Voltage swing, lights dim on 200 amp service.


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Old 01-14-15, 06:43 PM
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Voltage swing, lights dim on 200 amp service.

Hey everyone, I havent checked in for a while because we've been very busy enjoying our new house! Again a huge thanks to those who answered the questions I had while building. I really appreciate it.

Now that we are settled in I am starting to get pissed at a gremlin...

When our electric dryer starts, the 5 non LED bulbs we have in the house dim, any fan we have running slows down and my vent hood if its running gets sluggish.

I measured both phases vMin and vMax while the house was very quite and not much was running.
1st phase sat at a fairly stable 125V, 2nd phase was a stable 114V.
I ran the drier and the 1st phase measured 125V Max, 110V Min. The 2nd phase measured 120V Max and 112V Min.

I questioned gauge of wire the PoCo used when they buried the service to the house. It was no larger than O, or OO Al. Its a 200 amp service... Service comes from a streetlight on the corner of my lot roughly 100' away. The service TO the light was never upgraded when they tapped off it to feed my house.

Is this voltage drop "normal"?

Wes
 
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Old 01-14-15, 07:28 PM
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It sounds more like a bad neutral connection to me. I'd call the power company emergency service number and get a trouble truck out there pronto! They have trucks on the street 24/7 for issues like this.
 
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Old 01-14-15, 07:34 PM
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Could the Neutral problem be on my side?
 
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Old 01-14-15, 07:54 PM
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Normal power... A leg 125v and B leg 114v

I ran the dryer and... the A leg went from 125v to 110v and the B leg went from 120v to112v

That doesn't appear to be neutral problem.... more of a sag...... or an undersized neutral and sag. Usually the legs are fairly even.

No matter the exact problem.... the power company should check your electrical system out.
 

Last edited by PJmax; 01-15-15 at 08:27 AM. Reason: typo
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Old 01-14-15, 08:15 PM
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Service comes from a streetlight on the corner of my lot roughly 100' away. The service TO the light was never upgraded when they tapped off it to feed my house.

I presume there is a PoCo transformer on the streetlight pole? When I read this, my first thought was that they tied your home into the street lighting circuit, which normally is a light-duty circuit just for street lighting. Surely, there is a distribution transformer on that pole (but stranger things have happened especially with small municipal electric utility companies!) Just wanted to clarify this for my own curiousity!
 
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Old 01-15-15, 03:25 AM
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Thanks for the input.
There is no transformer on the street light pole. The street light pole is fed aerial from another pole 150' away with no transformer
I'll have them come out today to talk things over. I'll verify my neutrals are all tight in the panel as well.
 
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Old 01-15-15, 06:54 AM
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The voltage on the one leg differs more than I would expect from the other leg. Something does not sound correct.
 
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Old 01-15-15, 07:23 AM
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This has to do with the condition of the lines and the usage by other homes sharing the same pole transformer.l

A neutral problem is not revealed by turning on a 240 volt appliance.

A neutral problem is characterized by one leg voltage rising while the other leg voltage falls.
 

Last edited by pcboss; 01-15-15 at 08:25 AM. Reason: spelling
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Old 01-15-15, 08:34 AM
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A dryer is not strictly a 240v appliance. It's a 120/240v appliance. I can tell from his voltage measurements that the dryer motor is on the A leg as its sag was worse due to the 120v motor.

I ran the dryer and...
the A leg went from 125v to 110v = 15v
and the B leg went from 120v to112v = 8v
 
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Old 01-15-15, 09:34 AM
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What was the voltage between the A and B legs?seems odd not to have a pole Transformer closer than that,how many other homes are on that street?
Geo
 
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Old 01-15-15, 09:38 AM
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Technical note: You wrote "first phase" and "second phase" but it is single phase. Just leg A and Leg B of a split phase supply.

Just curious:
There is no transformer on the street light pole. The street light pole is fed aerial from another pole 150' away with no transformer
And where does that get its power?
 
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Old 01-15-15, 07:03 PM
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I questioned gauge of wire the PoCo used when they buried the service to the house. It was no larger than O, or OO Al. Its a 200 amp service
The power company is not bound by the NEC. They have their own rules on wire sizes and transformer installs. I do agree you should have them out to check things on their end. On your end, make sure all your wire connections are good and tight, and any aluminum wire has anti-oxidation paste.
 
 

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