220V Ceiling Fan?

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Old 04-18-03, 09:24 PM
jpsolo
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220V Ceiling Fan?

There are two identical ceiling fans in my den and one of them failed a few days ago. It's at least 7-8 years old (it was in the house when I bought it) and has worked flawlessly until a couple of days ago when the motor locked up. When I was searching for the breaker, I was surprised to find that after turning off ALL of the 110V breakers in the panel, the second fan was still running (Ibeileve they are both on the same circuit). I then turned off what I think is a 240V breaker (double handle joining two single breakers) and the fan stopped. I then turned the breaker back on and checked the voltage at the failed fan ceiling box and was startled to find it was about 240V (old Radio Shack analog VOM). I looked at the failed fan motor and it is marked 110V. I'm sure if it is really a 110V motor and it was connected to a 240V line it wouldn't have lasted more than a few minutes?? I am assuming that sometime in the past, an electrician has connected to one hot wire and the neutral in a 240V circuit to give only 110V. If this is the case, why would I see 240V at the ceiling box?
 
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Old 04-19-03, 06:36 AM
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This is a multiwire circuit, sometimes called a shared-neutral circuit. As long as the fan was connected to one hot and the neutral, it would be running on 120 volts, even though there is 240 volts present in the ceiling. But you are correct, if the fan had been connected to 240 volts, it would have died quickly.
 
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Old 04-19-03, 03:23 PM
jpsolo
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Thanks

John - Thanks for the reply. I gathered a little more data. There is a single wall switch that turns off both of the fans. The wiring at the ceiling box (of the failed fan) is a typical no. 14 romex with a two insulated wires (black and white) and a bare ground. With the breaker on and the switch in the "on" position (up), I read the following voltages: white - bare ground = 40V / black - bare ground = 90V / black - white = 110V.

With the breaker on and the switch in the "off" position (down), I read the following voltages: white - bare ground = 110V / black - bare ground = 240V / white - black = 240V.

Unfortunately, I didn't pay attention to how the black and white wires were connected to the fan wires. (I guess I can look at the other fan to see how it's wired). From this, it seems to me that when the wall switch is in the "off" postion, the fan will be seeing 240V if it is wired black/black and white/white.

Does this seem like what you described in your first reply? If so, is this type of connection acceptable in the NEC?
 
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Old 04-19-03, 03:45 PM
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Your measurements don't make any sense to me. With both the breaker and switch on, you got
  • B-W: 240
  • B-G: 240
  • W-G: 110
This isn't possible with single-phase power!

Is this just a regular home, or is this maybe a factory converted to a home? Any chance your voltmeter is nuts? Or perhaps you?
 
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Old 04-19-03, 06:20 PM
jpsolo
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Voltage Readings

No, it's a regular 25 year old residence in a subdivision. The readings I got with both the breaker on and the switch in the "on" position were:

White - Bare Ground = 40 V
Black - Bare Ground = 90V
Black - White = 110V

The higher readings were taken with the breaker on and the switch in the "off" position.
 
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Old 04-19-03, 06:40 PM
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Sorry. I misread. I thought the readings I posted were with the switch on. Forget the readings you took with the switch off. They don't mean anything.

I don't think you have a good ground. I also think your voltmeter may be suspect. Analog voltmeters are not usually subject to being fooled by phantom voltage, but it seems that perhaps yours is.

You still have a multiwire circuit. Although I cannot yet explain everything you are seeing, I think you can just buy a new fan and hook it up.

If you'd like to resolve all the symptoms just as an academic exercise, I'm willing to work with you on that. Try this. Buy a simple $2 bare bulb fixture and install it on the black and white wires. See if it works. Then just an an experiment, connect it to the black and bare instead. This is a dangerous installation and should not be left in place for more than the few minutes it takes to try it. See if the bulb works and whether or not it is as bright as it was when connected to the black and bare.
 

Last edited by John Nelson; 04-19-03 at 07:38 PM.
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