[jercleve]

I've read some of the other questions on this site related to open neutrals as I was searching the web on my particular "issue." I am not certain I have an open neutral or I'm just being a hypochondriac.

This is what I am seeing:

The lights in any room in the house dim for a split second when powering up virtually any other device in the house. Ive seen this with the electron hogs like the washer & dryer, but I also see this with the PC, TV, guitar amps, and other smaller current users. I have also seen this when there is low total electrical use in the home. For example, if there is nothing else powered on in the house except one light, and I turn on something (like the TV) that one light will dim for half a second and return to proper illumination.

If this was a dim on the same circuit, it would be one thing and potentially expected behavior, but when the refrigerator kicking in dims lights in the bedroom, it seems like something is wrong.

I have also had a power supply in my PC die as well. It happened a few months ago. That may not be related, but I'm thinking that if I have an open neutral on the main, then it could compromise the stability of my current and cause failures on electronic equipment. Maybe?

Oh, I've lived in this house for a year, and it has always done this. This house is 10 years old.

What do you think? Open neutral? Ground issue? Not much juice from the utility? Or is it nothing?

[KISS]

Yes, the power flucuations could have taken out the PC power supply.

Yes, you need to get it fixed.

It may not be an open neutral, but it's likely a bad connection somewhere. It could be overhead or underground before it hits your meter or it could be in your panel box. It could even be a bad main breaker.

[donf]

Lets start by the Utility company. What is the rated amperage of the service being delivered to your house?

Are you on lateral (below ground) or overhead service? Do you have a Volt/Ohm meter and know how to use it?

Have you contacted your Utility company? If there is a broken cable from the Utilities transformer to your home,then that could easily cause the type problems you are seeing.

If the failure can be isolated to a single circuit then that's the one you would need to check. When it's a full failure as you are describing, I normally suspect, the Input service, owned by the Utility company or the main panel box having corroded hot legs.

[Stratmando]

If when refrigerator kicked in, and lights went bright would be an indication of open neutral.
Besides the Breakers and connections, you also need to check the Buss the breaker plugs onto, and the breaker itself(where it contacts on the Buss)or bad breaker.

[jercleve]

I have a 200 amp service. It is underground. I have access to some Flukes and know, generally, how to use them. I work in the computer engineering field, so my experience with volt/ohm meters is on electronics, not household wiring.

I did some poking around last night with the breaker box. It seems that the previous owners did some alterations since the last inspection as the labels are not entirely accurate.

For example, closing the circuit labeled "garage" kills the garage door opener (plug on ceiling), but not the garage lights and not all the plugs in the garage. The garage is on the front side of the house, but this circuit also goes to the 3 outside motion/flood lights on the opposite side of the house. I find that strange.

So I think I should take the time to map the circuits so I know which appliances, lights, and plugs are on which circuits.

It also looks like the previous owner added some circuits that are either 220 or some higher amperage 110. The plugs are not the typical 3 prong plug /w a parallel hot/return and a ground. See below:

Not this: | | but this: | --



I don't know if that's a 220 plug or like a 30 amp 110.

I think I will find that the den and bedrooms, as well as the living room, each have a 15 amp circuit; where each rooms circuit has both lights and plugs together. This is because when I power up the PC or guitar amp, only the den lights dim - that's the same room so likely the same circuit. The same goes for the TV and the living room.

But the question remains, when all other devices on a circuit are off except a single light bulb, should powering up something like a TV, PC, or guitar amp dim the lights? And I still get global dimming when the dryer kicks on. I know the dryer is on its own circuit, 220/30a I believe.

So I think measuring current is a logical step.

Perhaps if the utility is not supplying adequate current to my home, our neighbors may be seeing similar behavior in their homes. So talking to them may be enlightening.

Is measuring the current coming to my meter something that I can do myself, or is that a service that the utility company should provide?

[Stratmando]

You can measure voltage provided by Utility, and Load of your house or breakers with an ampprobe. Clamps around wire and will show current being drawn.
With your meter, measure voltage through breaker contacts. The worse the connection, the higher the voltage will be.

[donf]

Strat,

I do not understand your answer posted above. Not to mention the misuse of basic terms by the OP.

Why would you expect a broken or failing connection to show a Higher Voltage? I would expect just the opposite particularly if the connection is severed.

For example, we know that the utility company provides two 120 legs , one neutral and one ground. If one of the leads from the utility transformer is severed, there will be 0 (zero) volts on that leg, not 120.

Jercleve: You are scaring me. I to was an ET. For awhile. The rules of electricity don't change just because your now inside a box.

Since you have a Fluke meter, they should have an am meter section in addition to Ohms and AC/DC voltage.

Now-a-days there is no 220/110. Utilities supply 240/120. There in lies the difference in the receptacles in your home. However, a standard outlet is NEC approved for 110/120 VAC.

I also would start at the panel, however, I would test the two "Hot Line IN" at the top of the panel (depending on the panel installed). You should see 240 VAC. If you see less than that call the utility company. Another test would be to use the am meter section of the fluke and set the meter higher than 200 amps if you can. If there isn't a setting that high, don't make thee test, you will fry the meter.

Check the amperage available across the two hot lugs. If it below 200 AMPS, call the utility company and ask them to verify your service and give them the voltage and amperage readings as your reason why you believe their transfomer is causing the problem.

The utility company doe not allow anyone else to touch their wires so stay away. Call them tell them your symptoms and your test results and see if they will sen a tech to verify and fix the failure.

[labman]

Stratmando's post made good sense to me. He is one of the better people posting here. You should get near 0 voltage between the buss and screw or outgoing wire of the breaker when it is under a load. Some homeowners give DIY a bad name. Check all the breakers for a voltage. I would get all the branch circuits right before inviting the power company to visit.

Figure out what those outlets should be and make sure they have the right wire and breaker feeding them. If the wire is too small, change them out.

[Stratmando]

Quote"Strat, I do not understand your answer posted above."
Easiest way to explain is. If you go to a light switch, turn it on, both screws would be live, and if you measure voltage between the 2 screws it should be Zero volts, if you have a loose connection you will see voltage and if you Open the switch(That is a really bad connection) and may read 120 Volts, providing it is switching a load.
Above post I said Measure THROUGH breaker, not ACROSS breaker, On the main Breaker.
Can be confusing, I do appreciate questioning, instead of a red mark. Most of the people on this category seem anxious to help, without having to knock others.

[labman]

Oh, I forgot, give a beady eye to any breaker with 2 wires under the same screw.

[donf]

Strat,

That is true for a light switch because the terminals are in series with each other. Also, by definition, if you open the switch you will have to see 120 vac, because that is the electrical difference between the two points. There is no longer a one to one connection.
It certainly would not apply to the two hot poles on the main breaker. This not a test of two serial points. It's an additive test of two Parallel points. We are describing different test methodologies.

If you measure these, a good connection will yield 240 VAC. One lead severed would yield zero volts, so the cumulative voltage between the two leads would be 120, not 240.

If the connection of the lead was dirty, you might see a small amount of difference of around 10 to 30 VAC depending on the extra resistance added to that circuit.

To further isolate the failing lead, you would then measure between Neutral or Ground to see which lead is less than 120 VAC. Personally, I wouldn't go any further because I let the Utility company work their magic.

Comments of other member deleted

[KISS]

Look closely at the outlet your describing. It may have an sideways "T". @0 amp 120 V recepacles will accept 15 amp " | |" plugs. 20 amp receptacles however, SHOULD be wired with #12 wire and protected with a 20 AMP CB. I'll use the term should rather than MUST.

Typically, "The Pros" use the voltage drop across a lug/switch/breaker/relay contact under load to assess the quality of the connection. Without current flow, the test is meaning less.
Yes you need to use a low voltage AC scale to do this after using the high voltage scales.

Thus things you can check for is breakers being warm to the touch and/or discoloration. Discoloration is a sign of heat and sometimes caused by loose contacts. So you can check the voltage drop across the main lugs: probe on wire, probe on LUG. The voltages across breakers. A little more difficult: Between the coresponding main lug and the output terminal of the breaker.

Loose connections can be anywhere and therefore it is important to isolate your findings.

And, no. It's not normal for the lights to dim when you turn on a TV or a washer for that matter.

[Stratmando]

I like to do both test. Neither is Stupid or useless. You are correct, you would see 120, not 240. Don't get nervous, sweat makes a better conductor. I would also measure from each of the breakers to each lug. Not so much the 240 you will read from 1 line, but the near zero volts when measuring from same phase.
Because something doesn't make sense, doesn't mean it is wrong.

[pelle]

jercleve,
If you are OK working in the panel box and have a good volt meter, try the following.
Unplug any sensitive equipment computer TV etc..
Take volt readings at your main break phase to ground on both sides. Should be 120v each +/- a little.
Next put a cup of water in the microwave and turn it on high. If you have a neutral problem you will see a sway in voltage when you read phase to ground i.e.. 150 and 90 volts.
If this happens call the electric utility and have them check their equipment.
Post back with the results.
If not comfortable call your utility explain the problem and they should send a tech out for you, here this service is included in you utility bill.

[tkrussell]

An open neutral will cause some lights to dim, while others brighten. Since this is not reported, and only lights dimming seems to be the problem, then a hot line, or both, is most likely the cause.

My opinion is the problem, judging by the dimming of lights on ALL circuits as reported when the dryer starts, is a loose or corroded LINE connection, which can be in Main Breaker, or inside the meter socket, a defective underground cable, or a connection at the utility transformer.

Now on to some comments on previous answers:

Measuring voltage drop across a breaker, or any contact point should be done with a meter that can measure small amounts of voltage drop, in the Millivolt range. A standard meter usually does not go that low.

And, to do this test, you measure first across the Line of a contact to neutral, and then across the Load to neutral. A bad contact or connection will show the load side is lower volts by a few milliamps, and any reading exceeding 100 milliamps difference will indicate a contact that is questionable.

Jercleve, most of the contact points and connections that can be the problem are out of your reach, or otherwise inaccessible, such as inside the meter, transformer, or simply anything ahead of the Main Breaker.


Don, be careful suggesting to use the ammeter of a volt -ohm meter, as these are usually limited to the maximum of 10 (ten) amps. Only an AC clamp on Amprobe style meter can measure high amounts of current.

A utility company only delivers voltage, not amperage. It is what you do with the voltage is how they charge.

The utility provides three wires, two hot and one grounded (Neutral) conducotrs. They do not provide the ground.

Measuring the amp draw is irrelevant to the utility, that is what is being used, and will be limited to the rating of the service entrance.


What does testing across an open switch prove, other than a bad switch, if I see voltage. Any test across the switch will show volts due to reading through the load, and the resulting voltage drop due to measuring in series with the load.

The outlet described with the blade openings |- and a third for the ground, is a NEMA 6-20 20 amp 250 volt. Having these is not the cause of any problem. The previous owner may have had an machine of some sort.

My suggestion is to call in a good service electrician and the utility company to search out this problem.

[jercleve]

Yea, I think that is the answer I needed to hear. It doesn't seem like an open neutral now that I am better informed.

I'm a computer geek by trade, not an electrician, so I don't think poking around breaker boxes and meters is really something I need to be doing.

But the main thing I want to establish is if I: 1 - have a problem at all. And 2 - who to involve, utility or an electrician, or both.

Unfortunately, inspecting the electrical system is not part of the standard home inspection when a house is sold. Perhaps having a real electrician come take a peek is a worthwhile investment.

[tkrussell]

Outstanding!

Perhaps having a real electrician come take a peek is a worthwhile investment.

May I quote you, on a billboard?

[jercleve]

Quote me? Sure.

[ceilingfanrepair]

I've been reading this thread, and trying to make sense of it, particularly some of the answers. I was thinking, maybe the reason for the suggestions to measure amperage, was in case his usage is exceed his service? But what are the chances he has a 200 amp meter lying around?

TK gives sound advice as always. Heed him.

[Cobraguy]

Absolutely perfectly correct explanation of voltage drop Strat. A process EVERYONE should have in their "toolbox".