Issue with 240 voltage

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Old 07-28-19, 07:23 PM
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Issue with 240 voltage

I have a 240v outlet that was put in professionally a few months ago for my Tesla. On a few occasions, charging has failed and I can't determine the problem. I measured the voltages of the two legs to the 240v outlet. One was 131v and the other was 105v. Is this a problem, or does it not matter as long as it adds up to roughly 240v? I'm thinking this may be the issue that's causing my charging to fail.
 
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Old 07-28-19, 07:28 PM
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It can be an issue if the charging system is a 4 wire (hot, hot, neutral, ground) or if the charging system uses the ground for power.

If it is a 4 wire, that kind of imbalance can be caused by a loose neutral. I suggest going around the house and check your other 240 volt receptacles (Oven, range, dryer, etc) and see if the issue is there as well. You may have a loose neutral at your electricial service.
 
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Old 07-28-19, 07:38 PM
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Those voltages indicate you have a failed neutral connection.
Do the same measurement at another 240 volt device like dryer or stove. This is potentially damaging to any electronics (TV, DVD, etc) in your house. Call the POCO first thing in the AM.
 
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Old 07-28-19, 07:51 PM
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I just remeasured the voltage and this time it was more nearly balanced. Would running 120v appliances like a dishwasher or microwave cause the voltage to drop to 105v or is the problem something else?
 
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Old 07-28-19, 10:01 PM
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With a bad neutral, voltate at 120 volt receptacles will keep changing with varying usage.

You should unplug all electronics including microwave ovens and also washing machines with digital controls.

Simple test, plug in a hair dryer at a double receptacle. Measure voltage at the other receptacle. Turn on the hair dryer. Measure voltage at the other receptacle again.

Also, if you see incandescent lights unusually and abnormally bright and bluish then you have a neutral problem.
 
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Old 07-29-19, 04:49 AM
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Is there an easy way to test whether the issue is mine or the power company's? We've had some strange things happen with our power service in the past.
 
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Old 07-29-19, 05:38 AM
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No easy way to test where the problem is unless can see a damaged connection by looking outside. I would just call them. They will tell you if the is theirs. If not then you can call an electrician.
 
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Old 07-29-19, 07:09 AM
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I agree that you should have the power company come out and inspect their side of the service. They will usually do this for free. When you call tell them you measured unequal voltages and they will know what that means.
 
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Old 07-29-19, 01:05 PM
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The power company came out and found a loose neutral wire on the pole. Thanks to everyone for helping me diagnose this problem.
 
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Old 08-02-19, 08:21 PM
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For those eavesdropping:

Measure voltage at several 120 volt receptacles in different rooms during a time you are experiencing the problem..

If you measure some with too high voltage, some with too low voltage and some with nearly 120 volts then the problem is yours.

If all receptacles are either somewhat too high or somewhat too low then the problem is in your panel or in the service entrance or in the power company equipment.
 
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Old 08-02-19, 08:34 PM
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The power company came out and found a loose neutral wire on the pole.
It's good you stopped by and asked for help.
Had that neutral gotten worse.... you could have lost a lot of sensitive equipment in your home.

I'm actually surprised that your neutral problem affected the Tesla charger as they are straight 240v and don't require a neutral.
 
 

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