Kevin Ricks wrote:
"Doug Kanter" wrote in message
news
In my bathroom, there's a double wall box with GFIC outlet on one side,
and a pair of switches on the right. One switch controls the fan, and the
other controls the light in the fan. Occasionally, when I switch the fan
OFF, the button in the GFIC outlet pops. I know I need to check all the
connections in this circuit, but still, a question: Why run the fan
through the protected circuit to begin with? Nobody can touch the fan &
light.


I have one of those light/fan combo units in my basement bathroom.
The PO had all fed from a GFCI outlet and 1 switch for both fan and light.
I rewired to have fan and light on separate switches. When I did this the
GFCI tripped every time I turned the fan off. With both light and fan on the
same switch the GFCI never tripped.
I could never figure out why.


The "why" was because the load of the light bulb was still across the
fan when you broke the current to it and it provided enough resistive
loading across the inductance of the motor winding to damp the high
voltage inductive spike which was needling the GFCI.

Jeff

I even swapped GFCI's. I ended up taking the
fan/light off of the GFCI. The GFCI still will trip when turning off the
fan but not very often now.

Kevin










--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Truth exists; only falsehood has to be invented."