I was looking at an FAQ for some small appliance that runs or
recharges from an AC adapter, a black box that plugs into the AC and
lowers the voltage to 12 or less, and maybe changes it to DC.
And it said this was safe, and I too have been assuming these were
Has anyone heard of a short in one of these adapters that sent 110
volts to the thing that was supposed to charge or run off the
That would be unsafe, if it happens.
Extremely unlikely, the primary and secondary are wound on separate
plastic bobbins, it would be very difficult for them to short together.
The transformers are class II and are impedance protected too, so they
will not heat up enough to catch fire even when shorted. In a nutshell,
you should be more worried about getting struck by lightning than one of
these wall warts electrocuting you.
If you think like that nothing electrical is safe. Before it happens
fuse will blow inside or something will pop cutting off power, also
whatever the wall wart is feeding, that device has a fuse and reverse
polarity protector, etc. built in for safety. So now what do you say?
How is it do you think I think? Did you not see the way I phrased the
question that I anticipated either a No answer, or maybe 1 or 2 cases
out of hundreds of millions.
On the other hand, if I was wrong and it happens a lot, it would be
unsafe, but this wouldn't make everything electrical unsafe. Their
safety would remain unchanged in my eyes.
Certainly the particular device which leaks 110 into a plug that is
expected to be 6 or 12 volts would be unsafe.
I don't think they all have fuses. Even the ones that do only have
the fuse on one pole, and the plugs are rarely if ever polarized, so
the unfused prong can easily be plugged into the hot slot.
Something? Like the circuit breaker in the basement? Sure, when it
gets above 15 amps the breaker will trip. Don't you think it would
still be worse to have 110 volts where only 6 are supposed to be?
Or you mean something in the circuit? By the time a non-fuse blows, a
burn or worse is pretty likely for anyone in between 110v and a
What if some toddler or pet puts it in his mouth?
Not everything has those. Certainly not cheap things. Are either of
these UL requirements? I don't think so.
But I was never worried about the device being ruined. If an
important part of any device fails, often that kills the device. That
devices that use adapaters are in separate, disconnectable parts means
maybe that wouldn't happen, but if it does, no big deal. By "not
safe" I meant not save for people (or pets, now that i think about
Then you wasted people's time if you knew the answer.
Your eyes area't important; only reality is important.
Not necessarily: There is some leakage, even through the air.
ALL are fused in one way or another; you may not be able to change the
fuse because it's a fusible link, but it's there. Too high a temp will
stop them from working; often permanently.
Good reason for GFCI's if mains is appearing anywhere it shouldn't.
Yes, the fusing is required by all the safety agencies; UL, CSA, CE,
etc.. The fusing is often a fusible link inside the transformer, but
it's got to be there. Reverse polarity protection isn't necessarily
part of the requirements; it's often handled by the item it powers but
if it's there it has to be tested.
That's a lot of what "safety" is about in the eyes of the agencies.
Clare, thanks for a very helpful answer.
On Sun, 14 Dec 2008 09:06:21 -0500, "Twayne"
Where did I say I knew the answer?
I said "anticipated". That's not the same as "knew".
I only addressed this because the previous poster said "If you think
But you're wrong. Few people know what reality is. They base their
actions on what they think reality is. That's what I do, and I'll bet
you do too.
How does leakage in the air make something safe that is unsafe? How
would a second danger make a first danger go away?
Also, I've never measured anywhere near 110 volts between the air and
ground. Have you?
I've looked inside a bunch of them, and I don't believe all have
Even if they all did, you ignore my point about the fuse (or fusible
link) being only on one end of the coil, on one prong of the plug, and
how easy it is to plug that prong into the neutral and the unfused
prong into the hot slot.
It is a good reason, but we all know that not ever receptacle has a
GFCI on it.
So my question stands, don't you agree?
Are you only talking about the transformer, the wall wart? Because
at this point, the previous poster and I were talking about "whatever
the wall wart is feeding". I think you were so eager to contradict
me that you didn't read closely. I don't believe fusing is required
in the device powered by the wall wart. I've taken many low-voltage
things apart that don't have fuses or fusible links.
Didn't someone once say "The eyes of agencies area't important; only
reality is important"?
As I said, they use class II transformers, the primary winding itself is
the fuse in most of them, it is hair thin wire. These windings are on
separate plastic bobbins over the iron core, and the windings are
themselves insulated wire. The chances of somehow getting 120V on the
output are so tiny that they are for all intents and purposes zero. You
put your life on the line every time you get into a car, plane, or ship,
or even walk out your front door. There are so many daily activities and
items that are orders or magnitude more likely to hurt you than a
transformer plug that it is not even worth thinking about and this is
If you are really worried about electrical safety in your house, replace
all the receptacles that almost certainly use the spring loaded backwire
terminals I've been complaining about lately. Install AFCI breakers on
all the circuits, inspect the condition of light fixtures regularly for
damaged sockets or burned wires, those are all things that really can
and do cause shocks and fires.
Yes. I saw your answer and I appreciated it. But I'd already told
HeyBub that because of him I had one less thing to worry about, so I
didn't reply to later posts that said similar things to HeyBub's.
Even though your reply was more detailed. I hope I was not rude.
I'm not worried at all. I'm debating Tony and Twayne to try to
resolve details of what they said, but it's already clear to me that
the claim in the FAQ I saw was justified, that their adapter was safe.
I sort of know the inventor/maker of the product, and I was concerned
about his forthrightness or naivete, whichever applied. I really
wasn't concerned about my personal safety at all. I will still leave
my phone machine adapter plugged in all the time, and the one for the
cordless phone, and I've provided switches for some but that is only
to save electicity and not because I'm worried about either fire or
Check your sources. I have NEVER posted political nonsense. I have only
responded to the true believers who have posted that which is provably an
absurd fantasy. I don't start contentious conversations; I have no desire to
rile up those of lesser patience. But proselytizing about global warming,
political machinations, the virtues of colonic irrigation, or the health
benefits of beets, will be challenged.
I agree with what I take to be your position - that home repair should
remain unsullied by extraneous ramblings. I also believe, however, that
gratuitous dogma should be met with objective facts wherever it raises its
You knew what the answer was going to be, yet still asked anyway. You
didn't say you were looking for clarification/verification/ etc.. Many
people do what I mentioned - but I probably could have phrased it a lot
better, I admit, as you also could have. NBD IMO.
Ah, I see.
No, not wrong in this case anyway. This case is governed by the laws of
physics, ruled & regs, even legal entities and "voluntary" rules & regs,
As for reality of all, well, that's a subject change I prefer not to
get into. I deal in facts and rules, not opinions and suspicions.
Not certainly, but certainly possibly<g>. It could result in anything
from no visible change going on to a fire or lots of smoke, but it's not
to easy to be certain it would become unsafe. Those are the kinds of
things that hopefully Safety Agencies test for when they approve a
product as "safe".
You snipped the explanatory part of that; I never said anyting about a
second danger making a first danger go away. There is always current
flow through anything, whether it be air or the best insulator that
exists. It may be imperceptible without very expensive equipment and a
lot of theory, but ... that does respond to the text you snipped out.
No, I haven't, and wouldn't even try. I have however, done so, during
the design of high-voltage lightning simulators. A lightning strike,
for instance, is through the "air", whatever the "air" happens to be at
that particular moment in time, and may travel for miles through the
air. Again, this was a response to something you brought up and to
which I responded, in such a way as to prevent the topic from changing.
Fusible links are seldom visible. Very often they are buried within the
winding, because that's where the max temperature is going to build up
and begin to melt the lacquer or whatever is used to separate the wires
from each other and from other windings (primary to each secondary,
etc.). They are also, unfortunately, unrepairable. Once a link goes,
the item is shot.
BTW, a fusible link may be nothing but a piece of wire of any length
within the xfmr. An entire xfmr winding may be composed of only one
type of wire, all of it with the characteristics of a fusible link, and
all acting as such. Actually, that's fairly common in many xfmrs today;
it's no longer that expensive a prospect to use. Fusible wire can even
be used in all windings, not just the primary; very often the
secondaries will also have the same design if a shot ckt say or other
possible point of entry could cause enough heat to create problems.
UL/CSA have some very long articles and papers on the subject also if
you're interested in research at all.
No, not at all. It's just that, unless I misunderstand you, the
polarity of the hot/neutral are not relevant. A circuit is a circuit
and the laws of heating and dissipation etc. do not depend on whether
the polairty is correct. There is absolutely no difference in anything
based on whether the hot/neutral are reversed or not. A circuit is a
circuit. The whole thing depends on an expanding/collapsing magnetic
Either you mis-spoke, or I misunderstand you, or you are really much
more ignorant about electrical theory than I have given you credit for.
With a piece of wire with a total length of x, the power dissipated by
the link within it will be exactly the same.
Do I agree that not all receptacles are protected by a GFCI? Certainly.
Should they be? Well, that depends on a few things but in general, yes.
I don't see your question any longer so you may have to pose it
lol, if you think I was anxious to respond to you in particular, then so
be it! I'm not going back to old posts just to pursue the
Taking your above comment apart:
Devices supplied by the wall warts may or may not require fusing.
That's something that there just isn't any one size fits all answer for.
In addition, a lot of weight is given to warnings and noticed permanelty
placed on the products about the dangers of using any power supply but
the one sold with/for the device under consideration.
It will basically depend on whether, within that device, the maximum
difference of potential is 42V or more at any instant in time, meaning
the comparison of ac, DC and ac/DC plus each to earth or if it's Class
II, to the neutral. In addition, the fusible component may or may not
be visibly apparent; it only has to match the fusing/time curves for the
relevant safety tests.
In essence, the whole thing comes down to 90% what the wall wart is or
isn't, and 10% what the accompanying equipment it is meant for. A xfmr
can either carry its own safety approvals, or only be a component,
whereby the safety approvals are only applicable when used in a certain
way with certain things.
lol, who do you think enforces the safety testing, even performs the
tests? And guess what: They base it on .. wait for it .. reality! If
you meant me, I don't think that's a correct quote, but whether it is or
not isn't important. What is important is the troll-bait appearance of
the comment; either that or stress that you shouldn't let a post on a
newsgroup cause for you. AFter all, almost everyone is human<g>!
That's part of the reason most countries in NA and Europe require safety
testing on products; to insure the designs are such that it can't happen
with any normal single failure outside of neglect or misuse or damage to
the products. No UL, CSA, CE or equivalent markings, don't buy it; it
wasn't tested and it's illegal to sell it.
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