GFI question

Why should switching power to a GFI trip it? A GFI works on difference on current flowing in 2 parts of the circuit. Both are being started and stopped at exactly the same time.

My holiday light setup involved a GFI that was switched like that, I used if for about 40 days, and had not one trip that occurred when it was being switched.

Quite correct.

BUT a un-powered GFCI can permit some safe hazards to continue.

It is better to have the GFCI always powered and have the switch AFTER the GFCI.

A powered GFCI will detect and "trip" a "fault" between neutral and ground.

A GFCI will NOT detect incorrect wiring whereby neutral and HOT are switched. But a powered up GFCI will still trip when either of the two load wires have a 5ma path to ground.

A further advantage of putting the GFCI before the switch is that it will be indoors and less subject to contamination from aerosols.

Regardless, it's a GOOD idea to TEST the devices. They DO fail and outside units fail more often. And they don't necessarily fail "safe."

I have two plug in GFI devices and they sometimes trip after a power outage. A friend of my had some GFI outlets in his garage do the same thing. I have NO idea why it happens but it does happen.

I wired them that way, so the GFCI would also be a switched receptacle. The other way (switch after GFCI) would require adding a second receptacle.

Why assume it's outside? My switch and GFCI were both inside.

I have a portable GFI that's intended to be used with extension cords or portable tools. It's in the form of a 15 A extension cord (male plug on one end, female socket on the other) with a GFI in between. It drops out any time the input power is lost. You have to "reset" it initially whenever you plug it into a new power source.

I assume this is a safety feature - you don't really want a power tool restarting on its own after it has stopped because the line power went away. So some GFIs do drop out on power loss, just like a magnetic starting switch for a large power tool.

On the other hand, the wall-outlet type of GFI does not trip on power loss. It behaves more like a circuit breaker.

Dave

Hi, No. An exmple. Bathrooms are GFI protected. Turning lights on/off in the bathroom does not trip breaker. There are GFI outlet and GFI breaker.

Note that in houses wired according to code, the GFI-protected outlets in the bathroom are on a different circuit from the bathroom lighting. Nevertheless, Tony is correct; the GFI will not trip if you wire the switch into the circuit. Make *very* sure you wire the switch in the hot line, not the neutral line.

Yours aye, W. Underhill