I am a home inspector and I have a question regarding the proper way to test a GFCI receptacle. I recently inspected a 50 plus year old home with a two wire system. In the master bathroom, I found two GFCI’s next to the sink. When I pushed the test button of either one, it would trip as one would expect. However, when I pluged in my circuit analyser with GFCI tripper, neither outlet would trip. Is this because it is a two wire system? Is this GFCI working properly? I would appreciate feedback from any qualified electrician who happens to read this. It is my policy to always make absolutely sure that I am giving my clients reliable information. In this case, if the GFCI is in fact not working, then someone could be seriously injured as a result of my negligence. Thanks in advance for your reply.
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Replies
Yes, the problem is that you have a 2 wire system and "simiple" external tester are not affective.
A GFCI has a torrid transformer that have both the hot and neutral wire wrapped around it in such away as the current cancels. But if there is a current embalance, as would be caused by a ground fault, then the transformer generates a signal which cause it to trip.
External GFCI testers apply a resistor from the hot lead to the ground soa that part of the current is shunted off, just like if a person touch a defective appliance and a grounded sink at the same time. But since you don't have a ground wire it won't work.
The internal test button work by connecting resistor from the hot lead AFTER it goes through the transformer to the neutral lead BEFORE ot goes through the transformer.
Using GFCI's on 2 wire circuit are code approved and infact one of the prescribed methods for added "ground style" outlets to 2 wire circuits. However, the code does require them to be labeled as such. And the labels come with the GFCI's, but are never used.
Thanks for your reply Bill. I will, unless I hear otherwise from you, that the GFCI on a two wire system is functioning properly if it trips when I push the button. I had already suspected that those little exteral testers only worked when the GFCI was grounded. Thanks again. Inspector.
My daughter and son-in-law recrently bought a house and the home inspector told them that they had a problem in the kitchen because they had a gfci on one side of the sink and did not have one on the other. I went down to help move and was prepared to install one. Guess what, it was down stream and properly protected from the other one. He did not say anything about the second bath that did not have a visible gfci. It was downstream of the one in the master bath at the other end of the house on a 15amp circuit shared with the outside outlets. This was in a good sized city in Ga. and the house was a fair quality house built in 1995.
By the way why the monster sized type? Your font is a little large for comfortable reading.
I would recommend that you check out a few simple wiring books if not reading the code sections about such items. The code check series has some wire-bound laminated books on electrical and plumbing that might be good for you.
Cheers!
passionate love affairs are "torrid"
transformers that are shaped like a doughnut are "torroid"
:o)
Norm
Can't some one have a passionate love affair over doughnuts?
How do you think I got the doughnut around my waist?If everything seems to be going well, you've obviously overlooked something.
Sorry about the large type, but someone told me that Fine Homebuilding readers were a bunch of old farts so I thought I had better use the large type. Just kidding. The inspector was not properly trained, and failed to realize that GFCI's are often wired in the way you describe. I should have tested all of the outlets in the bathroom and kitchen. A lot of licensed home inspectors are in the business only because it is an easy way to make money, but sooner or later, their incompetence will catch up with them. Inspector
A lot of licensed home inspectors are in the business only because it is an easy way to make money,
Huh? After 2200 or so inspections is still doesn't seem like an easy way to make money to me!
It's a great job, but easy money?!?_______________________
10 .... I have laid the foundation like an expert builder. Now others are building on it. But whoever is building on this foundation must be very careful.
11 For no one can lay any other foundation than the one we already have--Jesus Christ.
1 Corinthians 3:10-11
Dear Bob, It's like anything else in life. It's only easy if you don't do a proper job. I have been a carpenter for 25 years, and I really care about what I am doing, and I am always amazed at how hard I work at it even after all these years. Now that I am a home inspector, I apply the same principles to my work as always. I care enough to do the best I can, and I absolutely refuse to cut corners, period. I guess it's like the golden rule. I don't like it when somebody does a crappy job on my house, so I am not going to do a crappy job on theirs. Doing good work is it's own reward, and it makes this world a better place. Thanks for your reply. Inspector
Ahhh. The appearance of easy money.
Let's do the math: 250 x 3 x 5 and lets take a month's vacation x 48. $180,000! Where's that yacht catalogue?
Wow! And all I need is a flashlight and business card!
Someone at ASHI did a calculation awhile ago and figured for the average inspector it costs about $120 overhead to ring the doorbell. So 260 / 8 = $32.50/hr.
And good luck doing 3 x 5 (or even 2 x 5) year round.
_______________________
10 .... I have laid the foundation like an expert builder. Now others are building on it. But whoever is building on this foundation must be very careful.
11 For no one can lay any other foundation than the one we already have--Jesus Christ.
1 Corinthians 3:10-11
"Wow! And all I need is a flashlight and business card!"
Wow, is really that easy.
You don't even need a pen and report form!
Of course you could just give verbal reports. Keeps down the overhead and you don't have worry about any pesty law suites. After the house falls down that day after you inspected it and all you have to do is say the client misunderstood what you where saying. <VBG>
It is possible that the GFCI is wired wrong.
The test button tests the internal GFCI circuit. Your tester tests the outlet.
If the power is connected to the "output" side of the GFCI the button will trip the GFCI, but your tester will not.
It does not matter if the GFCI is wired correctly or not.
This is a TWO WIRE circuit. Without a ground connection the external tester won't function.
Bill, I think you are correct. An external tester will not trip a GFCI on a two wire system, because there is no ground. The tester will read "open ground", and the device will not trip. If you read the fine print on one of these plug-in circuit testers with a GFCI trip button, it will tell you that it will not work when a ground is not present. As you explained before, the GFCI will still do it's job as long as it is wired correctly. The assumption is that if the button on the device trips it, it is working properly. thanks again for your very helpful input. Inspector.
It is still possible that the GFCI is wired wrong.
How do I know? Because I have found them apparently non-functional but only wired wrong when using my tester.
"How do I know? Because I have found them apparently non-functional but only wired wrong when using my tester."
I don't know what you did or exactly what the circumstances where.
But for a TWO WIRE system there is no ground and there is no way for the tester to draw a fault current to test the unit. It will not trip using the tester regardless of it was wired correctly or not.
What you can see is tht if you use the test button on the GFCI and it trips then the tester might indicate that you still have power.
Also without the ground you can't tell if the polarity is reversed or not.
If you want some "real testing" you can get ome of the grounding adapters with the tab that is suppose to be held down with the coverplate screw on a grounded box. Connect a wire to that tab and then run it to a ground. Then plug the tester into the adapter.
BTW, some of the new GFCI's have led's and/or the won't reset if wired backwards.
If the power is connected to the "output" side of the GFCI the button will trip the GFCI, but your tester will not.
My experience has been that if the power is connected to the output side neither the GFI test button nor the GFI tester will disrupt the power. The GFI button will pop, but if you have a tester installed it will still show power coming from the receptacle._______________________
10 .... I have laid the foundation like an expert builder. Now others are building on it. But whoever is building on this foundation must be very careful.
11 For no one can lay any other foundation than the one we already have--Jesus Christ.
1 Corinthians 3:10-11