GFCI Questions To the Editor: Regarding "Safe Wiring With GFCIs," by Rex Cauldwell (12/92): The last paragraph under the heading "Incorrect Wiring of GFCIs" states that "the incorrect hookup would be immediately apparent if the test button doesn't trip the device." Unfortunately, this is untrue. The test button is valid only if the device is wired correctly regarding load and line. I first suspected this after testing many GFCI receptacles with a plugin tester and finding that if load and line connections are reversed, the GFCI will only trip for ground faults downstream from the device, and not at the device itself. The best advice to your readers is not to rely on the built-in test button for verifying correct installation,