Ed,
What you say is true from the perspective of having effective galvanic
isolation, but there are a couple of design issues that come to mind. In order
for galvanic isolation to work, all wiring grounds to the boat must be
interrupted by a galvanic isolator. This means that if there are two shore
power receptacles then both of them would have to have their wiring grounds
taken to the isolator and then out again to the distribution panel(s). From an
engineering perspective, a wiring ground only needs to have enough capacity to
reliably trip a circuit breaker without catching on fire, but most electrical
codes require that they have the same capacity as the main conductors. In other
words, if you care about regulations and some people on this list have
indicated that they do, then the galvanic isolator would most likely have to
have at least the current capacity of the sum of both shore power receptacles.
According to the instructions that came with a galvanic isolator that a
friend of mine bought last year, a galvanic isolator requires an (optional and
at an additional cost for that particular product) indicator light to be ABYC
compliant. I was shocked at the price tag on the commercial units. The prices
are grossly out of line with what they actually contain.
If you don't care about the light and just want something that works, then a
big enough bridge rectifier, 30 amps for example, with the DC terminals
connected together will work fine and cost a lot less than something that says
"marine" on it. The voltage rating of the rectifier does not matter, just the
current rating. It will provide about 1.2 volts of isolation from the mains
ground.
Steve Thomas
Port Stanley, ON
----- Original Message -----
From: ed vanderkruk via CnC-List
To: cnc-list@cnc-list.com
Cc: ed vanderkruk
Sent: Wednesday, October 28, 2015 11:28
Subject: Re: Stus-List Galvanic isolator - Good idea?
Although there are other practical reasons to have two devices I don't think
the power source of the receptacles applies. Even if the two power circuits
have a selector switch the ground / earth conductor in not switched and almost
certainly common across both on the boat. Thus your boat bridges the ground
circuit of the two incoming power receptacles but they would likely share a
common ground at or near the dock in any case. As the isolator is in-line of
the grounding conductor one properly sized device could, where installation is
practical, handle both power receptacles.
Ed
On Oct 27, 2015 9:31 PM, "Dennis C. via CnC-List" <cnc-list@cnc-list.com>
wrote:
Joel,
I have the Newmar GI-30 on Touche'.
I recently installed two GI-30's on an IP35 with separate 30 amp shore
power inlets. Did some research on combining the two shore power circuits on
one isolator and, in the end, decided it best the isolate each. Part of the
logic is you have no gaurantee that two 30 amp receptacles at a marina will be
wired from the same source.
Dennis C.
On Oct 27, 2015 12:47 PM, "Joel Aronson via CnC-List"
<cnc-list@cnc-list.com> wrote:
And I have 2 30 amp circuits (although I only use one) and the cheap one
can handle both.
I don't mind the neighbors eating my zinc, it is the Max-Prop that is off
the menu!
Joel
On Tue, Oct 27, 2015 at 1:39 PM, Della Barba, Joe via CnC-List
<cnc-list@cnc-list.com> wrote:
My Quicksilver and this one
(http://www.defender.com/product.jsp?path=-1|328|2290032&id=1118395) have the
ABYC required failsafe capacitors. The cheap one does not appear to meet this
standard.
Joe
Coquina
From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of ed
vanderkruk via CnC-List
Sent: Tuesday, October 27, 2015 1:20 PM
To: cnc-list@cnc-list.com
Cc: ed vanderkruk
Subject: Re: Stus-List Galvanic isolator - Good idea?
I put one in when I refurbished my A/C electrical side.
It isolates you from your neighbors which might slow down the zinc
consumption ... unless of course it is issues on your own boat causing you
problems.
Many surveyors would recommend one if you are in a marina with shore
power.
The particular one you have listed doesn't seem to be a 'fail safe'
model as the others in the same catalog category. Which is why they mention a
remote monitor being required.
Ed
On Oct 27, 2015 12:48 PM, "Joel Aronson via CnC-List"
<cnc-list@cnc-list.com> wrote:
Does anyone use one of these:
http://www.defender.com/product3.jsp?path=-1|328|2290032&id=605562
Does it slow/stop electrolysis? Most of the boats on my dock are
plugged in, and I go through a zinc or two a year.
Will an isolater do anything besides lighten my wallet?
--
Joel
301 541 8551
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--
Joel
301 541 8551
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