On Tue, 6 Sep 2011 13:02:32 -0400, "Eric" wrote:



"Doug Miller" wrote in message ...

On 9/5/2011 4:00 PM, Eric wrote:


"m II" wrote in message ...

Dougy gets different water out of his garden hose than he puts in too! LOL

Need some basic electrical theory there Dougy or STFU.
------------------
"Doug Miller" wrote in message ...
Inductive loads such as those presented by electric motors put the
return current slightly out of phase with the supply current. If the
amplitude of the phase difference exceeds 20mA, the GFCI trips.

==================

I would be sure Doug Miller was using an analogy and doesn't actually
believe currents could be different in a series circuit. Most electrical
people
should know better than that.

Cut the guy some slack.


There *is* a slight phase delay when the circuit supplies an inductive
load -- which means that during a time window measured in milliseconds
the currents *are* different. That can be enough to trip a GFCI.

Obviously, over anything but an extremely brief time period, the
currents are exactly the same.

Equally obviously, "m II" is in my killfile for good and valid reasons. :-)

==============

Sorry, but that "delay" theory is not correct.

You may have this confused with inductance where an inductive coil
electrical component exhibits a reluctance to current change.

Remember "current" flows through an inductive component and never into one
without returning to the source. There will never be a difference in current
in and out due to an inductive component or any component in an electrical
circuit (static electricity theory using high voltage notwithstanding).

A changing voltage may create a phase lagged current through an inductor
(coil) but not a current phase lagged to itself, whereby current enters a
component but does not leave at. That would be impossible.

However, this is not a two-terminal device. There is capacitance to ground,
you're missing. This complicates the issue greatly. ...and yes, it is a
problem, or at least was. I believe recent GFCIs have fixed this problem. The
codes have been changed to reflect this.

Review Kirchhoff's Current Law. (loosely stated) The sum of currents
arriving at any point must equal zero.

This is not what makes GFCI units trip from fan motors. Current leakage
faults to ground or other conductors causing a current "differential" (ANSI
Standard C37.2 - 87) is the only trigger.

Capacitance.