Blowing Light Bulbs- <>20 per Month (Why?)

GA

Yes, first understand the problem before taking shotgun approach to fix it.

It very well may be line spikes that you are getting, but until you prove what the problem is you might as well call a ghost hunting company.

My suspicion exactly - voltage spikes. I have had the same problem, but only with incandecsent bulbs. I used to be able to get what the called "rural" bulbs which are rated for higher voltages(up to 140 I believe), but since I no longer have any incandescents in use, I no longer have the problem.

As suggested elsewhere, monitoring the line for awhile would reveal if this is the problem.

Agreed, monitor the mains for:

voltage .... if it goes high at times (eq end of industry day when lots of machines get shut down at about the same time)

......resonances in the system caused perhaps by a particular load source combination could result in standing waves in the distribution system - you and some of your neighbours could be sitting at peaks.

...... A local (industrial) user may have a very poor power factor resulting in large line voltages.

..... something on your power distribution branch may be switching a high power device on and off, causing large voltage transients....

Your won't know until you measure and record the results of voltage, current, phase(power factor), line transients, etc

have a look at <https://en.wikipedia.org/wiki/Voltage_optimisation>

I agree and should not be advise to buy one. This goes like, ranging $4K for a decent unit-Fluke for example.

Probably, read and have a tech guy figure it out how to install one of this GDT's

For only about $3~4 each worth to save your spending from getting light busted.

Your appliances is equipped with this, that's why most are not affected yet. But later sometime it will soon to follow.

Call a professional to handle this.

PWSalck - yes, 120V (now corrected)
N. America

re: Neighbors - Yes! not a detail I should have left off.
One neighbor, nextdoor - downstream, SAME PROBLEM.
One neighbor, three houses upstream - uses a bulb or two per year!!!

Given that information, the chances of its being a loose or intermittent neutral link have risen, so contact the power company and have it rectified without delay; ask them to supply light bulbs for the house and the neighbouring properties in perpetuity if it is unable to fix the fault!

Good luck.

<unsubscribes>

PWSlack please see general thread at bottom. Thanks

Wow man. Thanks. I have some cards such as these.

I kind of hate cards but they work.

FP&L power company?

Very good post, except for:

You said:

Take good quality notes and be sure (without it being obvious) that they know you are taking detailed notes.

How is he going to make sure that they know he is taking notes without it being obvious?

you get a GA ( man I hate helping you) your answer is about identical to what I'd respond.

Well, you and the power company have checked the source, but what about the individual sockets and wiring in-between?

1. 10 year old house that you have had for 7 years, leaves 3 years for the previous owner to monkey about with the wiring.

2. You don't say whether theses lights are on a switch, or lamps plugged into the wall outlets. If wall outlets, check the wiring on the outlets - they will almost always wire from outlet to outlet using the 'stab' connectors (which suck). If there are any loose/bad connections that will cause an increase in resistance. Since W=E*I (power=voltage*current), if the voltage decreases, then the current must increase to supply the same power to the bulbs. If you are talking about fixed units on a wall switch, check for those same stab connections on the switch, as well as the crappy wire nuts used.

3. Usual disclaimer: Don't do any of this, hire an electrician if you don't know what you are doing. The life you save could be your own.

Kilowatt0 - switched lights.. not sure if lamps do the same. We don't have many.
To be clear - You're not suggesting that a bad nut or wiring or two would cause 10-15 different switched lights throughout the house to blow, right? (I actually don't know whether that's possible)

It isn't.

• If it is custom at the house to turn on installed fixed lighting before using plugged-in lighting, then by the time the plugged-in lighting is energised the fixed lighting will have presented an increased load to the supply, thereby reducing the voltage.

Sounds like PWSlack gave you a "Good Answer".

"To be clear - You're not suggesting that a bad nut or wiring or two would cause 10-15 different switched lights throughout the house to blow, right? (I actually don't know whether that's possible)".

I never said a bad wire or two would cause the problem. But if it is like most homes, the contractor used the cheapest fixtures (switches, outlets...) he could get. Plus semi-skilled to unskilled labor (overseen by someone qualified, but not paying attention). Therefore it could have been systemic.

He did.

I didn't mean to imply that you said that. I meant to clarify.

I agree that it could be systemic. The house next door has the same problem, however. That's a lot of bad work as opposed to a centralized issue which it seems the odds are greatly in favor of. There's not a light in this house that doesn't blow including those four large clear glass ones in the strips over the bathroom mirrors.

JRaef - Thanks.btw - 5 SECONDS. Not minutes :~(
ok, maybe 20 seconds <being generous

yes, typo (120V)

I didn't know that one!

Wow, experience really paid you well. I would put my GA on that.

What you mean is intermittent inductive loads, I should say.

Have you noticed any variation in brightness for the lamps?

Unredundant - I don't notice brightness issues except when a light blows, which is usually when I turn one on.
I used to notice a lot of 'browning'. Not so much anymore. But perhaps I overlook it.(?)

PWSlack and ALL

Thanks so much for the input.

It seems you're right, PWSlack. For lack of knowledge, all I have going for me is persistence. I can create tickets until their eyes bl33d and perhaps that's what will cut it. But believe me, the 'good ol' boy' who came out here to look at it just talked about the difficulties of these kinds of issues as if it were 1. insurmountable and 2. MY problem - complete with story, allegory and closure.

It does seem like the problem is coming from them. I can create tickets daily. Any further, specific recommendations to this end would be great. (oncor electric)

If all else fails, ring the Managing Director and put this individual under the attention of the best local consumer watchdog television programme available, then watch the problem get resolved in minutes.

Good luck.

<definitely unsubscribed now>

I had an issue with the phone company and their insistence that I get a new phone (one week wait time) with my account, when I argued that the one I was talking to them on was fine.

It came down to me explaining that I was on call for maintaining critical refrigeration equipment. This gave me a "special code" which meant a phone the next day.

Perhaps some "condition" such as security would help in your and your neighbors case?

cant let the ice cream melt!!

Oncor Electric... so you're in either Dallas/Ft. Worth, Waco, Tyler, or Midland/Odessa... if it's the latter, I'm very sorry.

Seriously though, if it is the latter and you are in Midland/Odessa - there was a HUGE construction boom there as a result of the previous spike in the Oil/Gas sector. I know because we contributed to the boom by building a new facility there on 35+ acres a couple years ago and had a hundred or so out-of-town contractors plugging up the hotels.

Bottom-line - if you're in that area Oncor was under significant stress to expand their infrastructure rapidly and likely why your response from them is what it is. There response to us for new construction (read new revenue) was even difficult and slow.

But, even more so why the problem is likely to be on their end.

Another option is to stop by your City Inspector's Office. As a final measure, if you go with Response #1 and rent a tester, you can scan/post the readings here for further validation that is/isn't likely an external issue.

You present these as a random failures. Are you sure or are the bulk of the failures to just a few lights? Are these lights the same types? Before doing any thing make sure the power is off. Unscrew the bulb and check the contact in the base of the socket. Some times get bent and do not make good contact. Home owner before you could have been screwing them in to tight and bent the contact.

Also other have discussed to high of voltage at times. Try a 130 volt light bulb in a few of the lamps. See how they last.

I have presented much more information than that. Your entire first paragraph is full of questions I have answered already.

130 volt bulbs I found in another thread as well and am considering. Thanks for that.

Though not a good selling point for an honest home-seller. Were that to be relevant.

There is something to consider that there exists some condition in the house that leads to poor contact at the lightbulb base, causing overheating....I would use some conductive grease, just a smear, on the contact points of the bulbs to eliminate or elucidate this issue....If this is the problem, it's a cheap easy fix.....

http://www.amazon.com/MG-Chemicals-Carbon-Conductive-Grease/dp/B005T8ROWA

and the house next door?

Hard to say without definitive numbers and firsthand inspection, just subjective opinion and hearsay.....but theoretically the same problem could exist....conductive grease is a quick easy fix for worn out light sockets and moist environments....

I would contact the local Authority Having Jurisdiction (the people that perform electrical inspections) where you live and report the issue. They will have to check out a reported safety issue and few things get a utility moving faster than having the local inspector involved.

I'm sure you are getting great advice here, but I have to ask whether you live close to an active airplane runway. When I lived near one of those runways, I was losing bulbs at about the same rate as you are.

...and what do you suppose is the connection between a nearby airport runway and light bulbs burning out?

Or did you just move away to "solve" the problem?

Sorry, I thought it was obvious. The connection was acoustic noise that caused vibrations in all filaments. I never was able to separate acoustic vibrations from earth transmitted vibrations, but I am reasonably confident that acoustic was the predominant source. Yes, I did move away to solve the problem. The new owners have had the same problem.

That had not occurred to me! How close was this home to the runway or takeoff/landing path?

I certainly can not say you were wrong, but I have some doubts. If you were right, then replacing the lamps with LED units should pretty much solve the problem.

Hi. We aren't too far from a private run, but most of the lights burn out when they're being turned on. Interesting story though!

If filaments are subjected to heavy vibrations during service, it weakens them, typically in a couple of spots. These become the very hot spots the next time the filament is energized (when there is a vary large surge in AC current while the filament goes from cold, low electrical impedance, to hot higher impedance). That is precisely when the weak spots (representing now a higher specific resistance than the rest of the filament) become very hot spots, and the tungsten melts during heat up, hence a blown filament.

If LED's are not subject to vibration induced failure, it is worth the money to replace using these, if they meet your lighting requirements, and if you want to save some on the electric bill. They are almost good enough, that if you use a lamp say for 8 hours a day with tungsten bulb, you could get away with leaving the LED on 24/7.

Thanks for that - but

Neighbor filled house with LEDs and stopped using them.

LEDs do not solve the problem.

If installing LEDs didn't solve the problem, then I think you have a pretty serious electrical problem!

If you are able to use a recording voltage meter of some kind, it will be important to know the characteristics of that device. If it is a slow-response device or measures RMS voltage, it may not "see" short-duration spikes.

which may lead to renting one...

Imagine me asking them for (and obtaining) a report and then getting them to tell me the qualities of the device.

I was told by yesterday's line guy that this would be a remote monitoring of voltage to my meter anyway - not a physical device (vs the "past")

I have very little knowledge of the capabilities of the "smart" kWh meters, assuming you have one. That is the only way I can think of at the moment that they could monitor remotely.

I just watched mine for a while. Its display cycles through current power usage (0.56 kW at the moment), Line-to-line voltage (244.xx V)(although it indicates 5 digits of data, I very seriously doubt if it is made to that precision), and total energy in kWh (a meaningless value for this discussion). It is conceivable that the device may monitor other values, and may be able to transmit those values to a remote recorder, but since its main purposes are for billing and for load sensing/controlling, I really doubt it.

Since it indicates line-to-line voltage, it presumably does not have any means to detect poor neutral grounding or imbalance between the two phases.

What you really need is a device that will record the voltage between the 120V line and neutral, or better, two such devices - one for each phase. One of the posts here said they could be purchased for under $100. If that is true, it would probably be a good investment for you. In fact, if such a device is available, I will go buy one, maybe two!

Happlebeack,

Call the Public Utilities Commission in your area. That will put a target on the utility's back to repair the problem. It definitely works in the New England area.

Your problem could be a bad neutral connection. Residential service is usually two phases and neutral, with the two phases 180 degrees apart, so you have 240 volts between phases and 120 volts from each phase to neutral. The neutral is connected to the center tap of the secondary winding of the step-down transformer on the pole.

Your 120 volt loads (lights, etc) are distributed between one phase and the other and 240 volt loads (dryers, ovens, AC, etc) between phases. If at some point there is a poor or broken neutral connection, the 120 volt loads on phase A would be in series with the 120 volt loads on phase B across the 240 phase-to-phase voltage. If these loads were not equal, one phase would have a higher voltage across it causing lamps on that phase to have a shorter lifetime.

Get a outlet tester at a hardware store and check all your outlets.

https://en.wikipedia.org/wiki/Receptacle_tester

the street he lives on has what I call "dirty power" the problem is more than his single home, its a utility issue

While I dread opening this can of worms yet once more... like an old spotted dog at a fire hall waiting for the fire bell to ring, I cannot resist the temptation.

You said...

Your problem could be a bad neutral connection. Residential service is usually two phases and neutral, with the two phases 180 degrees apart, so you have 240 volts between phases and 120 volts from each phase to neutral. The neutral is connected to the center tap of the secondary winding of the step-down transformer on the pole.

What you said echos the largest held misunderstanding concerning the nature of the split phase 120/240V consumer service used in North America.

There is not "two phases", there is only a single phase source. Do the math... two sources 180 degrees out of phase to each other sum to 0 volts when connected in series and not to 240 volts.

What the 120/240V consumer service is in use in NA is two 120 volt in phase sources connected in series. The only way that two 120V AC sources sources sum to 240 volts is if they are in phase with each other.

Forget for a moment that the voltage level change based on the frequency of the sources and equate this to batteries. To get 24V from two 12V batteries you must connectc them like... (+,-) + (+,-) and not (+,-) + (-,+), which would give you 0 volts. This is the exact same issue as if the sources were 180 degrees out of phase.

It only "appears" that the two sources are 180 degrees out of phase relative to each other when we use the "neutral" as a permanent reference point.

The concepts of "buck" and "boost" in transformer theory explain this quite well. Transfromer cores and windings have "polarity" marks on them for this very reason.

Yes, this can be a can of worms!

Whether the 2 sides are in or out of phase depends on where you place zero. Since the neutral is connected to ground in standard USA homes, that's where I place zero. if you take a dual trace 'scope with ground at the neutral, and connect one channel to one of the two phases, and the other channel to the other phase, one channel is exactly the inverse of the other; when one goes up, the other goes down. That's what I call 180° out of phase.

Mathematically, since the voltages have opposite polarities, you must subtract the negative from the positive to obtain the end-to-end voltage.

I like my fried worms with ketchup, you? LOL...

IMHO... they are not opposite polarity to each other. They only appear to be opposite polarity when, again, they are referenced from the neutral.

Why would you use any other reference when dealing with 120V devices?

I once taught in a classroom with a quad outlet. I plugged a computer into one outlet and its monitor into the other outlet of one pair, and it worked fine. I then plugged a printer into one outlet of the other pair. The instant I plugged the printer data cable into the computer, both the printer and the logic board of the computer were instantly fried! It turned out that one outlet pair had been wired on one phase, and the other outlet pair was wired on the other phase. If those two 120V wires had been in phase, there would not have been a problem.

Those were definitely opposite phases!

The power supplies in those devices should have made the AC source meaningless in how they worked together. I would imagine there was a serious fault in one of them that only became evident when connected to the quad receptacle you mentioned.

I would not use any other reference than the neutral. Using the middle point of the pair of 120V sources as the reference gives us all sorts of advantages. IE... the voltage between the middle to either end is 120V.

We could just as easily have decided to ground the far end of one of the sources. The problem here is the middle of the two sources would be at 120V to the reference while the far end of the series pair would be at 240V to the reference. Which, doing so, makes no sense.

Without a doubt... by fixing the middle point as the reference... we introduce a mirror effect that makes it look like the two sources are reverse polarity and 180 degrees out of phase to each other.

But... they are not.

Why oh why did I touch that can opener. LOL...

That would make the readings redundant ....again..... sort of?

I do not understand your comment.

"by fixing the middle point as the reference... we introduce a mirror effect that makes it look like the two sources are reverse polarity and 180 degrees out of phase to each other"

Thus making the voltage graph appear redundant.

Yep! I suspect it was capacitors rated at less than 350V, which would be absolute minimum for two devices plugged in to opposite phases.

"I would not use any other reference than the neutral." When you use that reference point, one phase goes positive when the other phase goes negative. That's opposite phases. I have very high confidence in what I see on the 'scope!

I guess we have to agree to disagree...

The power feeding a dwelling is derived from a transformer with a center tap.

Across the full output,you will measure 240 volts.

From the center to either side,you will measure 120 volts.

The center tap is connected to the neutral conductor.

These 3 conductors are fed to the house meter and main breaker panel.

If the neutral is missing,or broken,the 120 volt circuits,which were in parallel with each other across 120 volts,now become in series with 240 volts instead of 120volts.

Since current is constant in a series circuit,the voltage will vary according to the individual resistance of each item connected.

Some items may have very low voltages,and some may be very high,all at the same time.

Every time you add or subtract a load, the voltage will change.

If the neutral is intermittent,this can show up as spikes or sags on individual items in the house.

That is as simple as I can make it.

What is your point?

I am simply agreeing with you,that the voltages are not out of phase,simply different amplitudes of the same phase.

It is really a split-phase system,but is seldom referred to as that in common usage,and most people refer to it as 2 phase.

I hoped by further explaining where the lower voltage originates,that it would become clearer to others.

It is obvious that you know,and this should have been posted to the forum thread,instead of to you,but careless fingers and bad eyes come with age.

('Specially dem dang bi-focals!)

Thanks for the explanation...

"...that the voltages are not out of phase,simply different amplitudes of the same phase"

I have to disagree! If they are different amplitudes of the same phase, then one must be 120V and the other must be 240V. This is exactly what you would get if you ground one end of the transformer, rather than the center tap.

But we don't ground one end; we ground the center tap, thereby calling that point zero volts.

Here is a standard transformer full-wave power supply circuit:

Would you say the currents through D1 and D2 have the same phase? Of course not! I'm sure you know that each diode supplies current half the time, when its respective supply line is in the positive half of its cycle, and because of the 180° phase shift between the two supply lines, each diode can conduct when the other is not conducting.

Remove the diodes and everything else to the right, replace the 120 VAC with 12kVAC and you have exactly the circuit of what is mounted on the pole outside my house.

When you say the two "hot" wires of a split phase circuit have the same phase, you are (perhaps unconsciously) placing your reference point at one end of the transformer, NOT at the center tap.

Perhaps it is nothing but semantics, but I insist that as soon as you call the center tap zero, you have 2-120V sources 180° out of phase.

If you place zero at either end, THEN you have a 120V and a 240V source of a single phase.

Yes... it is "semantics". Adding a neutral center tap to a 240 volt winding (or two 120V windings in series) cannot and does not create a phase shift. This is impossible.

When we refer to the neutral pouint as 0, to keep the polarity reference in such a way that it is generally understood, we introduce the appearence of the phase shift.

I agree that alot of people consider the phase shift to be present. The laws of physics clearly cannot be ignored and mathematically it is impossible for two equal potential sources that are 180 degrees shifted to each other to sum to anything other than 0 when connected together in series, whether we chose to consider the central tap as being 0 volts or not.

Take a look at a 208Y/120V 3 phase system. Across two phases we see 208V and not 240V, why, beacause of the 120 degree phase shit between the sources.

Perhaps we should consider this discussion closed as there is no way that I think we will come to agreement.

closed!

Probably not. If they were out of phase as you contend then the "frying" would have taken place when you plugged in the power cables, not the data cable. The fact that you smoked everything when the data cable was connected indicated that there was an isolation/neutral/grounding problem.

It was very common in the early days of computing where some internal power supplies were grounded and others had floating grounds; the innocent looking data cable had internal signal grounds and a sheath attached to the metal plug cover which provided a handy path for large ground currents to flow between units, especially if they were connected to outlets fed from different breakers, which was often the case when two outlets were in the quad configuration. Any difference in run length, loading, poor connections, etc. lead to a possible voltage difference across neutral/grounding wires, which released the magic smoke in the very sensitive electronics of the day.

That's what lead to the development of isolated neutral (orange outlets) in the US. Over time the electronics guys got more savvy and started isolating their power supplies from the AC line to alleviate the sneak paths through their equipment. Now the orange outlet serves to provide a "clean" signal ground and the power supplies are double insulated to prevent any stray paths for voltage/current from appearing at the signal pins/grounding pins.

"If they were out of phase as you contend then the "frying" would have taken place when you plugged in the power cables..."

NO! Each outlet had the correct 120 VAC between its respective "hot" and neutral, so any single 120 VAC device would work normally in any one of the four outlets, and any two 120 VAC devices would work normally, and could be connected together without incident, as long as they were plugged in to a vertical pair of outlets.

As soon as one item is plugged in to the left outlet pair and another item is connected to the right outlet pair, now there is 240 VAC (≈320 V peak) between the 'hot" lines of the two items. Both the computer and the printer had switching type power supplies, so theoretically the low voltage systems should have been isolated, but the grounding capacitors were designed for 120 V operation, so probably were rated around 200V. The 360Vpeak was way to much for them to handle, so it released the magic smoke!

This occurred over 30 years ago, to the school's only Mac (I believe it was a Mac 512k). Fortunately, I was then working part-time as a Mac service technician, and was able to find a logic board that had a bad solder joint. I repaired the bad joint and installed that logic board in the school's Mac, and sent the fried board back to Apple.

The instant I plugged the printer data cable into the computer, both the printer and the logic board of the computer were instantly fried!

I am thinking that what happened was:

(1) neutral was connected to ground in the devices and

(2) someone had miss-wired the plug or socket so that hot and neutral were switched in one of the devices.

This would result in the ground (shield) being "hot" on that device. The device would still operate until the two grounds were connected and the fireworks started.

Sorry, but NO!

As soon as the failure occurred, I turned the breakers off, and took off the cover plate. A single 4-wire cable fed the box. The green wire of course was connected to the ground terminal of both outlet pairs, and the white was connected to the neutral of both outlet pairs. The black was connected to the hot side of one outlet pair, and the red was connected to the hot side of the other outlet pair. Since there was no sign of any damage to anything in the box, I turned the breakers back on. I then measured the voltage between the two hot terminals, and indeed it was 240 Volts.

There were quad outlets all around the room. As soon as the problem occurred, I checked all the other outlets; all the rest were wired alternating between red for all four outlets in a box, and black for all four outlets in a box. This single outlet was in a separate location, where it didn't conveniently pair with any other nearby outlets.

This was a relatively new portable classroom; I had been teaching (to answer HiTechRedNeck as well) physics, electronics, and computer science in this classroom for five or six years, and in other classrooms for a total of 22 years before the incident. I continued teaching the same subjects for another 10 years before retiring from teaching and starting my engineering career.

This summer marks 20 years since I retired from teaching.

Sorry, but NO!

I see you've checked out the power supply. I am at a loss to explain what you describe other than a fault inside one of the devices or their power cords. Even powered from separate phases, there should be no difference in the potential on the grounds (or neutral for that matter).

See my post #99.

There are very commonly capacitors between various lines and ground, to suppress transients. Since these devices were designed for 120VAC operation, those capacitors probably had a voltage rating of 200-250 VAC. Somehow, one or more of these capacitors apparently saw the full 340VP-P, and couldn't handle it. Upon disassembling the devices, which I did, it was very obvious to see the blown capacitors, but after 30 years, I don't remember any more details.

What subject did you teach?

I hope it was not electrical in nature.

What you had was a difference in potential, probably caused by conflicting grounds/hots,which does not necessarily require a difference in phases.

Some older o'scopes required an isolation transformer to prevent shorting to a grounded chassis.

See my reply (post#94) to Rixter.

"I hope it was not electrical in nature." It definitely was electrical in nature. I'm very disturbed to hear your low confidence in my knowledge of things electrical. I have indeed been learning about electricity for just over 70 years, and continue to learn more... I assume you have read more than a few of my posts, since we both Joined CR4 in 2006.

Yes, my personal 'scope (a Tektronix 2236) has the ground side of the probes connected to chassis ground, which of course is also power ground. I do have, and use when appropriate, a 120V isolation transformer.

Since you have explained your qualifications, please help me understand the difference between "difference in potential" and difference in phase.

They can give the same apparent results,but have entirely different sources.

Consider a potentiometer:

If you have,say,12 volts DC across the pot,as the wiper moves from one end to the

other,there is a varying change in the potential(Voltage) on the wiper referenced from

either end,from one point of reference increasing,from the other, decreasing.

There is no phase difference,simply a difference in potential.

Now consider a single phase center tapped transformer:

If you had a wiper referenced to one end of the secondary,as you moved the wiper

across the secondary coils,one turn at the time,you would get a varying difference in

potential.

Depending on which end you used as a reference,it would be increasing or decreasing.

When the wiper reached the center of the winding,the secondary voltage would be equally divided,or split.

This is a difference in potential, not a phase shift.(IMHO)

You are simply measuring a portion of the magnetic flux in the secondary.

Where is the error in my logic here?

Just like Northof60 seems to do unconsciously, you are using one end of the transformer windings as your reference point. In the split phase system used in virtually all homes in the USA, the center tap of the transformer is grounded, so the center tap must be the reference point. All home voltages are measured using that as the reference zero point.

Here is the situation:

(HV waveform NOT to vertical scale) Using the center tap as zero, at the instant the upper half of the transformer winding is producing its peak voltage of ≈+170V, the lower half of the transformer winding is producing its peak voltage of ≈-170V. That's a potential difference of ≈340 Volts, due to the 180° phase difference between the two outputs.

I understand your position and your reasoning. There is nothing unconscious about my position on this issue. What you describe and how you understand the nature of the system is against the laws of physics.

Before this devolves in to a real argument that ruins relations here... this was the last I am going to say on the subject.

Let's put a lid on this can of worms. Instead of looking at the secondary, let's look at the primary side. How many primary phases are there? One.

If there were three secondary windings on the same leg of the core as the primary, would there be a way to get three distinct phases out of it? No.

All you will have are three single phase windings whose output voltages are in phase with each other (assuming the polarity marks are aligned correctly), you cannot possibly interconnect them to create a balanced three phase system.

If there's only one primary winding and two secondary windings on the same leg, it's called a Split Phase System. If there's a 90º phase angle difference it's called a Two-Phase System, and that requires a two phase generator or a special three phase transformer with a center tapped primary (not secondary) known as a Scott-T transformer.

I don't see how your post puts a lid on anything!

"If there were three secondary windings on the same leg of the core as the primary, would there be a way to get three distinct phases out of it? No."

That is correct. Indeed you can't get three, but you can get two, each 180° of phase with the other. The third winding would be superfluous, or could be used to provide additional current if correctly connected in parallel with one of the other windings, or additional potential if correctly connected in series with one of the other windings:

Here are your three windings, all wound in the same direction with start at the bottom. Notice I've added arrows indicating the direction of positive current flow.

The third winding is irrelevant. The important point is that positive current flows away from the reference point to the load in the bottom winding, while positive current flows towards the reference point from the load in the other windings. It is this opposition of current flow directions that makes the upper two windings 180° out of phase with the lower winding.

What we have here is a failure to communicate/understand/acknowledge the difference between a split-phase system and a multi-phase system. Unfortunately personal opinions supported by self-generated graphics cannot trump basic engineering science.

To simplify matters we will use a one-to-one ratio transformer with two coils wound in the same direction on a single core, each with 240 turns plus a tap at turn 120 of the winding. If we put 240 Volts on one winding the other winding will measure (at no load for the purists out there) 240 Volts, we also hardwire Voltmeters across the endpoints of each coil, and we never remove them. Forgetting about the center tap for a moment, can we agree that this is a single phase transformer? After all 240V in equals 240V out.

We now take another pair of Voltmeters and attach them between the endpoints of the primary winding and its center tap, each will read 120V, while the original Voltmeter still reads 240, as does the secondary Voltmeter, because we haven't changed a thing, it's still a single phase transformer fed by a single phase source.

We now take yet another pair of Voltmeters and do the same thing on the secondary side without disturbing any of our previous connections. Of course these Voltmeters also read 120V each, and because we have not changed anything about the original configuration, we still have a single phase transformer fed by a single phase source. No magic, no phase shift, no ground, no neutral, just the same old original single phase system that we started with.

It's a naming convention, nothing else.

"What we have here is a failure to communicate/understand/acknowledge..."Correct so far.

"...the difference between a split-phase system and a multi-phase system." In this thread, I have never discussed anything other than a split-phase system, because that is what is used in virtually all homes in the USA and that is the kind of system that provided the electrical energy to the classroom where the problem occurred.

"Unfortunately personal opinions..." I am not discussing an opinion! I am discussing facts observable and repeatable by any experimenter with appropriate equipment anywhere in or out of the world!

" supported by self-generated graphics cannot trump basic engineering science." I'm sorry, but I have a very graphics-oriented mind. I generally don't think in words; I think in illustrations. You degrade my illustration(s), implying that it(they) is(are) in error. If there is/are errors in my drawing(s), please point out the error(s) and I will gladly correct them.

The three following paragraphs of your post are absolutely correct, but ordinary AC voltmeters do not indicate phase/polarity/current direction.

This is simple arithmetic!. If you consider one end of the secondary to be zero volts, then the three terminals have 0, +120, and +240V respectively. If you now redefine the centertap to be zero volts, you have subtracted 120V from that terminal, and must subtract 120V from all the others, so the voltages are then -120, 0, and +120V. That negative sign is NOT trivial; it indicates direction of current flow.

In my latest drawing I provided arrows indicating the direction of positive current flow. All those current flow arrows indicate a clockwise flow through the coils/windings of the transformer. YES, it IS a single phase transformer.

BUT, when you have zero at the bottom end of the transformer, the positive currents of both windings circulate from right to left through the zero point, and thus are in phase with each other.

When you move the zero point to the center tap, positive current from the lower winding flows from left to right through the zero point, while positive current from the upper winding flows from right to left. When the sine wave crosses zero, both (instantaneous) voltages swap polarities, and both currents swap directions. With respect to center tap zero, the two voltages always have opposite polarities and the two currents always flow in opposite directions. THAT is a 180° phase difference.

PLEASE, anyone, point out and tell me how to correct any and all errors in this post and/or my drawings!

Since we both agree that this is a single phase transformer, and not a two phase system, then the lid is on the can. btw, I like your graphics, sorry if you felt that I was attacking them per se.

Follow the neutral from the secondary of the pole transformer,and you will see that it is actually connected to the common ground of the power system,same as the primary.

It also connects to the MGN that runs down the side of the pole to a coil of wire on the bottom of the pole.

It also goes inside the main panel in the house.

This is connected to an external ground rod driven below the meter.

Any copper plumbing is also connected to the same ground rod,and if this is the main panel,and not a subfed panel,the green chassis ground is also bonded to the neutral bus inside of the panel.

If it is a subfed panel, the bonding strap is not used.

In effect, one end of the secondary is already grounded.

I marked your post off-topic because it is and because it is wrong. The center tap of the secondary is grounded, not one end. Post 88 made it very clear. You have broken redneck rule #52 (me too?). So the primary is 1 phase and the secondary has 2 phases when referenced to the center tap (which is the only sensible place for the reference), but it is called 1 phase probably because that is what the power company delivered to the pole). That doesn't explain the computer and the printer frying. All outlets should have had the ground to the same place, and all should have had the hot isolated from their chassis. There was probably an equipment malfunction, and DK made the wrong assumption.

You are right..my mistake I meant to say that one end of the primary is grounded,and the Neutral(aka Center tap) is grounded to the same point.

I need to proof read a little better,I guess.

New Rednek Rule:52A

Paragraph A:Error Prevention:

Part 1: Proof read for content forward twice, proof read for spelling errors backward twice,post once.

A mis wired power cord(hot and neutral reversed) on the printer could have been the culprit,especially if the ground prong was broken off or if it was a 2 wire cord.

This could send 120 volts through the signal cable to the ground on the other equipment.

Sorry but you are confusing "Split Phase" with "Split Winding" and "Center-Tapped" or "Multi-Tap Winding" terminology which is feeding this circle of confusion.

The example you have shown is that of a small 110/120V to 24V appliance control power transformer which utilizes "Center-Tapped" methodology. The tap is placed at the mid point of the secondary winding to allow half the voltage available in reference to the neutral to be used.

This is in no way indicative of a computer power supply other than that the computer power supply transformer has multiple voltage taps.

Residential, commercial, and industrial single phase 240/120 transformers normally use two separate phases/windings or two separate transformers on the primary side to provide two separate phases/windings on the secondary side of the transformer for 240V and with the neutral connected to the center connection of both secondary windings to provide 120V-to-Neutral.

These transformer windings can be connected in different configurations to meet the service voltage requirements of the application.

In your case you were working with a "Split" outlet circuit with a "shared" neutral.

This is very common in applications such as laboratories, commercial works shops & equipment rooms, as well as in classrooms and IT service applications.

"Splitting" the outlet allows individual circuit breakers to feed each individual receptacle and therefore permits dedication of that outlet for use to one machine/computer/light.

In residential applications this method is often used in bedrooms and living rooms to allow individual control of lights/lamps while still keeping the power outlets adjacent to the bed(s) or desk or other furniture energized at all times.

Unless there was a wiring error in one or both of the equipment plugs or a wiring error in one or both machines there is no way 240V could be impressed in either machine by them sharing a neutral.

All neutrals are connected together on the neutral bus at the distribution panel for all circuits feeding out of that respective panel.

Splitting an outlet with an individual circuit breaker feeding each outlet receptacle then plugging two separate individual pieces of equipment into the receptacles is no different than plugging the same two pieces of equipment into two separate fed 2-gang receptacles that are ten feet apart in the same or different rooms which are fed by separate breakers.

It is possible especially with the earlier computers that interconnection of two machines fed from different power sources when connected together via the communications ports could have dire results.

The early machines often suffered poor quality power supply issues as well as incorrectly configured communications ports and channels.

In some cases the PS was inadvertently capacitive coupled (connected) on the secondary low voltage side back through the case ground which caused severe high voltage issues in the motherboard and auxiliary devices.

The changes you made simply moved both machines to the same circuit breaker which removed the difference in potential between the machines caused by incorrect or faulty wiring.

"The example you have shown is that of a small 110/120V to 24V appliance control power transformer which utilizes "Center-Tapped" methodology."

Although this post indicates that it is a reply to my #99 (distribution transformer to 120/240 service), I presume this sentence refers to #80 (Full-wave Low Voltage power supply). Before the introduction of switching mode power supplies, this was the standard circuit for powering virtually all DC devices from an AC source.

"The tap is placed at the mid point of the secondary winding to allow half the voltage available in reference to the neutral to be used." No! The tap is placed at midpoint to enable full-wave rectification through a pair of diodes. If multiple voltages were required at significant currents, a separate center tapped winding was commonly provided, with its own diodes and capacitors, etc. Obviously, there are lots of other possibilities, including diode bridges, voltage dividers, and voltage regulators...

My point in showing the drawing was to illustrate a well-known circuit, where it should be obvious to everyone educated in electronics/electricity, that current alternately flows through the upper and lower diodes on opposite halves of the power line cycle, due to the 180° phase difference between the currents flowing through the upper and lower halves of the transformer, due to using the center tap as the return point for both transformer windings, and thus defining the center tap as zero voltage.

If one understands that circuit, then it should also be obvious that the currents from the two halves of a center-tapped distribution transformer also differ by 180°, again based on using the center tap as the zero reference point.

Correct, and GA! I should have included the waveshapes on my full-wave rectifier illustration. The one thing I would have done differently (on your drawing) would have been to show the output waveshapes with zero at midlevel, since both outputs go positive and negative at opposite times:

Obviously, the turns ratio will be different for different HV supplies. I'm under the impression that mine is 12kV...

Pretty neat.GA

You have an actual 12V system from your provider??? Did you mean to say 120 VAC?

Unusual line voltage changes are not particularly predictable or detectable in any five minute window. Listen to SE (Solar Eagle) and follow all his provided links, he knows what he is talking about, and is leading you to good water. It is up to you to drink it.

Data loggers can be had for less than $100, that could in fact tell you all you need to know.

The only other suggestion would be to install a large isolation transformer between you and provider, and put a large UPS behind that to help maintain any sagging potential (that would normally just ruin appliances, not light bulbs), but also tend to level off potential upswings (I think), and eliminate spikiness.

Hope that helps. We too burn out light bulbs more than I would like to admit. Usually in the garage where my wife leaves a light on for cats that can see in the dark. Or the front porch light, where she complains that the LED bulb I installed throws light up, but not out and downward from the ornamental antique appearing fixture.

Yes, in-fact - I have managed to get 9v from them as well to run my old walkman and next month they're sending me two lines straight from the pole each with AA voltage for my 1970's vintage electrical table style lighter and electric toothbrush.

They refuse to provide power for my hearing aides however. I try to argue that I really need them, since with all of the burning bulbs, I can't see for $%@^.

:~)

Another "bad neutral" story:

A few years ago, I was noticing that lights would vary when the microwave oven started and stopped. I "plugged in" a voltmeter -- jammed the leads into a receptacle, asked someone to heat up some water, and read the voltage change. (I don't remember how much variation there was.)

I called the local utility, and they sent someone out. The service person found that squirrels had chewed the crimped lead connector on the neutral cable at the pole. They said the squirrels chew those things all the time.

A loose connection up on the pole could certainly affect more than one house.

That is why my dogs bark at all squirrels in transit on the power lines.

Smart dogs!! :~)

I have one unusual squirrel that has bugged-out eyes, and a tail that looks like a bottle brush. I think it may have gotten in-between the chewed crimp connector and the conductors. I call him "Series".

Rough service light bulbs will help if it is vibration related. Good ones will allow you to drop a lit drop-light without it breaking.

Higher voltage bulbs will help if over-voltage is the issue.

Traffic light bulbs are available that will take a beating, and still continue to work. They are available in 120 as well as 130 volt versions. The problem is that you pay for that quality. They are more expensive from Grainger, than the LED bulbs are from Ikea.

So many great comments!!

I had the local provider out again yesterday. This guy was more helpful, ran a load test, showed me that it does run a little high - but not to that 5% mark. Stating that I may be close to a substation, he made the suggestions for the 130W bulbs and getting a voltage recorder put on the meter. I initiated the process for a recorder but it's going to be performed by the local provider themselves. Being in TX, I am removed from the local provider and since the 'service provider' doesn't have technical personnel, I am talking to someone who's talking to someone who'll be talking to someone about getting this done. We'll see how that goes! I'm working on getting a copy of that report for myself.