On Sat, 13 Dec 2008 23:42:49 -0700, Tony Hwang
wrote:

mm wrote:
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
safe, but...

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
adapter???

That would be unsafe, if it happens.
Hi,
If you think like that nothing electrical is safe.

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.

Then you wasted people's time if you knew the answer.


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.

Your eyes area't important; only reality is important.

Certainly the particular device which leaks 110 into a plug that is
expected to be 6 or 12 volts would be unsafe.

Not necessarily: There is some leakage, even through the air.

Before it happens
fuse will blow inside

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.

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.


or something will pop cutting off power,

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
ground.

What if some toddler or pet puts it in his mouth?

Good reason for GFCI's if mains is appearing anywhere it shouldn't.


also
whatever the wall wart is feeding, that device has a fuse and reverse
polarity protector, etc. built in for safety.

Not everything has those. Certainly not cheap things. Are either of
these UL requirements? I don't think so.

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.


But I was never worried about the device being ruined. If an
important part of any device fails, often that kills the device. That

Right.

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
it).

That's a lot of what "safety" is about in the eyes of the agencies.

So now what do you say?

Please, see above.