K & T and GFCI

Yesterdays house is mostly K & T, it is a 2 family, and the owner just recently installed GFCI outlets in several rooms.

When testing the device with the buttons, it tests properly, when using a tester, it obviousally shows no ground and will not test. I remember reading back at some point that a 2-prong system can have a GFCI and be wired to operate properly and will not trip if a tester is used. That appears to be the case here.

What I am trying to figure out is, if a normal 2-prong system has a 3-prong device installed without grounding it would be considered defective. Why would it not be the same case with a GFCI?

The owner (seller) indicated it was his understanding that in using the GFCI device (again which does properly test by the devices buttons) satisfied the code for a 3-prong non-grounded system.

Input please.

The GFCI receptacle should be labeled no equipment ground. The three prong receptacle should be labeled GFCI protected and no equipment ground.

**An ungrounded Outlet.**When three prong receptacles with open grounds are identified and a two-wire system is present, the NEC® currently allows the following methods to be used to resolve the problem:

  • Install an equipment ground. (recommended for high end equipment)
  • Provide GFCI protection for the receptacle (either at the receptacle or upstream of the receptacle) the receptacles are to be marked “no equipment ground”. This method does not provide an equipment ground.
    *]Replace the existing three-hole receptacle with a two-hole non-grounded receptacle.

Filling the ground holes with a hot glue gun or similar method is recogizied up here as an acceptable method.

One thing I mention to my clients is that when using GFCI’s without a ground conductor, a surge protector will no longer offer much surge protection.

A surge protector sinks the majority of the surge to the ground conductor. So I alway recommend computer equipment to be grounded.

Also, do not use a GFCI on a refrigerator or freezer because they tend to trip the day after you leave on a two-week vacation.