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jstover · Aug 6, 2006, 08:24 PM

I just moved into a new home that the builder said was pre-wired for ceiling fans. I bought the first fan and light combination, but when I popped the ceiling junction box cover off and measured AC voltage between red and white or red and copper with the switch on, I only found 46 VAC. I measured 0 volts with the switch off.

The nearest wall outlet measures 122 VAC with the same meter. Since I don't know what is involved with a ceiling fan pre-wire, I don't know if I should be getting full house voltage at each pair of test points mentioned, or if these measurements are normal for ceiling fan wiring. Any suggestions?

ceilingfanrepair · Aug 7, 2006, 12:03 AM

Ceiling fans are 120vAC. What sort of switch is controlling the potential fan?

jstover · Aug 7, 2006, 11:12 AM

Unfortunately, I discovered my error too late. I should have checked voltage between white and black. When I first opened the ceiling cover plate, I found the copper wire stuck into the same wire nut as the black, so I assumed that the "ceiling fan pre-wire" used black as ground, as in electronics. After I took my voltage measurements, I turned off the wall switch, but I noticed that the copper wire was loose in the wire nut, so I made sure it was secured in there good and tight with the black one before quitting for the day.

This morning, when I came into the office, I mistakenly turned on the wrong switch, heard an explosive crackle (and I swear, a clanking noise) from the ceiling, and reflexively turned it off. I knew immediately that I should not have made an assumption about the copper and black wires. The black had been cut straight across at the end, so I think that the initial grounding blew apart the contact between the two wires, because the breaker did not trip, as far as I know. The insulation at the end of the black wire is charred, but it seems to be OK from about 2 inches back. I'll just follow the fan installation instructions for now, but will post again if I do something else exciting.

ceilingfanrepair · Aug 7, 2006, 02:14 PM

Black and red are hot, white is neutral, ground is ground. Connecting black and ground caused a dead short, as I am sure you know by now.

Your initial measure between red and white should have yielded 120vAC.

Let us know how it works out.