I guess many of us working around varied voltages have made contact
somewhere along the line. Just before my draft number came up I didn't
start the last term in school and took a job in an electronics factory. By
virtue of a few years EE undergraduate and some radio experience I started
as final inspector, duties being to make sure the things were working,
correct any mis-wiring, replace any new-defective components, make final
alignment and test. Only once did I get hit, and it was with about 600 vdc.
I pulled a metal tube out of a chassis not knowing that some girl on the
line had wired a B+ line to pin 1 (always ground in an octal receiving
tube). I didn't manage to get the tube out; the entire unit, about 100 lbs,
left the bench for the floor about where I had landed. No real damage to the
radio or me, but I did take a short break. Put it back on the bench,
corrected the wiring, got it ready to ship and just kept going. I was more
resilient those days than I am now.
Separate grounding wire in metal conduit? Absolutely. NEC allows a lot of
things that bother me, and leaves a few things out that bother me.
I get the impression that you've had the same ex;perience as I - most cases
are settled after deposition, the negligence being so evident. The real fun
came from the cases where some lawyer thought he could show me up on
cross-examination. Not once did the lawyer win. Dave, K3TX
----- Original Message -----
From: "Dr. Gerald N. Johnson" <geraldj@weather.net>
To: "DAVID HELLER" <dtx@verizon.net>
Cc: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Thursday, February 18, 2010 10:29 PM
Subject: Re: [TenTec] Electric safety
> On Thu, 2010-02-18 at 21:53 -0500, DAVID HELLER wrote:
>> I too do electrical power consulting work, and, like Jerry, have been on
>> cases involving poorly-trained people working on hot stuff - and it's
>> never
>> fun to reconstruct the blame where severe injuries or fatalities are
>> involved.
>
> Sometimes its not been the poorly trained, its been the poorly
> maintained tool or work place and the deceased didn't do anything wrong.
> I have testified in depositions (involving other products problems as
> well as fires accused to be of electrical origin) about 200 times and in
> court about 75 times. I think I have given up that line of work, I hope.
>>
>> Between graduation and grad school I did a stint as Jr.Engineer for an
>> electric utility - and whether beginner or old timer safety was preached
>> day
>> in, day out.
>
> My first job out of college was at Collins in the BC and high power
> transmitter department. We kept test voltages under 100 KV peak and
> radio operating voltages down to 60 KV peak. And we spent much time
> discussing safety and worked safely. The Collins 821A-1 was pretty good
> though a couple of us found 900 volts where it was a hazard without
> protection. Burned a hole in my left index finger all the way to the
> bone and raised the pitch of my voice about two octaves for a couple
> days. My left elbow was grounded.
>>
>> Richards' laughing friends are the stupid ones. Do it yourself is fine
>> for
>> many things, but not power-electric. I hate these home-mechanic books
>> explaining how simple it is to add an outlet, etc. Fine IF and ONLY IF
>> you
>> have had the equivalent of an apprenticeship - or degrees in EE with a
>> bit
>> of hands-on experience - or - adequate fire and life/health insurance.
>
> With care its not all that hard, if you believe ALL the book tells you
> about connections and wire colors but even electricians some times don't
> understand the need for separate ground wires since by their
> understanding of circuits the safety ground adds nothing to the circuit
> function or safety. Just that when the metal case of the tool is
> grounded to the return wire (neutral) and that wire breaks the tool case
> is now at 120 volts with the impedance of the motor in series. When it
> only takes 50 milliamps to put the heart into fibrillation, the
> impedance of a 7 or 15 amp series motor has no effect on the current
> through the heart.
>>
>> Even with supposedly qualified electricians doing the work I've seen too
>> many installations that are booby traps, and too many of them have been
>> sprung before I get to see them.
>>
>> Suggestions to all: two things to avoid: adapters for 3-prong 120 plugs
>> to
>> old style 2-prong (ground terminal cut off is same thing), and the
>> all-too-common in residential construction: blue plastic junction boxes.
>
> I call those adapters "ungrounding adapters." And I live in an old house
> with two wire wiring. I use them on occasion, but I know the condition
> of the tool I'm using them with, usually is also double insulated and in
> a dry place. There are three wire outlets here, but only the circuits
> I've added for computers and hamshack in the basement and for work in
> the garage have proper grounds.
>
> Unfortunately plastic for junction boxes and conduit is approved by the
> NEC. I prefer steel for junction boxes and for all wiring to be in steel
> conduit. The makers of plastics have convinced the NEC committees that
> plastic holds in arcs and holds out fires adequately and certainly in
> wet applications plastic can last longer. In steel conduit I want a
> separate copper safety ground conductor in all pipes and all circuits
> and that can't be left out of plastic. I don't want to depend on the
> conduit connectors for my safety.
>>
>> Will Jerry back me up?
>> Dave K3TX
>
> 73, Jerry, K0CQ
>
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