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Is there a "name" for each Leg in AC voltage"

The typical U.S. home has 240v coming from the power pole, with a neutral, which is the center tap of the pole transformer. Thus there are two 120V supply lines. Each of these supply lines are called "Legs". This all makes sense, and with my electrical background I fully understand how it all works.

However, I have always wondered if there are names for each of these legs.

For example, lets say I want to balance the loads on my house, and swap some breakers from one leg to the other. Sure, this works, but lets say I want to describe what I did to someone. How do I identify on of the legs? Would they be referred to as LEFT and RIGHT, based on the location of the incoming main wires to where they are placed on the main breaker? That would work, except some panels have one on top and one below, this there is no left and right, but rather UP and DOWN. And you cant go by color codes because each main wire is black.

I'm asking this because I have been having a slight flicker in my house lights and this has been going on for at least a year. It's intermittent and random, but seems to be worse during wet weather. I metered it, and see a 5volt or less dip in voltage on an analog meter, during each flicker.

I used to work as an electrician, so I know what I'm doing, even though that was many years ago. I have taken apart all connections and made sure all wire nuts were tight and proper, swapped breakers in my panel, and more.... It's not just one light, it's several lights around the house. I just swapped one breaker (which is the one I notice this flicker the most often), to the other leg in my breaker panel. I have not seen any flickering since, but its a little early to say for sure since the problem has been random and intermittant.

Anyhow, if this swaps the flicker to the lights on the other 15A breaker, then I know the problem is on only one leg. That means it will be time to call the power company and have them inspect the connections at the transformer and my meter. But, how do I explain to them which leg is causing the problem? It cant be traced when the feed cable is twisted (triplex). And since my meter is about 100 ft away 0n a pole (farm wiring), I cant easily shut off the power and using the ohm scale on my meter to determine which leg is the cause (unless I run 100+ ft of wire from my meter leads between house and pole).

One other thing I did was unplug or shut off anything that would draw heavy current. Including the refrigerator, well pump, electric heating devices, pipe heating tape, and even shut off all power to my garage and barn. So, I'm convinced it's not a device, but rather a poor connection on the power company's side. I dont believe it's the overhead wires either, since I dont see any more flickering when it's windy. That pretty much leaves the meter housing ....

Reply to
boomer#6877250
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I guess the question I have is when you report this to the power company, do you think they are going to take your info as if it is gospel? I would just tell them your lights flicker a lot and you find it on just one leg when you move the lights. They are going to check everything they are willing to check and most likely find nothing. If they find a loose connection, great! But don't hold your breath.

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Rick
Reply to
rickman

"Fred" and "Sam"

Nope. They're interchangeable. They're commonly wired with red and black insulation but they're interchangeable (they should be consistent, however).

On the 240V, or on one 120V side, or high on one side and low on the other?

Reply to
krw

The usual names are L1, L2, N, ground.

Reply to
John Larkin

What Rick said, assuming that you've made sure that it's on the power company side of your main breaker.

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Tim Wescott 
Wescott Design Services 
http://www.wescottdesign.com
Reply to
Tim Wescott

For 3 phase: black, red, blue, white, green|bare|green-yellow L1, L2, L3, neutral, ground Ground is sometimes labeled PG (protective ground). L1 is sometimes called "hot" and L2 called "second hot".

It shouldn't matter which wire is black(L1) or red(L2). The color coding starts at the panel, not the pole top xfomer. You allegedly have a balanced system, where the currents through L1 and L2 are setup to be fairly close to identical so that the neutral current is close to zero. If you have a load imbalance due to too many breakers on one phase, you're doing it wrong. Put a clamp-on amps-guesser around the neutral wire and make sure the normal current is fairly low.

Narrow pulse width glitches will not show up on a voltmeter. Take a pulse generator and see how long it takes for your meter or DVM to respond. If your flicker is narrower than the meter response time, you wont see much voltage change. I suggest you use a step down xformer to about 12VAC and look at the glitches on the xformer secondary with an oscilloscope.

I dug ditches for an electrician in college. I have no idea what I'm doing.

Well, if you really want to find the culprit, and you think it may be in the house, just put a very big load on each circuit and listen for sparks. If there's a bad connection, it will soon either fuse to an open circuit permanently, produce visible arcs, or start a fire which burns the house down. Please have a fire hose and your insurance policy handy when trying this method. I've actually done this a few times and found bad connections by turning off the lights and looking for the sparks. Most were crappy push-in connections in light switches and receptacles. I think I also found a few loose screw terminals on other receptacles. However, during the inspection, I also found where the mice had chewed through the Romex, exposing bare wires. Fortunately, there was no connection and no fire.

Hmmm... have you considered an exorcist? Kinda reminds me of how a haunted house operates.

Lovely. If it was an intermittent breaker, all you've done is move the problem to another branch of the house. May I suggest using a brand new breaker instead?

Nope. It's time to replace the breaker. Your test does NOT prove that it's the power company. Their responsibility ends at the meter. Most likely, they'll suggest you call an electrician to deal with a problem on your side of the meter.

Think of it this way... if it was the power company, and one phase was intermittent on the pole, or there was an arcing insulator on the pole, then half your house would be flickering. It's not, which means that the problem is mostly likely after the breaker panel, probably on the circuit that you've identified.

Lovely 2.0. That just hides the problem.

If your 5v dip in voltage is correct, and your entire house is flickering (it's not but please double check), then it might be the results of hi-v arcing across the insulators. However, if only one breaker circuit is affected, it's some load connected to that breaker.

Since you posted this to a design group, instead of an electricians group, I suppose I could design something to help locate the arcing if it's in your house. Just take two identical isolation xformers and connect them to the two inputs of a dual trace storage oscilloscope. Plug the AC ends of the xformers into two widely separated wall jacks on the same breaker. When the flicker is captured on the screen, there will be a time difference between the two traces, which is equal to the difference in propagation time from whatever is arcing, and the two xformers. If you know approximately the wiring lengths involved, you can calculate the approximate location of the arcing. I've done stuff like this on telco lines, but haven't tried it on AC power. No warranty expressed or implied.

Good luck.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558
Reply to
Jeff Liebermann

(triplex).

There are companies that perform power quality and transient analysis, using various types of equipment.

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Some equipment:

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Something like the Fluke is about $3000, but here is a plug-in analyzer for $195:

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Since this is an electronics design newsgroup, I might suggest building such an analyzer as a project. It should not be too difficult to monitor the voltage on both legs with filtering to detect momentary fast transients as well as longer term droops or overvoltage conditions. You can also record the actual waveform by sampling at about 1200/sec, with a pre-trigger buffer, to see the waveform before, during, and after anomalies. These recordings can be time-stamped so you can determine when they occur, and synchronize the disturbance with other events, such as motor starting, loading, and stopping.

Your problem seems to be momentary drop-outs or overvoltage transients that could be caused by the transformer (pole pig) or any of the wiring from that point into the distribution (breaker) box. Then it is also possible that equipment connected to one line (L1 or L2) could be the culprit, but an extra load on one leg may cause its voltage to sag, while the voltage on the other line will rise, due to load imbalance and neutral current and associated voltage drop.

I have designed and sell equipment for monitoring current from 5 amps to

10,000 amps, and it can display, analyze, and store waveforms. I am replacing the older versions that use MSDOS and a parallel port, and I have a box with 20 or more working boards, which need just a 16VCT transformer and either a shunt to measure current, or 200k resistors to measure voltage using a precision differential amplifier. I could send one to you and you can download the software if you are interested. I have new boards that use the USB port and Windows software, but they are about $350.

See

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Good luck,

Paul

Reply to
P E Schoen

A bad neutral connection can cause this. If it opens completely, you will cause a lot of damage to appliances, and blow out a lot of light bulbs. I had to help a neighbor a few years ago when an electrician couldn't figure out what was wrong. There were five bad terminals in the Neutral, between the pole, and the last breaker box. Luckily, the wire had enough extra at each lug, to allow it to be cut off, and connected to a replacement lug. A pair of voltmeters, one across each side of the

240 volts to neutral will help you troubleshoot it.
Reply to
Michael A. Terrell

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