Was asked today, What is the difference between GFI and GFCI? I gave an answer, that it was the same thing. But after thinking about it, I don’t know that for a fact. I’ve just seen them used interchangeably for so long that I assume they are one in the same.

Are they two physically different things, or are they the same?

Most people use it interchangeably…the main difference is them putting the “C” (circuit) in there… which can be vague at times. Putting a GFI on a receptacle does protect the person from electrocution at that receptacle…but it may not protect it down the line depending on how it is wired or the system itself… which is why it is vague… but that is being technical.



They are the same thing.

The gfi may be older lingo for receptacle usage.

I agree they are the same thing…

Newbie question…what’s the best tester one would recommend?

The only test recognized by the NEC is operating the buttons on the device, itself. If they trip the circuit, but your tester doesn’t, it is not (officially) the receptacle or breaker that is defective.

I use the button on the device when I’m at the device itself and use the three light tester to check downstream outlets.

My tester will not test a GFCI if there is an open ground wire, which is not actually required to operate the GFCI. I would agree, and have myself come across several GFCI’s that operated with the buttons and not the tester.

It is better to understand that the real thing to be thinking about that GFCI or GFI come in Class A or B types. The mA levels of activation (protection) vary from 4-6mA and up for Class A and 20 mA to 30ma ( depending on the manuacturer ) for Class B types. It is important to remember that the Class A will save a life while the Class B will not…Class B are for equipment protection only.

Many engineers call the GFCI the Class A and the GFI the Class B…but I believe it is just more important to know which Class than the actual verbiage of the device’s name.

Also another tidbit…when we look at some larger electrical equipment that has built in GFI prtection…it is not really circuit protection as you would see in the term GFCI…it is not really any circuit protection at all in these types of setups…so it would truly be only GFI protection and not GFCI protection.

So while we can use the jargon as we feel fit…and I do it all the time for convience. It is also nice to know that in real world their are differences in the two terms.

Is it correct (in laymens terms) to think of GFI protecting only the receptacle, where GFCI also protects the down stream receptacles as well?

Ahhh…well if you are asking my opinion then I don’t believe it really translates into that. I believe the correct verbiage should be GFCI for the protection aspect of the 4-6mA and above protection and use GFI for the 20mA and up protection for equipment and then use GFP for the requirement for 230.95 150V to ground and not exceeding 600V type of protection on service equipment where applicable.

I would not have a problem with someone calling a GFCI a GFI as well…call me me but depending on the application, someone knowing what you are talking about will know which you are talking about so I kinda don’t worry about the symantics of it but some will disagree ( but I dont let those people bother me…I beat to my own drum )

With that said I don’t think your view of it is too off base…in fact the more I say it your way the more I like it…;)… The act however of a single GFCI device not protecting any devices down stream would still make it a GFCI Device in the eyes of the NEC regardless.

**[FONT=Times New Roman][size=2]Ground-Fault Circuit Interrupter (GFCI). **[/size][/FONT][FONT=Times New Roman][size=2]A device intended
for the protection of personnel that functions to deenergize
a circuit or portion thereof within an established
period of time when a current to ground exceeds the values
established for a Class A device.

I think Paul is saying that GFI protection while protecting equiment is not equivalent to GFCI protection.

GFCI is people protection.

GFI is equipment protection and trips and a much higher level than a GFCI.

yeah…Im kinda saying that but I found it is easier to waddle through the muck if you just learn to call them GFCI Class A Devices when you want to deal with the devices that protect human life…:wink:


Here’s a followup question. How do you tell the difference between a Class A device that is a GFCI that protects people, and a GFI that only protects equipment?

Since I’ve only heard them used interchangeably, I’m not sure I could identify one from another. (of course I can identify a 15 amp receptacle vs a 20 amp).

To be honest with you Mark I don’t believe they make Class B Devices anymore. I have not seen any around. Usually it would give the class on the device itself to help you determine but in a conversation i had with a rep a while back I don’t believe they make the Class B ones anymore…but then again I could be wrong.

It would appear Article 426 of the NEC would still call for their intent but alas I again have no idea if they make them anymore…my GUT tells me they do…

**[FONT=Times New Roman][size=2]426.28 Equipment Protection. **[/size][/FONT][FONT=Times New Roman][size=2]Ground-fault protection of
equipment shall be provided for fixed outdoor electric deicing
and snow-melting equipment, except for equipment
that employs mineral-insulated, metal-sheathed cable embedded
in a noncombustible medium.