When testing an exterior outlet yesterday with a 3-light tester, I was shocked when I pushed the GFCI button. My other hand (the one that was “buzzed”) was on the metal siding and/or exterior metal cover. I know its obviously not right, but can someone advise on why/how this happened?
I had the same thing happen. I tested the receptacle while leaning on the air conditioner. Just wrote it up and moved on. Electrician was called and fixed it.
That will occur if/when the metal cover is not grounded. Remember, the tester is shunting 10-15 ma to ground when the test button is pressed. If the ground, i.e. on the cover, j-box, conduit, etc is not present downstream then your body will provide a path (assuming you are somewhat grounded) and a mild shock will occur.
Here is one to add to the files!
I tested this one on the Garage and got shocked when I by accident touched the metal casing. It also was not secured as it looks like someone hit the siding below the outlet.
It (was) common to ground metal siding. Google it. This will get you started… http://forums.mikeholt.com/showthread.php?t=139270
This was a lesson in how to NOT test a GFCI device.
The little plug in tester DOES NOT GIVE A LEVEL OF AMPERAGE it took to open the device so the test is worthless.
THE ONLY APPROVED METHOD TO TEST THE DEVICE IS WITH THE TEST BUTTON ON THE DEVICE.
Testing with the plug in tester is good** ONLY** for locating the GFCI device not for testing one.