should show up as a
current imbalance between the hot wire and neutral wire, similar to
the logic in a GFI.

So here is my next stupid question, sorry. If one of the loads has
the safety ground and neutral wire inadvertantly reversed, it seems to
me that this should show up as a current imbalance as I previously
outlined. In your opinion, is this a valid test for that condition?

If so, my next plan is to test every circuit and load, one at a time,
to make sure that nothing was haywired in the past, and that nothing
is leaking current to ground.

Stupid question number 2. I believe that if I have two equal
resistive loads, one on each leg, that the net neutral wire current
should read zero. Can you verify if that assumption is correct?