[K3] Why fuse the negative lead from a battery?

[Bob Naumann W5OV]

>From the Document scope for the 2011 NEC:

90.2 Scope. (A) Covered. This Code covers the installation of electrical
conductors, equipment, and raceways; signaling and communications
conductors, equipment, and raceways; and optical fiber cables and raceways
for the following: (1) Public and private premises, including buildings,
structures, mobile homes, recreational vehicles, and floating buildings (2)
Yards, lots, parking lots, carnivals, and industrial substations (3)
Installations of conductors and equipment that connect to the supply of
electricity (4) Installations used by the electric utility, such as office
buildings, warehouses, garages, machine shops, and recreational buildings,
that are not an integral part of a generating plant, substation, or control
center. (B) Not Covered. This Code does not cover the following: (1)
Installations in ships, watercraft other than floating buildings

I suspect that the docks and their associated wiring would be considered a
"floating building" from the NFPA's perspective.



-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of James Maynard
Sent: Monday, April 04, 2011 3:40 AM
To: [hidden email]
Subject: Re: [Elecraft] [K3] Why fuse the negative lead from a battery?

On 2011-04-04 12:38 AM, Jim Brown wrote:
> It's critical to realize that Codes and Standards are written for specific
situations. NEC applies ONLY to premises wiring, and to some

> extent, to wiring connected to premises wiring (like a standby
> generator, or an accessory building, like a garage powered from the same
> service).  It does NOT apply to vehicles, or boats, or to the power
> company's wiring outside the premises.
>
> When Standards and Codes are written, very smart and experienced
> engineers cogitate and discuss all the possible implications of the
> requirements of the proposed standard, trying very hard to consider how
> the system would react to any of the myriad of things that might go
> wrong, and with serious attention both to how things are done in the
> real world, and to the laws of physics.For about ten years,  I've been a
> part of that process as a member of the AES Standards Committee, and am
> a principal author of all of our published standards on EMC. A typical
> Standard takes 3-5 years to be conceived, written, and adopted. I have a
> great deal of respect for my colleagues, and others  who do this, and
> for the resulting standards and codes.
>
> 73, Jim Brown K9YC

Indeed.  The "Scope" section of a standard is Very Important Indeed.  So
if I am to make disparaging comments about the use of NEC, it behooves
me to purchase my own copy of it.   Thank you for making that point.

I, too, have been involved in the standards development process, first
for computer codes and character sets (I was a member of ANSI X3L2, the
same committee that had -- before my participation -- given us ASCII,
the American National Standard Code for Information Interchange.  Later
I was a member of a committee under RTCA, developing standards for the
use of GPS in the navigation systems of aircraft.)  These people work
hard, and it's a lot of fun meeting people from other companies and
government agencies involved in the developing those standards.

Do you know, Jim, whether the definition of "premises" in the NEC would
include an entire marina? Not the boats kept in the marina, but the
wiring of such structures as floating docks?

73, Jim Maynard K7KK




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[Bob Naumann W5OV]

Even further, Article 555 "Marinas and Boatyards" specifically addresses
these types of installations.

555.3 Ground-Fault Protection: (paraphrased) is required by either the main
breaker being a GFCI device or each (every) branch circuit can be fed from a
GFCI device.

The NFPA allows reading of the 2011 code online if you register with them
for free - you cannot "copy" and paste the text from it, but you can do a
"print screen" and get an image of the page you're reading which is OK I
guess. That will at least let you print the pages you're interested in.

http://www.nfpa.org/onlinepreview/online_preview_document.asp?id=7011SB#

There is also an additional document that can also be read online focused on
Marinas and Boatyards -  NFPA 303: FIRE PROTECTION STANDARD FOR MARINAS AND
BOATYARDS

http://www.nfpa.org/aboutthecodes/AboutTheCodes.asp?DocNum=303

There is no "search" function, but you can browse the table of contents and
navigate from there in these documents .

73,

Bob W5OV

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Bob Naumann
Sent: Monday, April 04, 2011 6:13 AM
To: [hidden email]; [hidden email]
Subject: Re: [Elecraft] [K3] Why fuse the negative lead from a battery?

>From the Document scope for the 2011 NEC:

90.2 Scope. (A) Covered. This Code covers the installation of electrical
conductors, equipment, and raceways; signaling and communications
conductors, equipment, and raceways; and optical fiber cables and raceways
for the following: (1) Public and private premises, including buildings,
structures, mobile homes, recreational vehicles, and floating buildings (2)
Yards, lots, parking lots, carnivals, and industrial substations (3)
Installations of conductors and equipment that connect to the supply of
electricity (4) Installations used by the electric utility, such as office
buildings, warehouses, garages, machine shops, and recreational buildings,
that are not an integral part of a generating plant, substation, or control
center. (B) Not Covered. This Code does not cover the following: (1)
Installations in ships, watercraft other than floating buildings

I suspect that the docks and their associated wiring would be considered a
"floating building" from the NFPA's perspective.



-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of James Maynard
Sent: Monday, April 04, 2011 3:40 AM
To: [hidden email]
Subject: Re: [Elecraft] [K3] Why fuse the negative lead from a battery?

On 2011-04-04 12:38 AM, Jim Brown wrote:
> It's critical to realize that Codes and Standards are written for specific
situations. NEC applies ONLY to premises wiring, and to some

> extent, to wiring connected to premises wiring (like a standby
> generator, or an accessory building, like a garage powered from the same
> service).  It does NOT apply to vehicles, or boats, or to the power
> company's wiring outside the premises.
>
> When Standards and Codes are written, very smart and experienced
> engineers cogitate and discuss all the possible implications of the
> requirements of the proposed standard, trying very hard to consider how
> the system would react to any of the myriad of things that might go
> wrong, and with serious attention both to how things are done in the
> real world, and to the laws of physics.For about ten years,  I've been a
> part of that process as a member of the AES Standards Committee, and am
> a principal author of all of our published standards on EMC. A typical
> Standard takes 3-5 years to be conceived, written, and adopted. I have a
> great deal of respect for my colleagues, and others  who do this, and
> for the resulting standards and codes.
>
> 73, Jim Brown K9YC

Indeed.  The "Scope" section of a standard is Very Important Indeed.  So
if I am to make disparaging comments about the use of NEC, it behooves
me to purchase my own copy of it.   Thank you for making that point.

I, too, have been involved in the standards development process, first
for computer codes and character sets (I was a member of ANSI X3L2, the
same committee that had -- before my participation -- given us ASCII,
the American National Standard Code for Information Interchange.  Later
I was a member of a committee under RTCA, developing standards for the
use of GPS in the navigation systems of aircraft.)  These people work
hard, and it's a lot of fun meeting people from other companies and
government agencies involved in the developing those standards.

Do you know, Jim, whether the definition of "premises" in the NEC would
include an entire marina? Not the boats kept in the marina, but the
wiring of such structures as floating docks?

73, Jim Maynard K7KK




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[AC7AC]

CONTENTS DELETED

The author has deleted this message.

[Terry Schieler]

Thank you all!  Very informative.  

I just sent the article link to the president of our lake condo's owner's
association.  I know our marinas have GFCI protection (and assume they are
tested regularly), but we have a number of large boats with onboard AC
systems (inverters and/or generators as well as shore power) and suggested
they consider requiring those boats to have ELCI's operating.

Terry, W0FM


-----Original Message-----
From: Ron D'Eau Claire [mailto:[hidden email]]
Sent: Monday, April 04, 2011 10:06 AM
To: [hidden email]
Subject: Re: [Elecraft] [K3] Why fuse the negative lead from a battery?

I just want to thank you guys for this thread. Even though I have a number
of years working on shipboard electronics, my experience was on large,
deep-water vessels that didn't use dockside power connections. This has been
very educational.

Among all of those like me who might have read about it here, this awareness
might well save a life.

73,

Ron AC7AC



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[Jim Brown-10]

On 4/4/2011 1:40 AM, James Maynard wrote:
> Do you know, Jim, whether the definition of "premises" in the NEC would
> include an entire marina? Not the boats kept in the marina, but the
> wiring of such structures as floating docks?

I'm not enough of an expert on NEC that I could offer a detailed opinion
on that in the context of a marina, which is a rather special use, for
the reasons you and others have pointed out. BUT -- the generally
accepted, broad definition of "premises" in the context of NEC would be
a conventional land-based home or business. It would apply to the LAND
wiring, and of wiring connected to LAND-based wiring -- for example,
mains power outlets on the dock. Such outlets would be required to be
protected by a GFCI, which acts as a circuit breaker and cuts off power
if leakage current.is detected.

GFCI's are required to kill power if the leakage current exceeds 5 mA,
which is the current at which electrical shocks can begin to hurt you.
They work simply by comparing the currents on the phase (hot) and
neutral conductors.

If land-based power were brought onto a boat, the parts of NEC with
which I'm familiar would seem to require outlets on the boat for
land-based 120V or 240V power to be GFCI-protected (or a GFCI-like mains
breaker, which is widely used in the UK for premises wiring, where they
are called a Residual Current Detector, or RCD). There's a discussion of
this on page 22 of my Power and Grounding tutorial.

73, Jim Brown K9YC


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[Jim Brown-10]

Thanks Gene.I;m not the guy who cares about boats, so  I'm posting this
to the list so that the folks who do will see your response.

73, Jim K9YC

On 4/4/2011 4:09 PM, Gene Fuller wrote:

> Hi Jim,
>
> Marinas are indeed covered under the NEC. However, almost all power
> outlets for boats are either 30A or 50A. As you may know, GFCI
> protection is not generally required for any circuit/outlet greater
> than 20A.
>
> At the same time, boats are specifically excluded from the NEC, so no
> real requirement there either. Most newer boats have individual
> circuit GFCI for AC outlets, but this a rule in the "advisory" ABYC
> specs, not a regulation. The double breaker for the ungrounded (black)
> and grounded (white) conductors is also an ABYC rule. All boat
> builders follow these rules today, but the situation was quite
> different 15 or 20 years ago.
>
>
> 73,
> Gene
> W4SZ

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