Electricity Monitoring

[Jody Boehs]

I have a friend that says his lights in his entire house flicker and dim a lot. I personally went to his house and made sure all connections were tight in his panel and meter can. He still is saying that didn't help. Is there a metering tool that I can attach to each phase and the neutral to monitor what's going on? Or does anyone have a better idea of what might be going wrong?

 

[Jraef]

I have a friend that says his lights in his entire house flicker and dim a lot. I personally went to his house and made sure all connections were tight in his panel and meter can. He still is saying that didn't help. Is there a metering tool that I can attach to each phase and the neutral to monitor what's going on? Or does anyone have a better idea of what might be going wrong?

Could also be a loose neutral somewhere other than in the panel. Depending on how the place was wired, all of the lights might be on one circuit, all strung together with one home run. Any loose or corroded neutral in that circuit would make the entire circuit flicker.

A recording power meter could be used to eliminate the possibility of it coming in from the PoCo side. They are expensive, but you can rent them.

Once you have (hopefully) eliminated the internal common issues, he can call the PoCo and they will often hook up a recording meter. Don't get too hopeful though, because the only time they will say there is an issue is if they can pin it on a neighbor connecting too big of a load or something, then make the neighbor fix their problem. If it's because their transformer is too small or they had a bad connection, they rarely admit it because then people want to be reimbursed. But they may quietly fix it.

 

[gar]

170214-0952 EST

Jody Boehs:

Do you have a digital voltmeter with a min-max capability, such as a Fluke 27? If so, then at the main panel and directly on the wires entering the panel, not the lug the wire goes into, use this function and monitor phase A to neutral for a short time during which flickering occurs, and record the min and max. Repeat for phase B to neutral, and last from neutral to a 10" or so long screwdriver inserted in the earth a short distance from the home. These measurements are close to where power enters the home and the responsibility of the power company.

Big changes, like 10 V, should not be expected unless there are large loads being switched on and off.

I use a 1500 W 120 V cheap space heater as an experimental test load. At my home If this load is connected phase A to neutral, then I see a drop of about 0.6 V on phase A to neutral, and an increase of about 0.3 V on phase B to neutral. The phase B to neutral increases because of the voltage drop on the neutral from the pole transformer to my main panel from phase A is 180 degrees out of phase with phase B..

Changing the experiment a little. At my pole transformer pole there is a ground rod at the pole directly connected to the transformer neutral. By inserting a screwdriver in the ground close to the ground rod I obtain a voltage reference point very close to that of actually connecting to the transformer neutral. Now my change of voltage measurements at the main panel relative to the pole transformer ground rod are 0.5 V and 0.1 V or less. This measurement virtually eliminates voltage drop on the power company neutral from pole to home and thus from the test. Could be helpful in spotting a poer company neutral problem.

Measurement of voltage drop on the power company neutral produced a change of 0.26 to 0.47 form 0.21 V resulting from the heater load change.Still using the pole ground rod reference point if I look at the voltage change on the output side of the 20 A QO breaker to the circuit that the heater load is connected to, then from the about 10 A load change the voltage change is 1 V. An apparent source resistance of 0.1 ohm.

.

 

[Jody Boehs]

Could also be a loose neutral somewhere other than in the panel. Depending on how the place was wired, all of the lights might be on one circuit, all strung together with one home run. Any loose or corroded neutral in that circuit would make the entire circuit flicker.

The house that he lives in is a 3 bed 2 bath house that's approximately 1800-1900 sq. ft. I think it is highly unlikely that ALL the lights are on one circuit. In fact I'm 95% sure they are not. If this is the case, then I have several loose connections in the attic. If the lifts are on different circuits, then what could be causing this.

 

[gar]

170414-1324 EST

Jody Boehs:

Get voltage measurements at the main panel when flickering is occurring. The reason to use a min-max capability is that its response time is much faster, fractional part of second, than is the meter display, seconds.

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[delongtrevor]

ohh great!
thanks for replies!

 

[LarryFine]

The house that he lives in is a 3 bed 2 bath house that's approximately 1800-1900 sq. ft. I think it is highly unlikely that ALL the lights are on one circuit. In fact I'm 95% sure they are not. If this is the case, then I have several loose connections in the attic. If the lifts are on different circuits, then what could be causing this.

Joey, a little flicker is normal, but rarely enough to complain about, so let's presume yours is abnormal. A few things:

1. Anything that affects more than one circuit must be either in, or ahead of, the panel. So, that's where you should be checking your voltages first.

2. There are two basic types of flicker:

a. Both line voltages drop, when a 240v load such as central A/C compressor starts.

b. One line voltage drops, other line voltage rises, when a 120v load such as a portable heater starts.

I suggest reading one line-to-neutral voltage while turning on a large 120v load, then reading the other line-to-neutral voltage while turning on the same 120v load in the same outlet. If one rises while the other drops, the issue is somewhere in the service neutral. Let us know how much each of the two voltages change, as well as line-to-line.

You should be able to see your voltages bounce around in sync with the flickering. As long as you see this happening in the panel, you can be sure the issues are on the incoming service conductors, and not within the house wiring. Common culprits are long and/or too-small service drops, poor connections in the meter base, corroded conductors and splices, etc.

Also, you can look for poor connections and breakers by looking for any voltage across a device, between two points that should be effectively tied together. A good fuse or breaker, or a switch that is 'on' should read as a short. If you put one voltmeter probe on one incoming hot, you should read 0.0v to one panel bus and every other breaker load terminal.

In other words, you should read 0v, 240v, 0v, 240v, etc. as you move down each side of the panel. Bottom line is that flicker is the result of voltage drop, which is the result of current through a pathway that has more resistance than it should, either by defect or less-than-ideal design, or something has changed since the service was first installed.

You need to determiner what and why.

 

[ptonsparky]

Years past we would have used incandescent test lamps and compared them to each other as loads are cycled.

Tightening a poor connection doesn’t always work. Examine the conductor and the setscrew if things don’t look right. Some of the older Al alloys just got flatter as you applied elbow grease.

 

[kwired]

You are likely to have more issues with cheap LED's and even some better quality LED's than you would have had with system in same condition and supplying incandescent lamps. I have some relatively cheap LED replacement lamps in some kitchen pendant lights in my house, they flicker in same rhythm as the washing machine agitation when the washer is running, washer is either an electronically driven motor I'm pretty sure, exact type I'm not certain, but it actually reverses the motor each agitation cycle vs older types that had a continuous running motor and mechanical methods of agitation action so I am certain it will put some spikes on the lines if you were to monitor voltage and current where old style washers would be more of a steady current other than at initial startup. Not on same circuit, have never checked to see if on same 120 volt supply line, definitely common to the main neutral though.

You also need to verify that incoming voltage is stable, you could have other customers on a common transformer and whenever a larger load starts in neighbor's house it effects voltage for everyone, especially if transformer is marginally sized to begin with. Long feeds and worse yet long feeds with multiple customers on them can be problematic here as well.

Though not as likely you can even have larger commercial/industrial loads nearby that effect primary voltage feeding your local distribution transformer.