It was the case. You two are right. After I blew away the dust with my
compressor, the drill stopped tripping GFCI. See my separate post
FIXED -- THANKS -- drill leaks electricity to case.
It is three wire, but I forgot to check whether there is conductivity
between the case and the ground prong. (I hope so, but I want to make
sure of that). I will try to do so tonight. I know that the ground
wire from the power lead is securely attached to the case, though, so
the check will be more of the CYA variety.
I agree 100%. Most likely it is properly grounded, but I will check
with an ohmmeter to make sure.
On Thu, 23 Feb 2006 14:07:24 GMT, "Lloyd E. Sponenburgh"
You are wrong, transformer breath! ;-P (PPppbltltlt!!)
The GFCI is comparing the exact amount of power going out on the hot
wire and coming back on the white wire, Period. They have two
opposing windings on the same current transformer core, and under
normal operation the currents 'out' and 'in' cancel themselves out to
a sum zero. GFCI's can work on a poorly grounded system on an older
house, though it's not the preferred connection.
Let the power leave on the hot wire and NOT come back on the
neutral, there is current sensed in the transformer. And if it's over
3ma for a Class A device the electronics trips the protection.
The leaked current does not need to come back on the ground
connected to that GFCI. It can ground out to any handy ground source
- a copper water pipe, or a steel stud or structural member tied to
ground in the building, or a grounded natural gas line...
--<< Bruce >>--
Bruce L. Bergman, Woodland Hills (Los Angeles) CA - Desktop
Electrician for Westend Electric - CA726700
The return current has to pass through that one white wire (ground) that
was associated with the black wire (hot) that shared the GFCI in
question. If some current on the black wire bypasses that GFCI by using
some other path to the ground in the panel than the associated white
wire, pop goes the GFCI.
So, leakage from drill case, through Igor, and to ground via the
waterpipes et al, sets up a race condition: Which will pop first, Igor
or the GFCI?
This is the reason to have a well-grounded case. The real danger is
more often that a 110-volt shock will cause a fall or other accident
than direct electrocution.
PS: To take an extreme example, if one puts a resistor from the black
on one circuit to the white of another, both GFCI breakers will pop. At
least in theory, but I recall that many GFCIs are designed to ignore
added current on the white, only reacting when there is more current
leaving on the black than is returning via the associated white.
For the electronically-obsessed, this is achieved by means of a
synchronous detector rectifying the amplified unbalance signal from the
current transformer, the detector feeding a low-pass filter and a
threshold detector. The sign of the detector output varies with the
direction of the unbalance of leaving and returning currents.
If I recall, ten milliamps will do it, so a 110/0.010= 11,000 ohm
resistor capable of at least 110^2/110= 1.1 watts will do, so a 10K
2-watt resistor will do nicely for an experiment.
And, as Dexter would say, "You are STOOOPID!".
Some imbalance must occur between hot and neutral to kick any GFCI... you
even stated that.
Ok... now read my post again. IF there's no _other_ ground path (like the
user, or the drill sitting on a grounded conductive surface) through which
part of the current might leak, AND the GFCI is still tripping, then there
MUST - HAS TO BE - a ground path somewhere in the cord/wiring.
It's simple to understand that current flowing on the hot - which doesn't
have _any_ other path to follow except the neutral - must be matched by
current on the neutral. Balanced currents, no trippy the giffy. Short user
to case to ground, and THEN you have the very situation a GFCI was designed
to protect against.
Not exactly true. The white wire is called Neutral (not ground). It is
a current carrying conductor. There is also a green wire, called
ground, that is not supposed to normally carry current. If some
current leaks and flows through that non current carrying conductor,
or through me, it is called a "ground fault".
I agree with that completely, the dangers from being hit by 110v go
way beyond mere electrocution.
Let's Find Out! I have this deliberately shorted drill, and it's in
front of a grounded platform with an inch of standing water.
Here, let's hand it to my assistant Timmy and have him drill a hole
- Oh, and Timmy you need to take off your shoes and socks for this
experiment, wouldn't want your shoes getting wet, now would we?...
Okay, time to find another Timmy... ;-P
--<< Bruce >>--
On Fri, 24 Feb 2006 05:18:12 GMT, Bruce L. Bergman
Doesn't even have to be directly grounded, Bruce. A capacitive ground
will do it too. In otherwords - leakage to a non-grounded item/person.
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Remember - only 20 milliamp will stop a heart.
Likely it is a powder layer (carbon from the brushes) that sprayed from
themselves to the case. Carbon resistor that gets lower and lower.
Likely a simple cleanup (inside) will do the trick.
@ home at Lions' Lair with our computer lionslair at consolidated dot net
NRA LOH & Endowment Member
NRA Second Amendment Task Force Charter Founder
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