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

[James Maynard-2]

I'm a new K3 owner, and I chose the K3 in part because of its small
size, because I intend to install it in my boat, which is already
cramped for space.

  I am re-wiring the boat to comply with ABYC (American Boat & Yacht
Council) standard E-11, /AC and DC Electrical Systems on Boats/.  I have
a conventional negative-ground DC system.  The ABYC E-11 standard
requires that in such a system, overcurrent protection (fuse or circuit
breaker) to protect the boat's wiring shall be in the ungrounded
(positive, red) conductor and that the grounded (negative, black or
yellow) conductors in branch circuits (such as the one that one powers
my ham station) shall /not/ have fuse or circuit breakers in them.

The /K3 Owner's Manual/, however, states (under "Specifications", on
page 8) that "[w]hen a battery is used, both sides of the battery cable
should be protected by fast-blow fuses."

I wonder why the manual recommends that the negative lead should be
fused? Can anyone explain this for me?

I intend to wire the K3 power lead with fast-blow fuse in the positive
(red) conductor only, in compliance with the ABYC E-11 standard.  But
,still, I wonder: why does the K3 manual recommend fuses in /both
/conductors: the black (grounded, -12V) as well as the red (ungrounded,
+12V)?

Jim Maynard, K7KK

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[Dave, G4AON]

With car electrics (and a boat may be similar), the reason is that if
the engine grounding strap fails (or is removed and not replaced), the
starter motor can draw current via the radio negative lead which leads
to damage and possibly fire.

73 Dave, G4AON
-----------------
 >I wonder why the manual recommends that the negative lead should be
 >fused? Can anyone explain this for me?
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[James Maynard-2]

On 2011-04-02 01:03 AM, Dave, G4AON wrote:
> With car electrics (and a boat may be similar), the reason is that if
> the engine grounding strap fails (or is removed and not replaced), the
> starter motor can draw current via the radio negative lead which leads
> to damage and possibly fire.
>
> 73 Dave, G4AON
Thank you, Dave, your answer reassures me.

In fact, boats are quite different from cars.  In cars, it is common to
use the chassis as a common ground return.  In boats, this is forbidden.

To avoid ground loops, the various types of "grounds" on a boat (the DC
safety ground [green], the AC safety ground [green or green with yellow
stripe], the lightning ground terminal, the bonding ground for
prevention of electrolysis, the RF radio  ground, etc.) have only one
common point, which is usually the engine negative terminal.  In boats,
only the starter motor is connected directly to the engine negative
terminal.

Other DC circuits on a boat have three (3) wires: the "ungrounded"
normally current-carrying conductor (red, DC+), the "grounded"
current-carrying conductor (black or yellow, DC-) and the "grounding"
conductor which normally does not carry current (safety ground,  green
or bare wire).

Similarly for AC circuits: the "ungrounded" normally current-carrying
conductor (in the USA, black, in the EU, brown), the "ungrounded"
current-carrying conductor (in the USA, white, in the EU, light blue),
and "grounding" conductor that normally does not carry current (in the
USA green, in the EU, green with yellow stripe).

Both the DC and AC safety grounds have only one common point: the engine
negative terminal.  Other circuits, such as the ham radio circuits, are
on the other side of a "main" circuit breaker which cuts both the DC+
(red wire) and the DC- (black or yellow wire).  Likewise, AC branch
circuits are on the other side of a "main" circuit breaker which cuts
both the "hot" conductor ("ungrounded", black in US, brown in EU) and
the "neutral" conductor ("grounded", white in US, light blue in EU).  
The safety ground (green with yellow stripe) is never switched.

So in the scenario that you describe, if the engine grounding strap
should fail or be removed, my boat's main DC circuit breaker will trip,
disconnecting both the DC- (black or yellow) and DC+ (red) conductors
but leaving the "grounding" safety ground (green wire) connected to the
safety ground bus.  The branch circuits downstream of the DC main
circuit breaker then have fuses or circuit breakers only in the
"ungrounded" (red) conductors.

Thank you, Dave;  your explanation reassures me - because I know how
boat wiring differs from automobile wiring.

73,  Jim, K7KK





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[Bob Naumann W5OV]

Jim,

You said:

" Likewise, AC branch circuits are on the other side of a "main" circuit
breaker which cuts both the "hot" conductor ("ungrounded", black in US,
brown in EU) and the "neutral" conductor ("grounded", white in US, light
blue in EU).  
The safety ground (green with yellow stripe) is never switched."

The neutral or white wire in USA residential wiring is never "cut" by a
circuit breaker.  

Both neutral and protective ground circuits are continuous and tie together
only in the main circuit breaker panel (typically) and neither are "cut" by
a circuit breaker.

In the case of normal residential 120/240v single phase circuit panels, both
"hot wires" are indeed broken by a "Main" 2-pole circuit breaker. 240v
branch circuits (2 hots) also use 2-pole breakers. In 120v branch circuits,
only the single "hot" wire(black) is "cut" by a circuit breaker.

73,

Bob W5OV
(retired electrician)

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of James Maynard
Sent: Saturday, April 02, 2011 5:41 AM
To: [hidden email]
Subject: Re: [Elecraft] [K3] Why fuse the negative lead from a battery?

On 2011-04-02 01:03 AM, Dave, G4AON wrote:
> With car electrics (and a boat may be similar), the reason is that if
> the engine grounding strap fails (or is removed and not replaced), the
> starter motor can draw current via the radio negative lead which leads
> to damage and possibly fire.
>
> 73 Dave, G4AON
Thank you, Dave, your answer reassures me.

In fact, boats are quite different from cars.  In cars, it is common to
use the chassis as a common ground return.  In boats, this is forbidden.

To avoid ground loops, the various types of "grounds" on a boat (the DC
safety ground [green], the AC safety ground [green or green with yellow
stripe], the lightning ground terminal, the bonding ground for
prevention of electrolysis, the RF radio  ground, etc.) have only one
common point, which is usually the engine negative terminal.  In boats,
only the starter motor is connected directly to the engine negative
terminal.

Other DC circuits on a boat have three (3) wires: the "ungrounded"
normally current-carrying conductor (red, DC+), the "grounded"
current-carrying conductor (black or yellow, DC-) and the "grounding"
conductor which normally does not carry current (safety ground,  green
or bare wire).

Similarly for AC circuits: the "ungrounded" normally current-carrying
conductor (in the USA, black, in the EU, brown), the "ungrounded"
current-carrying conductor (in the USA, white, in the EU, light blue),
and "grounding" conductor that normally does not carry current (in the
USA green, in the EU, green with yellow stripe).

Both the DC and AC safety grounds have only one common point: the engine
negative terminal.  Other circuits, such as the ham radio circuits, are
on the other side of a "main" circuit breaker which cuts both the DC+
(red wire) and the DC- (black or yellow wire).  Likewise, AC branch
circuits are on the other side of a "main" circuit breaker which cuts
both the "hot" conductor ("ungrounded", black in US, brown in EU) and
the "neutral" conductor ("grounded", white in US, light blue in EU).  
The safety ground (green with yellow stripe) is never switched.

So in the scenario that you describe, if the engine grounding strap
should fail or be removed, my boat's main DC circuit breaker will trip,
disconnecting both the DC- (black or yellow) and DC+ (red) conductors
but leaving the "grounding" safety ground (green wire) connected to the
safety ground bus.  The branch circuits downstream of the DC main
circuit breaker then have fuses or circuit breakers only in the
"ungrounded" (red) conductors.

Thank you, Dave;  your explanation reassures me - because I know how
boat wiring differs from automobile wiring.

73,  Jim, K7KK





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[M0XDF]

I'm not positive (forgive the pun), but I think ideas have changed on that in the UK and you again don't fuse the -ve lead, but I'll need to check.
73 de M0XDF, K3 #174, P3 #108
--
In our day and age it seems that Common Sense is in short supply.  If you don't have any Common Sense - get some Common Sense and use it.  If you can't find any Common Sense, ask for help from somebody who has some Common Sense.  Is Common Sense divine?

On 2 Apr 2011, at 09:03, Dave, G4AON wrote:

> With car electrics (and a boat may be similar), the reason is that if
> the engine grounding strap fails (or is removed and not replaced), the
> starter motor can draw current via the radio negative lead which leads
> to damage and possibly fire.
>
> 73 Dave, G4AON
> -----------------
>> I wonder why the manual recommends that the negative lead should be
>> fused? Can anyone explain this for me?
> ______________________________________________________________

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[Don Wilhelm-4]

  Where will the current will flow if there is a fault?  That is the
question.

There are two things involved here - wiring the radio negative directly
to the battery or wiring it to the vehicle chassis.  It does make a
difference because of the way most vehicle batteries are tied on the
negative terminal.

If one wires both positive and negative directly to the battery, the
negative should be fused to protect the RADIO in case of a fault between
the battery and the engine block.  It is not a safety issue.

Note carefully that the battery negative is wired both to the engine
block and to the chassis by direct wires from the battery negative.  If
the battery were tied only to the engine block and then the chassis were
also tied to the engine block (as was pointed out in the case of the
boat), the failure mode would not exist.
And it is all because the radio is grounded to the chassis through the
antenna connection in addition to the negative lead.  If both these
grounds go to the chassis instead of the battery negative, the problem
solved by the fuse in the negative lead would not exist.

If the radio negative is connected to the vehicle chassis, the problem
does not exist and the negative lead should NOT be fused.

73,
Don W3FPR

On 4/2/2011 9:40 AM, David Ferrington, M0XDF wrote:
> I'm not positive (forgive the pun), but I think ideas have changed on that in the UK and you again don't fuse the -ve lead, but I'll need to check.
> 73 de M0XDF, K3 #174, P3 #108
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[Samuel Strongin]

Who's on first     Sam kf4yox

Sent from my iPhone

On Apr 2, 2011, at 10:19 AM, Don Wilhelm <[hidden email]> wrote:

>  Where will the current will flow if there is a fault?  That is the
> question.
>
> There are two things involved here - wiring the radio negative directly
> to the battery or wiring it to the vehicle chassis.  It does make a
> difference because of the way most vehicle batteries are tied on the
> negative terminal.
>
> If one wires both positive and negative directly to the battery, the
> negative should be fused to protect the RADIO in case of a fault between
> the battery and the engine block.  It is not a safety issue.
>
> Note carefully that the battery negative is wired both to the engine
> block and to the chassis by direct wires from the battery negative.  If
> the battery were tied only to the engine block and then the chassis were
> also tied to the engine block (as was pointed out in the case of the
> boat), the failure mode would not exist.
> And it is all because the radio is grounded to the chassis through the
> antenna connection in addition to the negative lead.  If both these
> grounds go to the chassis instead of the battery negative, the problem
> solved by the fuse in the negative lead would not exist.
>
> If the radio negative is connected to the vehicle chassis, the problem
> does not exist and the negative lead should NOT be fused.
>
> 73,
> Don W3FPR
>
> On 4/2/2011 9:40 AM, David Ferrington, M0XDF wrote:
>> I'm not positive (forgive the pun), but I think ideas have changed on that in the UK and you again don't fuse the -ve lead, but I'll need to check.
>> 73 de M0XDF, K3 #174, P3 #108
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[Jim Brown-10]

On 4/2/2011 3:40 AM, James Maynard wrote:
> In fact, boats are quite different from cars.  In cars, it is common to
> use the chassis as a common ground return.  In boats, this is forbidden.

While the chassis serves as an acceptable return for DC current, using
it in this manner is a recipe for AC problems, like alternator while and
RFI.  Ham gear should ALWAYS be powered by  paired conductors running
directly from the power source, preferably a twisted pair.

73, Jim Brown K9YC
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[Jim Brown-10]

On 4/2/2011 10:45 AM, Jim Brown wrote:
> While the chassis serves as an acceptable return for DC current, using
> it in this manner is a recipe for AC problems, like alternator while and
> RFI.  Ham gear should ALWAYS be powered by  paired conductors running
> directly from the power source, preferably a twisted pair.

Bad fingers -- I meant to say "alternator whine."  :)

73, Jim K9YC
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[Joe Subich, W4TV-4]

 > While the chassis serves as an acceptable return for DC current, using
 > it in this manner is a recipe for AC problems, like alternator whine
 > and RFI.

In addition, it's a recipe for ignition noise and corona noises since
using the chassis of the vehicle as a DC return makes every noise
source in the vehicle (plus antenna return currents) "common" to the
transceiver power supply.   Consider the impedance between the
transceiver's chassis connection and the negative terminal of the
battery to be equivalent to the modulation choke in an old AM
transmitter ... every noise and all of the antenna "return" current
modulates the DC reference (DC return) of the transceiver!

Proper installation of communications equipment calls for separately
fused power connections directly to both terminals of the battery
and a substantial common mode choke in the antenna feedline at the
feedpoint of the antenna.

73,

    ... Joe, W4TV


On 4/2/2011 1:45 PM, Jim Brown wrote:

> On 4/2/2011 3:40 AM, James Maynard wrote:
>> In fact, boats are quite different from cars.  In cars, it is common to
>> use the chassis as a common ground return.  In boats, this is forbidden.
>
> While the chassis serves as an acceptable return for DC current, using
> it in this manner is a recipe for AC problems, like alternator while and
> RFI.  Ham gear should ALWAYS be powered by  paired conductors running
> directly from the power source, preferably a twisted pair.
>
> 73, Jim Brown K9YC
> ______________________________________________________________
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>

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[Don Wilhelm-4]

  Joe and all,

Tom Rauch W8JI (whom I believe is well versed in the installation of
radios in vehicles) has disagreed with that about a year ago on this
reflector.  Those interested in his statements may want to search the
archives.

73,
Don W3FPR

On 4/2/2011 4:09 PM, Joe Subich, W4TV wrote:
> Proper installation of communications equipment calls for separately
> fused power connections directly to both terminals of the battery
> and a substantial common mode choke in the antenna feedline at the
> feedpoint of the antenna.
>
> 73,
>
>      ... Joe, W4TV
>
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[James Maynard-2]

Right, Bob.

What you say is true of AC residential wiring.

Boats are different.  The so-called "main" AC breaker on a correctly
wired boat breaks both the "hot" wire(s) -- black or in 120/240 VAC
single phase, black and red) and the "neutral" (white) wire -- coming
from the boat's shore power inlet. Also, boats are required (by ABYC
E-11) to have a reverse polarity indicator or alarm to alert the user if
he plugs his shore power cable into an incorrectly wired shore power
pedestal outlet at the marina.

The marina's shore power outlet at the pedestal near your slip is, from
the point of view of the requirements for residential or factory wiring,
a BRANCH outlet, and one in a particularly damp and hazardous location,
where a Ground Fault Circuit Interrupter would be appropriate.  (Most
marinas lack GFCIs however.)  The shore power coming on board a boat at
its shore power inlet has its neutral and safety ground conductors tied
together only at the main power inlet for the whole marina.  At the
shore power pedestal at your slip, there is usually a noticeable
different in AC voltage between the neutral and safety ground.  (If
indeed, there *is* a safety ground -- too often marinas are wired
incorrectly!)

This can be a particular hazard in marinas in fresh water.  If there
were a wiring fault aboard your boat - or a nearby boat - there can be
an AC potential gradient in the fresh water surrounding the boats, and
anyone swimming nearby can be electrocuted by that AC voltage gradient.  
(People are more conductive than fresh water, but less conductive than
salt water. So-called ESD -- electro-shock drowning -- can and does occur.)

So I am wiring my boat acccording to the current ABYC E-11 standard
rather than according to the National Electric Code that applies to
residential wiring.  I am installing ELCIs (Equipment Leakage Circuit
Interrupters) for each shore power inlet, and I am also installing an
isolation transformer, wired according to E-11, with the case connected
to the boatside ground, and the shield between the windings connected to
the shoreside neutral (white wire coming from the marina's shoreside
pedestal).

You are correct, Bob, in describing residential wiring.  But boats are
different!

Jim Maynard, K7KK

At 2011-04-02 05:14 AM (Pacif Daylight Savings Time), Bob Naumann wrote:

> Jim,
>
> You said:
>
> " Likewise, AC branch circuits are on the other side of a "main" circuit
> breaker which cuts both the "hot" conductor ("ungrounded", black in US,
> brown in EU) and the "neutral" conductor ("grounded", white in US, light
> blue in EU).
> The safety ground (green with yellow stripe) is never switched."
>
> The neutral or white wire in USA residential wiring is never "cut" by a
> circuit breaker.
>
> Both neutral and protective ground circuits are continuous and tie together
> only in the main circuit breaker panel (typically) and neither are "cut" by
> a circuit breaker.
>
> In the case of normal residential 120/240v single phase circuit panels, both
> "hot wires" are indeed broken by a "Main" 2-pole circuit breaker. 240v
> branch circuits (2 hots) also use 2-pole breakers. In 120v branch circuits,
> only the single "hot" wire(black) is "cut" by a circuit breaker.
>
> 73,
>
> Bob W5OV
> (retired electrician)
>

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[Jim Brown-10]

On 4/2/2011 1:09 PM, Joe Subich, W4TV wrote:
>   a substantial common mode choke in the antenna feedline at the
> feedpoint of the antenna.

Yes.

73, Jim K9YC
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[Jim Brown-10]

On 4/2/2011 2:06 PM, Don Wilhelm wrote:
> Tom Rauch W8JI (whom I believe is well versed in the installation of
> radios in vehicles) has disagreed with that about a year ago on this
> reflector.

I don't often disagree with Tom, but sometimes I think he's mistaken.  
One place we differ is that he recommends powering gear from the
alternator rather than the battery.  Tom has done a lot of work with
serious mobile installations, and he has reasons for his recommendations.

73, Jim K9YC
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[M0XDF]

Hmmm, interesting thread, this from a radio colleague who is also into 4x4, off-roading and response, some of this has already been said here, but note the last paragraph:

The logic is that if the main chassis bonding strap fails, and the radio is connected to the battery, then the path from the radio mounting bolts through the negative lead becomes the earth path for the entire vehicle.

I have heard stories of other, higher resistance paths becoming overloaded including one of a red-hot glowing throttle return spring.  

The current UK recommendation is to NOT fuse the negative lead but to bond it to the chassis close to the battery so that it can't become part of that failure circuit, rather than to the battery directly.  

73 de M0XDF, K3 #174, P3 #108
--
Too many parents make life hard for their children by trying, too zealously, to make it easy for them. -Johann Wolfgang von Goethe, poet, dramatist, novelist, and philosopher (1749-1832)

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[W8JH]

Sadly enough we had a local man in his early 20's who was killed by ESD when he dove in to retrieve a pair of glasses a woman had dropped off the dock.  This was in fresh water (Lake Erie) at South Bass island.  A bit OT for sure but I do think about that when in a marina with power.

Joe,  W8JH, K3 1713

[James Maynard-2]

Not completely off-topic, Joe.

It bears on why I am wiring my boat to ABYC standards rather than the
model National Electric Code (NEC) from the National Fire Protection
Association (NFPA) -- and on why I am *not* fusing the negative lead in
runs from my batteries to branch circuits such as the one that feeds my
ham equipment.

The recent additions to the ABYC E-11 standard (effective July 2009)
requiring ELCIs (Equipment Leakage Circuit Interrupters)  were added as
a result of a similar ESD incident some years ago here in the Portland,
Oregon area.  Kids were floating downstream past  a local marina's docks
to cool off on a hot summer day. One of them, 12-year old Lucas Ritz,
was floating on his back with his PFD keeping his head out of the water,
when he decided to join his mom, who was walking along the marina in
parallel with the kids and keeping an eye on them.  As he swam toward
his mom, he was electrocuted by the AC voltage gradient in the fresh
water.  Mom saw that her son was in trouble and leaped in the save him,
as suffered electric shock herself, but fortunately did not drown.  Dad
came rushing to the scene, too late.  He suspected that it wasn't a
simple drowning, researched the matter, and changed careers to become a
teacher of ABYC standards and promoting changes to those standards to
prevent future so-called electro-shock drownings (ESDs), some of which,
like his son's are not drowning at all, but electrocutions.

See this link for the story:
<http://www.huffingtonpost.com/terry-gardner/esd-hidden-danger-in-fres_b_693454.html>

I recently heard the dad, Kevin Ritz, tell the tale at a seminar he gave
at the marina where my boat is being refurbished, and I had read about
the story earlier in the local boating press.  So I ordered an ELCI
(Equipment Leakage Circuit Interrupter) with an automatic disconnect
relay to cut both the hot and neutral leads coming from the shore power
inlet on my boat in case of either a fault current being detected
flowing through the neutral lead from the shore power cord or in case of
reverse polarity (white wire "hot", black wire "neutral").  And I added
an isolation transformer, too.

All these things led me to trust in the ABYC standards rather than the
K3 Owner's Manual in deciding how to wire the DC power cable that leads
to my K3.  And led me to pose the question that started this thread.

  Jim K7KK -- K3 #5263
"Remember, Ignorance is the Mother of Adventure!" -- Hagar the Horrible

In 2011-04-03 12:20 PM, W8JH wrote:
> Sadly enough we had a local man in his early 20's who was killed by ESD when
> he dove in to retrieve a pair of glasses a woman had dropped off the dock.
> This was in fresh water (Lake Erie) at South Bass island.  A bit OT for sure
> but I do think about that when in a marina with power.
>
> Joe,  W8JH, K3 1713
>

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[Jim Brown-10]

On 4/3/2011 8:25 PM, James Maynard wrote:
> It bears on why I am wiring my boat to ABYC standards rather than the
> model National Electric Code (NEC) from the National Fire Protection
> Association (NFPA) -- and on why I am*not*  fusing the negative lead in
> runs from my batteries to branch circuits such as the one that feeds my
> ham equipment.

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
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[James Maynard-2]

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]

Jim,

It's been a few years since I had to be concerned with the NEC on a daily
basis, but I would expect that the answer to your question is yes regarding
the marina wiring.

I also expect that this thread will have run its course and be ended soon.

73,

Bob W5OV


-----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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