One leg drops 6 volts with a hot plate?

[madosta]

So my buddy has a house and is irked by the lights dimming when he's out working in the garage (or so his wife says). I didn't believe him for a while, because we all know most women are doing nothing while in the house when they should be cleaning.

He has some 10-3 romex buried out to his garage and 100 amp service from the meter can to a disconnect (and grounded) then to his panel (Cu) maybe 35 ft.

He's upgrading his garage properly either from the meter can or his house panel with THWN... lol

So I went over, took the panel off and we start testing with a high draw 120v appliance since I think it's a neutral issue. With the hot plate on one leg when it turns on, you can see a flicker and voltage goes from 118 to 112 sometimes up to 120 and down to 116/114. On the other leg, there is not really a noticeable difference and the meter stays around 124v.

One leg is usually higher than the other by 4-6v.

AC running on both legs no noticeable impact.

The mast is bent from a tree falling on it so I was thinking the neutral was pulled from the meter can, but he is saying he has always had these problems before the tree fell.

Is it an Edison issue with the neutral to the transformer? Well, from the panel to the transformer, I realize any of the connections could be muckered up...

 

[theoldwizard1]

You have to run the same test at "meter can". If you don't want to break the seal, probe the voltage at the feed into the load center in the house and run the same test.

In the end, your PoCo is not likely to do anything as 4-6V difference is well within the normal range.

 

[MTW]

If you have a bad neutral connection on the service, that should put some voltage on the ground wire to the water service.
A word of CAUTION HERE. The ground could be carrying all of the current from the home if the neutral is disconnected on the pole. So first loosen the ground wire to the water pipe and observe for sparks while moving it. Do not disconnect it if you see any sparks as you will send high voltage (240V) to all of the circuits if you do.

If that checks OK then remove the ground wire and check the system voltage again. If the voltage remains the same then the neutral is probably good. Then my guess is you may have a bad connection on the leg that is reading low.

I would cut the seal on the meter can and visually inspect the connections in there. Water damage from a leaking service head will corrode the aluminum parts and the riveted connections will not pass current after becoming corroded. If that is the case you will need an electrician, as Edison is not responsible for the meter can, the owner is.

 

[Jarcese]

Yes, the POCO will come out and do something about a 4-6 volt drop because it's an abnormal condition. If the voltage was 116/116 they will not do anything because that is normal, but 124/116 is obviously bad and is dangerous if you have unbalanced load.

Yeah it could be anything from the main lugs in your panel to the bushings on the transformer.. normally that's around 6 neutral connections to check, but it should be easy for them to figure out.

The ground is not going to carry any load unless it's bonded to water pipe that is bonded somewhere else along the pipe to the neutral. There may be voltage, but not load if it can't return to the source. Don't loosen your main ground connection. You already know there is a bad neutral and it wouldn't the drop/raise if it were bonded somewhere else. You wouldn't notice a problem if it was bonded to the pipe and then the neutral, you would only notice when you break the bond. Since you already have a nocticable problem, don't waste time/create another problem removing ground bonds.

I just re-read the OP after I started typing, but you need to check line to line voltage. If it's 248 and one side is staying at 124 and the other is going to 114, then it's not your neutral. If it's 240 and you're getting 124/116, then it is your neutral.

 

[Jarcese]

Just wanted to add that I work for the POCO as a troubleshooter and we will usually come out within an hour and fix the problem right away. If you're not familiar enough with electrical, by the time someone replied to the OP you could have had the problem fixed. Most guys will even go inside the house and show you where the problem is if it's not on our side, we can't fix inside stuff for liability reasons though. Save yourself possible damage to equipment by calling right away and not waiting. Plus you will be kicking yourself when an electrician comes out and takes $100 from you and tells you to call the POCO I know we get a lot of ****, but aside from major storms and service upgrades, we show up quickly for emergency calls.

Little bit of a rant, but calling your POCO is the fastest, cheapest, and safest way to go when you have an electrical problem unless you're familiar with electrical.

 

[Warrenator]

I had this same problem, our lights would dim when some big draw kicked on. Thought it was normal, then I was out in the yard and noticed our lights went dim when the NEIGHBOR's pool pump turned on. Called SDG&E (poco) and they came out and put a recording meter on it for a few days, showed me the printout with all the spikes and valleys, ended up replacing our transformer on the pole out front that fed 4 houses. No Charge.

 

[mechanicworkman]

Sounds similar to what happened at my house. I had a voltage difference of around 6 volts from one leg to the other. I was experiencing dimming lights and other similar problems. Another member recommended talking power company to come check neutral on pole first before calling an electrician. I decided to call electrician first long story short 8 hrs later stumped electrician finally called power company. Loose neutral it was!


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