Re: T&T: Battery Chargers & Inverters
Scott Welch wrote: "Every fish boat I've ever seen uses Square D
household-style breaker panels for AC, and that's exactly what I put in
Island Eagle. May not look "nautical", but on the other hand the panels cost
$22 and the breakers we're under $10. Performance has been flawless."
While I generally agree with Scott, in this case, I do not. Square "D" is a
fine manufacturer of residential and commercial electrical equipment, but
marine installations involving generators and inverters are -electrically -
much more complex than ordinary residential installations. Residential
electrical systems are not designed to be routinely disconnected from the
power grid ("shore power") and run by gensets and inverters. "Solar"
residential installations that are designed for these applications have
significant additional control circuitry and code compliance issues than
"plain vanilla" homes. The electrical safety and fire prevention codes that
apply to residential distribution appliances cannot - in many regards - meet
the safety requirements of marine installations. Yes, you could probably
use a Square "D" panel as a sub-panel on a boat, but for the main
disconnects on a boat, you need breakers that break both the hot and neutral
lines. Likewise with the feedpoint breakers on gensets and inverters.
Residential breakers don't do that. Houses don't move, so their electrical
systems don't have to accommodate moving. Houses have permanent ground
rods, boats can't have ground rods. And on and on...
A huge problem here is that people with a seat-of-the-pants knowledge of
residential electrical wiring can often "get things working" on a boat.
Often in doing so, they corrupt and compromise the safety of the boat's
electrical system installation. My advice would be to stay with electrical
equipment and switchgear rated for conformance to marine use codes, and
avoid residential equipment. This strategy will preserve the design safety
of the boat's system for it's users (you, your crew, guests, maintenance
personnel, pets, divers, etc), and also foreclose the possibility of
potential future (and expensive to correct) survey non-conformances.
Just my advice.
Jim
Peg and Jim Healy aboard Sanctuary,
currently at Rondout Creek, Kingston, NY
AGLCA # 3767
MTOA # 3436
Do commercial fishermen switch to shore power or do they stay full-time on
generators like tugs?
Ron Rogers
Jim has stated this well and I would agree with him 100%. He only touched on
one issue and that is the potential for a survey failure, causing the
insurance policy to be denied until corrected, or if you have an insurance
claim at some point you may find the claim denied based on the electrical
issues. Chuck
To follow our adventures, go to
http://trawler-beach-house.blogspot.com/
http://sea-trek.blogspot.com/
On Mon, 7/20/09, Jim Healy gilwellbear@gmail.com wrote:
While I
generally agree with Scott, in this case, I do
not. Square "D" is a
fine
manufacturer of residential and commercial electrical
equipment, but
marine installations involving generators and inverters are
-electrically -
much more complex than ordinary residential
installations. Residential
electrical systems are not designed to be routinely
disconnected from the
power grid ("shore power") and run by gensets and
inverters. "Solar"
residential installations that are designed for these
applications have
significant additional control circuitry and code
compliance issues than
"plain vanilla" homes. The electrical safety and fire
prevention codes that
apply to residential distribution appliances cannot - in
many regards -
meet
the safety requirements of marine installations. Yes,
you could
probably
use a Square "D" panel as a sub-panel on a boat, but for
the main
disconnects on a boat, you need breakers that break both
the hot and
neutral
lines. Likewise with the feedpoint breakers on
gensets and
inverters.
Residential breakers don't do that. Houses don't
move, so
their electrical
systems don't have to accommodate moving. Houses have
permanent ground
rods, boats can't have ground rods. And on and on...
A huge problem here is that people with a seat-of-the-pants
knowledge of
residential electrical wiring can often "get things
working" on a boat.
Often in doing so, they corrupt and compromise the safety
of the boat's
electrical system installation. My advice would be to
stay with electrical
equipment and switchgear rated for conformance to marine
use codes, and
avoid residential equipment. This strategy will
preserve the design safety
of the boat's system for it's users (you, your crew,
guests, maintenance
personnel, pets, divers, etc), and also foreclose the
possibility of
potential future (and expensive to correct) survey
non-conformances.
Just my advice.
Jim
"Jim Healy" gilwellbear@gmail.com writes:
Yes, you could probably
use a Square "D" panel as a sub-panel on a boat, but for the main
disconnects on a boat, you need breakers that break both the hot and neutral
lines. Likewise with the feedpoint breakers on gensets and inverters.
Residential breakers don't do that.
This is a good point. My main selector switches all break the neutral. The on
ly exception to this is the 30 amp breaker on the main shore power cord. That
has a very direct run (24 inches) to the isolation transformer. While double-
pole breakers are readily available (I use one as the genset disconnect), I c
ould not see any justification for breaking both legs.
By the way, I only used the Square D panels for AC.
Scott Welch
Product Manager, Open Text Collaboration and Social Media Group
www.opentext.com
905 762 6101
"Things turn out best for people who make the best of the way things turn out
." - John Wooden
Scott,
The "justification" for breaking both legs is the NEC, and by extension to
the marine environment, the ABYC, which bases it's AC standards on the NEC.
The NEC states that the neutral and ground in an AC distribution system
should be connected together at the "source" for end use attachments; never
at sub-panels or other points in the system. For shore power, the "source"
is defined to be a specific point on-shore in the marina's electrical
infrastructure. Depending on the size of the marina and its electrical
system design organization, that point could be for one dock, or for the
entire property. If its a residential dock on the creek in the backyard,
it's the main service entrance panel for the residence. HOWEVER, if the
boat has a genset or an inverter/charger or both, the "source" will be the
genset when it's running or the inverter/charger when the inverter/charger
is being used in invert mode. ALL of these devices require that both the
neutral and the hot legs be broken by attaching switchgear.
Jim
Peg and Jim Healy aboard Sanctuary,
currently at Rock Creek, Pasadena, MD
AGLCA # 3767
MTOA # 3436
From: Scott H.E. Welch [mailto:swelch@opentext.com]
Sent: Monday, July 20, 2009 11:20 AM
To: Jim Healy
Cc: trawlers-and-trawlering@lists.samurai.com
Subject: Re: T&T: Battery Chargers & Inverters
"Jim Healy" gilwellbear@gmail.com writes:
Yes, you could probably
use a Square "D" panel as a sub-panel on a boat, but for the main
disconnects on a boat, you need breakers that break both the hot and neutral
lines. Likewise with the feedpoint breakers on gensets and inverters.
Residential breakers don't do that.
This is a good point. My main selector switches all break the neutral. The
only exception to this is the 30 amp breaker on the main shore power cord.
That has a very direct run (24 inches) to the isolation transformer. While
double-pole breakers are readily available (I use one as the genset
disconnect), I could not see any justification for breaking both legs.
By the way, I only used the Square D panels for AC.
Scott Welch
Product Manager, Open Text Collaboration and Social Media Group
www.opentext.com
905 762 6101
"Things turn out best for people who make the best of the way things turn
out." - John Wooden
"Jim Healy" gilwellbear@gmail.com writes:
The NEC states that the neutral and ground in an AC distribution system
should be connected together at the "source" for end use attachments; never
at sub-panels or other points in the system. For shore power, the "source"
is defined to be a specific point on-shore in the marina's electrical
infrastructure.
Not quite. If you run an isolation transformer, the "source" is defined as th
e secondary of the transformer.
Scott Welch
Product Manager, Open Text Collaboration and Social Media Group
www.opentext.com
905 762 6101
"Things turn out best for people who make the best of the way things turn out
." - John Wooden
I'm not where I can get at my standards, so I can't check this out right
now. I do not believe it's a correct interpretation, since transformers can
and do short internally, and they are located in the end attachment part of
the distribution system, where by definition, there can't be two sources.
Peg and Jim Healy aboard Sanctuary,
currently at Rock Creek, Pasadena, MD
AGLCA # 3767
MTOA # 3436
From: Scott H.E. Welch [mailto:swelch@opentext.com]
Sent: Tuesday, July 21, 2009 12:44 AM
To: Jim Healy
Cc: trawlers-and-trawlering@lists.samurai.com; swelch@opentext.com
Subject: Re: T&T: Battery Chargers & Inverters
"Jim Healy" gilwellbear@gmail.com writes:
The NEC states that the neutral and ground in an AC distribution system
should be connected together at the "source" for end use attachments; never
at sub-panels or other points in the system. For shore power, the "source"
is defined to be a specific point on-shore in the marina's electrical
infrastructure.
Not quite. If you run an isolation transformer, the "source" is defined as
the secondary of the transformer.
Scott Welch
Product Manager, Open Text Collaboration and Social Media Group
www.opentext.com
905 762 6101
"Things turn out best for people who make the best of the way things turn
out." - John Wooden
"Jim Healy" gilwellbear@gmail.com writes:
I'm not where I can get at my standards, so I can't check this out right
now. I do not believe it's a correct interpretation, since transformers can
and do short internally, and they are located in the end attachment part of
the distribution system, where by definition, there can't be two sources.
Remember, an isolation transformer is a "load" to shore power (the primary wi
nding) and a "source" to the boat (the secondary winding). Hence the AC neutr
al should be bonded to the AC ground on the secondary side of the isolation t
ransformer.
Scott Welch
Product Manager, Open Text Collaboration and Social Media Group
www.opentext.com
905 762 6101
"Things turn out best for people who make the best of the way things turn out
." - John Wooden
Tuesday, July 21, 2009, 6:02:08 AM, Scott wrote:
SHEW> "Jim Healy" gilwellbear@gmail.com writes:
I'm not where I can get at my standards, so I can't check this out right
now. I do not believe it's a correct interpretation, since transformers can
and do short internally, and they are located in the end attachment part of
the distribution system, where by definition, there can't be two sources.
SHEW> Remember, an isolation transformer is a "load" to shore power (the primary wi
SHEW> nding) and a "source" to the boat (the secondary winding). Hence the AC neutr
SHEW> al should be bonded to the AC ground on the secondary side of the isolation t
SHEW> ransformer.
SHEW> Scott Welch
SHEW> Product Manager, Open Text Collaboration and Social Media Group
SHEW> www.opentext.com
SHEW> 905 762 6101
To clarify:
The shore-side AC neutral is only connected to one side of the
transformer primary, and not to vessel ground.
The on-board neutral and on-board ground are connected to one
secondary terminal of the transformer and to vessel ground.
--
Peter Bennett, VE7CEI Vancouver, B.C., Canada
Ennos 31 "Honeycomb"
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca
Peter Bennett peterbb4@interchange.ubc.ca writes:
The shore-side AC neutral is only connected to one side of the
transformer primary, and not to vessel ground.
The on-board neutral and on-board ground are connected to one
secondary terminal of the transformer and to vessel ground.
Not only is this correct, it is in fact the major point of an "isolation" tra
nsformer: it removes the DC connection between the DC vessel ground on your b
oat and the DC vessel grounds on all of the other boats around you. Without a
n isolation transformer there is a DC connection between your ground and the
ground of every other vessel on the same AC system as you.
Scott Welch
Product Manager, Open Text Collaboration and Social Media Group
www.opentext.com
905 762 6101
"Things turn out best for people who make the best of the way things turn out
." - John Wooden