Well one thing’s for sure. You’re definitely reading the Nightmare Installation stories with a watchful eye. The “Handle with Care” story in the last issue elicited the most responses of any story we’ve run to date.
Many of you questioned the facts presented in the story. Here are a sample of your comments:
• “How could the author have possibly read 240V on his meter? If one screw hit phase A and the other screw hit phase B, the result would be a phase-to-phase short circuit.”
• “There should never be more than 120V to ground in a home supplied with a 120/240V service.”
• “I believe that in order to read 240V from the handrail to the doorknob you need to one line to the handrail (L1) and another to the doorknob (L2).”
• “Cute story, but in my mind, nothing more than an ‘urban legend.’”
Still others questioned the electrician’s work practices.
• “I think Jon was misreading his meter.”
• “The article pointed out the need to test electrical circuits/problems with appropriate test equipment, not the human body.”
• “After he replaced the six inch screws, did he open up the wall and check the wires for damage?”
One of you even thought we were deliberately trying to trick each of you.
• “Nice try, or is this the trick article and I’ve just won a free trip to Italy for finding the problem?”
In an effort to help clear the air, we forwarded a couple of your responses on to the author and asked if he would be willing to provide a response. And he was gracious enough to do so.
Jon Murfitt's response:
By all rights this doesn't sound possible, BUT it is.
Let's start with the handrail. It was a piece of 1.25 rigid conduit that was buried and concreted into the ground. It was strapped to the 3 concrete steps up to the door. Thus making it grounded. Now this was obviously an older home with a 100A Federal Pacific panel. We all know that Federal panels don't trip very well when over-loaded or short circuited. When you connect phase A and phase B together it should either short out or act essentially as a heater (the later-depending on the resistance), but in this case I ASSUME it was acting like a heater. I didn't want to touch it with bare fingers to find out! (Side-note -- The customer said that his power bill was rather high for being a small home.) Now I am also assuming that there was knob & tube in that particular wall. It might have been an added circuit at a later time with NM-B type cable or cloth wiring. If it was an added circuit, for instance a 240V air conditioner (or a like appliance), the wires would have been right next to another in an NM-B cable. The screws might have also penetrated 2 different (separate) cables. I am not sure of the wiring in there. I didn't open up the wall to see.
Now the door was a wood frame door with a metal door knob. So with the striker being energized, the flow with carry through the metal workings of the knob and stop. That is until you continue the path to ground. If I would have taken a piece of wire and attached it to the knob & touched the other end to the handrail (being ground) it probably would have blown-up. I don't know, I didn't want to do that. In my mind this was like nothing I had ever seen before. The circuit should have tripped, but it didn't. Or the stricker plate should have burned up.
I have been an electrician for about 10 years. I am an Electrical Contractor in the State of California, and hold my Journeyman's license in Washington.