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From: mike senko (no email)
Date: Tue Oct 02 2001 - 08:19:36 EDT
Eric,
Comments in-line:
----- Original Message -----
From: "Eric Thompson" <>
To: "mike senko" <>
Sent: Monday, October 01, 2001 4:46 PM
Subject: Re: lv-ab: Galvanic currents
> Mike,
> The boat that was losing it's zincs every 30 days is brand
> new (6 months old). A Benateu331. I wonder haw you really
> spell that name? Anyhow, My boat is not bonded. My boat has
> NO ground to the sea, no AC no DC NADA. My boat also has the
> most Mickey Mouse, crappy, dangerous wiring I have ever seen
> in my life! Whomever wired this boat needs to get a job he's
> qualified to perform! Yes, I will be rewiring BOTH the AC
> and DC circuits. Yes I will be installing a Dynaplate for DC
> ground. BOY I'd love to have an isolation transformer! Got
> one to spare? 30 amp rated please.
If you go the route of the isolation transformer, you might look for a place
that sells used medical equipment. I heard that was a possible source for
relatively inexpensive equipment.
Beneteau eh? My guess is either someone swapped ground and nuetral
on one of his outlets or there is a problem with a battery charger/inverter,
or the DC and AC grounds are tied together. You should be able to go
6 months on a zinc. If you connect one externally (i.e. one of those fish
type
that you attach to a grounded shroud) will probably go a year or more. Not
only
is he going through too much zinc, but his neighbors are too.
One other thought, there could be a problem with the dock wiring. Perhaps
there is a section that is in the water. I would contact the marina and
have
them check it out. Someone could get killed.
> But, being a disabled person living on $1077 a month in
> northern California I won't be buying any transformers any
> time soon unless I find one for under $200. Sooo I'll be
> installing a Galvanic Isolator (with monitoring circuitry)
> for under $200 instead. I will not be bonding my boat. I
> WILL however be replacing my through hull fittings with the
> reinforced plastic types.
Sorry about the disability. I have significant health probelms too.
Since your income is limited, I would not be inclined to purchase
a galvanic isolator. Since you mentioned you want to become
a ham operator (a very worthwhile and satisfying persuit),
I would use the $200 saved by not buying the galvanic isolator
and purchase all bronzethrough-hulls and ball valves, then bond
them with the engine and any metal tankage. I would also forgo
the Dynaplate (another cost savings) and mesh laminations into
the hull if you have metal tanks or cannot get to the keel bolts if
you have them. The metal tanks would have to be below the
waterline to be of use, and close to the hull.
With the bonding of the keel, engine, water tanks, and through hulls, you
are
capacitevely coupling to the sea for the ground portion of your random wire
ham radio antenna, plus installing a DC ground for the radio chassis.
In the case of the dipole type antenna, the only ground
required is for the radio chassis (the difference between an RF ground and
DC ground). If you use an auto tuner for the antenna, you can construct
ground radials
and run them under the floor of the boat right up next to the hull if you
don't have below-the-water tankage.
You will learn all of this when you study for your ham license.
So right now, I would be more interested in making the boat electrically
safe
(I don't like boat fires!) and efficient for the AC side (more to your
question)
and worry about the DC side after you have passed the ham tests and have
a good feel for what you want to do.
> I am not currently a ham operator but I will be going down
> that road eventually. I am going to laminate the accessible
> areas of my hull with copper mesh. I have seen this work
> well for others but they were transmitting marine SSB. I
> hope it will work for Ham bands too.
SSB and Amateur bands: same basic areas of the radio spectrum,
(HF) just different freq's. and methodology. The SSB has much tighter
frequency controls than the ham radios and they use channels. Ham radios
allow you to dial into a frequency via a tuning knob and/or preset memory
channels that you get to program (the SSB radio is pre-programmed and cannot
be changed). Some SSB radios will allow you to talk on the ham bands and
it is legal to do so. SEA is one manufacturer that comes to mind. SSB radios
are
significantly more expensive too. Ham radios can be "opened up" to talk on
any
frequency, including SSB freq's, but it is illegal to do so. However in an
emergency
anything goes in the world of communications and it would then be legal to
communicate
on ANY freq that you can make contact on with a Ham radio.
> After all that, IF I could get a transformer I'd install
> it, forget the Galvanic Isolator, then connect the
> (arbitrary)neutral output to the Dynaplate AND the safety
> (green) wire for my outlets. Oh Yeah, I'll use my outlet
> tester to verify my wiring. I'll also be using marine grade
> 6 AWG wire, gold plated ring lugs sealed with adhesive lined
> heat shrink tubing, AND a GFCI for protection.
I wouldn't go overboard here. 120 volts doesn't require the same
wire sizes as DC circuits. As for gold plated connectors, another
waste of money. I would use some silicone paste on the wire ends
to seal them up when attaching to an AC receptacle and leave it at that.
10 gauge wire will be more than adequate. Ancor sells pre-tinned wire
and would be a good choice.
Pick up copies of the books I referenced. They are inexpensive and
will save you more some money. ARRL also produces a very nice
handbook for amateur radio and is also a good source. In fact, when
studying for your ham exams I would join ARRL. They have great
study guides and morse code tapes that take the pain out of learning
the code (another very useful skill!)
As for the GFCI, the ones I have used and seen in the stores are
all 15amp - more than enough for the application unless you want
to try to run a full 30 amps through the receptacle in which case you
would not be using the household type receptacles anyway, but something
like your dock power connectors (Hubbel twist-locks).
Remember, GFCI is for Ground Fault Circuit Interrupter. This device
senses the gound line and when there is too much gound current it will
open with a current level less than what will kill you at 120 volts AC.
The 15 amp rating is standard house-hold outlet connectors and is
all you can plug into it. Max would be 20 amps for the blade type
connectors. 20 amp cords will have one of the blades turned side ways.
I have not seen a GFCI rated at 20, but I haven't looked either. Also,
15 amps is half of the total available current at the dock (assuming 30
amp service).
They are cheap insurance and I think can be had
at a local hardware store for less than $15. Same quality as what you will
get from WMP and probably cheaper (I didn't check prices).
> Do you know of a source for GFCIs rated for 30 amps? The
> Marineco ones listed in the West Marine catalog say 15 amps.
>
> Eric Thompson
> S/V Procrastinator
> South San Francisco
>
Mike
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