[R-390] GFI devices (was "New Owner")

[Roy Morgan]

At 08:20 AM 10/6/2006, Dave Maples wrote:
>All: Considering that the GFI is probably protecting more than the outlet
>where the R-390A is plugged in (e.g. the laundry room or kitchen) ...

Dave and others,

Some further comments on GFI (Ground Fault Interrupter) devices:

Dave is thinking of the case where the circuit breaker panel has a GFI 
circuit breaker that feeds a number of outlets on one circuit.  A more 
common situation is where the OUTLET itself is the GFI device.  (It could 
be that modern electrical installations have the GFI circuit breakers, I 
don't know. I have always lived in houses much older than modern.)

A duplex GFI outlet has two teensy buttons located between the two outlets: 
one is often red but not always.  If you push the one marked "test", it 
causes a ground fault condition and the thing should trip. The other button 
pops out. Push the other one back in to reset the device. It's smart to do 
this from time to time to make sure the thing is still working.  The 
GFI  circuit breakers likely have a similar function.  It makes sense to me 
to never paint a GFI outlet.  The paint might keep it from functioning 
correctly.  (Of course if I was on the IEC committee that developed the 
standard(s), I would have thought of that.  Maybe they did.)

A Duplex GFI outlet can be wired to feed other normal outlets and protect 
them.  You should suspect this is the case if you have, say, at the kitchen 
counter, a number of outlets and only one of them is a GFI device.  (NOTE: 
It can also be wired INcorrectly to feed other outlets and NOT protect them.)

It's a VERY good idea to have and use one of those little outlet testers 
you can buy at the home store. They cost about $9 and are the best money 
you can spend for household electrical safety. They have a row of neon 
lamps and can tell you if you have a mis-wired socket.  There are a number 
of ways an outlet can be mis-wired or at fault.  In some cases, the thing 
will work just fine even though there is trouble.  Buy one of those 
testers, and test every outlet you can find.  It doesn't take long, and can 
avoid big troubles.  If you have an outlet which has one side on all the 
time and one side controlled by a wall switch, test both sides. 
Electricians and installers are supposed to know what they are doing, but 
they are human and make mistakes.

If you have multiple outlets protected by a GFI outlet, plug the device, or 
a lamp, into the other outlet(s) and push the teensy button.  It's easy to 
see if the thing is wired right.  The outlet tester will not tell you if 
the GFI outlet is wired to not protect the other outlets without you 
pushing the teensy button.

A GFI device works by comparing the currents in the Hot and Neutral wires. 
If the two currents are not the same, that means that some current is going 
elsewhere - through your body, for instance.  I understand that most GFI 
devices are meant to trip with about 5 milliamperes of current 
imbalance.  I also understand that in some situations, a properly operating 
GFI device will not protect you from some dangers, but I don't know much 
about that situation, yet.

Be safe,

Roy




- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing
13033 Downey Mill Road, Lovettsville, VA 20180
Phone 540-822-5911   Cell 301-928-7794
Work: Voice: 301-975-3254,  Fax: 301-975-6097
roy.morgan at nist.gov --