the question you always need to ask is: what happens if I'm wrong?
large ladder, small shock, muscles spasm, thrown clear of ladder, body weight
lands above head, and as happens in all those cases above roughly 7 feet, head
vessels rupture and death within a minute or so..
And on the other hand, if you're right, you don't need to turn off the power.
Am I getting in the way of the thinning of the herd and the improvement of the
species, or am I helping a person who asked so he wouldn't get thinned?
We'll never know - ya gotta do what ya gotta do.
I remember having to do a similar thing whilst working for an AM radio
station some years back.
Whenever we needed to change the tower lighting globes we would place a
rather long wooden step-ladder up against the side of the tower, take off
all metal objects (rings, watches, etc.), climb up the ladder as far as
possible and grab onto the tower rungs with both hands at once (the tower
being live at the time, of course). Once inside the tower you were okay,
but getting back out was harder. If you mistimed your grab, you could get a
nasty RF burn that would take weeks to heal.
Sometimes there isn't really any other way to do it. ;-)
On 12 Dec 2003 03:19:24 GMT, email@example.com (Hobdbcgv) wrote:
Thanks for your concern. This was purely a hypothetical question that
was brought on by watching a seasoned electrician change fluorescent
light fixtures with the power still on.
I asked him, "You work with wires live?"
He basically said that although the ladder was metallic, the shoes on
the ladder were electrically insulated for up to 500 volts or so and
that there was no danger of him getting shocked so long as he never
touched the hot and a neutral or the metal fixture, etc.
I just thought it was interesting that you could grab hold of hot and
not feel anything. I guess if I stood on a plastic milk crate and
touched hot it would be a safer experiment to see for myself.
Certainly you can get shocked.
You could even get electrocuted.
There is a capacity between you and the ground, no matter how well insullated
In fact the Insulation can act as a dielectric increasing the capacity between
you and ground.
I blew out a $500 dollar speaker with the power turned off.
I connected one speaker wire to the audio output and the other brushed against
the chassy.There was a capacitor to ground and to the high side,. and enough
current flowed to blow the speaker with the power turned off.
When working with power, it is always best to not only turn the power off but
disconnect to be sure.
This is not to mention the rf that may be on the wire if it is acting as an
antenna which some one pointed out. You could be a fine ground, through
capacity for that "RF.
I DO NOT FOLLOW MANY OF THESE NEWS GROUPS
To answere me address mail to
I don't think he would have been changing the fixtures live, only the
tubes perhaps? Changing lamps and tubes it is usually quicker and
easier to do this live. Doing such live and holding the tube would not
involve touching live (hot) parts if one takes just a little care. Much
of the fault finding proceedure also has to be done live.
That is fine and no shock would be possible provided he did not
accidently touch ground or neutral. Were I working on live equipment on
a metal ladder which was insulated at the ends, I would be concerned
about the potential risk of someone passing to touch the ladder and
give us both a shock. In such circumstances I would ensure there was
someone to ensure no one did touch the ladder.
In a different thread someone mentioned you would recive a shock as you
and the item you were standing upon is charged up to mains potential.
This is absolute rubbish. In order for something to charge up, the
items you were in contact with would have to comprise a very large
surface area and be closely spaced to the opposite polarity (the
ground). DC is much, much worse in this respect than AC mains.
Some things can be charged up, I have known cable cores when tested
with high voltage DC charge up when the cable length is extremely long,
the insulation extremely good and the conditions very dry. Remove the
cgharging potential and you can stil receive a shock from the cable
If you were considering such a death defying experiment, then please
ensure you do it in the presence of and under the supervision of
Standing on such a crate, you would need to ensure your fingers and
body only contacted the live wire alone, not the neutral or metal
covers, or the wall.
It is potentially a very dangerous stunt if you are not absolutely
certain of what you are doing, none the less those with experience can
do this as part of their daily routine and quite safely get away with
it. I can and do.
Just to give you some idea....
132Kv (that's 132 thousand volt) linesmen often carry out repairs on
live lines. One system dangles the worker from an helicoptor with the
worker quite safely touching the live cable. Birds can and do safely
land on live lines.
true - no one has ever been electrocuted if they don't touch a live source or a
neutral-with -voltage while touching a return -ground or neutral.
However, there are many who thought it wasn't live or there wasn't a return and
are no longer here. Most who aren't here thought there wasn't a path, actually.
And on a personal note - the stuff is out to get you - one that comes to mind
is the "too-cool" guy (not me) on the cage who did the old 460 volt casual
backhand sweep to check for 460 hot - it was a 5K line. He was not dead, just
some nasty 3rd degree burns on his hand and leg as it blew thru his clothes
going to ground
And the personal ones that keep me paranoid-
1) the d___ metal cases/frame that have a short that isn't enough to blow a
fuse or trip a breaker and is grounded by the part being removed. Pinch a hot
in the metal door or clamp so the insulation is crushed almost thru and see
what happens - enough leakage across the insulation to sting pretty well.
2) or drop a bare 460 single phase lead onto a metal frame at the end of a
1000 foot shielded line and be amazed that the 30 amp fuse at the other (box)
end does not blow as the end welds to the frame. (The other engineer was
apparently not aware that a 30 amp fuse is not the same as a 30 amp low energy
let-thru fuse -I did a change out to very-low-energy let thru fuses -both ends,
with signage - that day.)
3) And helpful workmanship - I was stung hard on a completely ground-connected
metal-to-earth machine, with grounded plug and the whole nine yards, because
someone removed a box ground to fix their problem and saw that nothing
happened, so they left it off. Worked fine for months - until....
- on a small crane, small dia wire rope - when I pulled the pin and lifted
the steel rope's connector off the steel eye, and opened "the other ground" -
Fortunately for me, I was paranoid and knew it could be a ground, so as well
as following the usual protocols of tie-off, etc., during the training of some
workers, I did the one hand only, second foot hooked under rail, other hand
away from metal on fiber lanyard of harness, and even then I took a hard sting
thru the gloves, 600 feet up.
A worker using usual procedures would have been knocked out and/or into his
So, my question has been - what if you are wrong?
And - have I ever knowingly changed out a hot fixture? yes, a couple times
across the years - but never if I could turn off power, and always with more
levels of protection than I could count.
I will have to stop reading the Ng's while I am eating...that part about the
5KV burning that mans hand .... well let's put it this way....it was a long
Some very good advice in your post....thanks, Ross
I don't think I have ever seen an electrician use a metal ladder....They
usually use those orange fiberglass jobs. Now that will give you some
insulation! I would be worried that the plastic feet on the ladder would
wear through and ground you!.....later, Ross
A small shock perhaps.. but one large enough to throw you? I, for one, am
After all, if that were true, all them little critters that run up wooden
power poles, cross the insulators, and race out across the wires would get
thrown to the ground - or at least get enough of a tingle to stop in their
tracks and think twice. Or are people different somehow?
The problem is electricians don't work in a vacuum. There are other trades
working around them, dragging things past the ladder. If the metal framer
happens to lay a steel stud next to the ladder and the other end is laying on a
framing member that is shot pinned in, you have a path. If there is a grounded
power tool that gets laid oon the ladder you have a path. If the rubber feet
wear down and the rivets touch the concrete floor you have a path. Your helper
could be grounded when he grabs the ladder creating a path for both of you. For
that matter the electrician could put the ladder down on a piece of metal that
pierces the rubber foot.
I agree that if you are in the middle of a clean room, nobody else around and
you are careful about never being grounded and careful about maintaining your
ladder you *might* never feel a shock but that is not how it works in the real
world. That's why OSHA won't let electricians have metal ladders.
Back in the old maintenance days, we changed fluorescent ballasts live
from a man-lift or sometimes a fiberglass ladder. We found that a
bigger hazard than shock was connecting a 277v ballast live that had a
dead short (like the wire was pinched under the ballast when it was
installed.) Most of the lighting circuits were on 30a or 60a bus plugs
and could make a pretty big flash and boom...the older electricians
held the wire junction close so they could see it.
About ladders and shocking experiences: although there are lots of ways to not
getg shocked, the most common way to get zapped significantly is to use a metal
ladder and touch something you thought was grounded but wasn't.
Think of the scenerio for a minute -- ladder on dirt, you with one hand holding
a rung, and the other touching a fixture that's at 120 V.
Now, if you add in other factors -- ladder on a non-conductive surface, dry
wooden ladder, and so on, you may not, in touching an electrically live
surface, complete a circuit. However, turn the power off! In an emergency one
can wear insulating gloves or take other percautions, but the prudent thing is
to turn the power off.
There is a rule I remember from the safety class I took some 10 years
ago (easy to remember):
When you do some work following 4 steps will keep you safe:
1. IDENTIFY (figure out what is what)
2. ISOLATE (shut off the power, "visible open" is more reliable
than switch in "off" position).
3. TEST (check if it is really off)
4. GROUND (short it to reliable ground)
I would isolate myself from the ground too (with fiberglass ladder
firstname.lastname@example.org (Greg) wrote in message
Because I don't know anything about the ladder materials, the plastic feet
material (is it dielectric?), is the ladder wet or dry, other nearby metal,
what else are you holding, etc. And I don't know if this was a hypothetical
from someone with electrical knowledge, or something that you might be
planning to try, with no electrical knowledge.
Hypothetically, if you are perfectly insulated from any conductive ground
path, which includes not touching any other part of the fixture, then you
won't get a shock (Although technically, you could still feel a very slight
tingle just due to capacitive current, but this would be an extremely low
From a practical standpoint, do not test this theory. Kill the power first.
Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here.
All logos and trade names are the property of their respective owners.