A question for the electricians.

[endzone_dave]

I went to Home Depot to buy a GFCI (Ground Fault Circuit Interrupter) outlet for the house I'll be moving into. Since I don't know the size of the outlet yet, I thought I'd be covered by getting the 20A. But the lady working at HD said I need to get the right size, either 15A or 20A. Isn't the 20A simply the rating and if the 20A GFCI ending up on a 15A circuit all that would mean is that the 20A GFCI outlet would be able to handle anything the 15A circuit could feed into it?

This will be my first house so I know didley when it comes to this kind of stuff. Thanks!

[BG]

A given circuit in your house is going to be more or less on the same "wire". Meaning, each outlet in your basement is hooked to a 20 amp wire that is then fed to one 20 amp wire leading to the circuit breaker. However, it could be on a fifteen amp wire in your bathroom. It will vary room to room sometimes. Just go to the circuit breaker and find the room with your outlet. It will say, or pull the old outlet out and look at the wire. They are labeled most of the time.

[DaFunky1]

Originally posted by endzone_dave
I went to Home Depot to buy a GFCI (Ground Fault Circuit Interrupter) outlet for the house I'll be moving into. Since I don't know the size of the outlet yet, I thought I'd be covered by getting the 20A. But the lady working at HD said I need to get the right size, either 15A or 20A. Isn't the 20A simply the rating and if the 20A GFCI ending up on a 15A circuit all that would mean is that the 20A GFCI outlet would be able to handle anything the 15A circuit could feed into it?

In a word yes...

Wire size would be my biggest concern. The problem you run into with running a breaker larger than wire capacity is the wire then becomes your fuse. I was not a residential electrician, but I was an electrician for 9 years and dealt alot with wiring and GFCI's due to using alot of electrical devices in the rain. As a general rule of thumb, if the wire is 12 ga it is rated for 20 amps, if it is 14 ga you are looking at 15 amps. I believe most newer houses are 12 ga, but don't assume this.

Technically a GFCI is not your breaker as such for overloads (it will serve this purpose), that is usually relegated to a breaker in the panel itself, rather it is there to interupt a ground (or as the link in the article below states "neutral leakage") in a piece of equipment such as dropping the hair drier in the bath tub with someone in there... The GFCI will sense the current is going where it shouldn't be and "trip". Typically these are required near sinks and recepticals in wet or potentially wet areas.

To be on the safe side, check your local codes and make sure the wire gauge matches the breaker in the panel and the GFCI before installing.

Good instructions on installation (http://www.mindconnection.com/library/handyman/gfci.htm)

Peace

[Larry]

The rating on the GFI indicates the amperage at which it will "trip" due to over-current. The idea is that the breaker must be the weakest link in the circuit. (It must trip before the wire melts.)

The shape of the outlet is also different. There's a special plug (looks like the normal plug, but the vblade on the left is sideways) that's used on devices that draw more than 15A, so that they can only fit in 20A outlets. But, it's real unlikely that you'll be using such a device. (You see it on some air contitioners, for instance).

One question: are you looking for one of the GFIs that replace an existing wall socket, or one that replaces a breaker in the circuit panel? If you're replacing a breaker, then use the same rating as the breaker you're replacing. Replacing the breaker with a bigger one could be very bad. (If you're replacing a breaker, then you'll need to know who made your panel, 'cause different panels use different breakers.) (And be carefull: even with the main breaker off, there's still serious power a few places inside the panel.)

If you're replacing an outlet, then in theory, even if you use a bigger rating than the circuit, you're still safe, because you've still got a 15A breaker protecting the circuit (back at the panel.) It's perfectly legal to use a component that's rated higher than the breaker. (But, if you plug in something that has that special plug on it, then you're guaranteed to trip the breaker when you turn it on.)

Another tip: The GFI (if installed correctly: they're more complicated than a standard outlet) will protect anything plugged into it, and anything downstream from it. Where you install it will determine how much is protected.

Example: Your garage (or wherever) likely has one wire running from the panel to the room (to an outlet, or a switch, or a light fixture), and wires then run from box to box within the room. If you can figure out which boxes are the furthest upstream, then you can make the GFI protect more things.

(Of course, the simplest way to protect the whole circuit is to replace the breaker.)