It's a gusty day. I was in a house across the street when a light
flickered for two seconds. Digital equipment in three rooms had to be
reset: microwave, answering machine, computer, and television.
I've always assumed such flickering comes from arcing in a transmission
line, but digital clocks in two other rooms were not affected. The same
transformer supplies my house, and none of my digital equipment was affected.
What could cause power fluctuations that would affect household
electronics on some circuits but not others?
The clocks probably have battery back-up so that the alarm will not be reset
if the outage comes when you are sleeping.
Some other equipment had large enough storage capacity for the power supply
so that it will survive a brief outage without resetting.
I suggest that you may want to invest into some whole house surge
protectors in addition to any point source protection you now have or may
add. That kind of problem can be an indication of possible surge problems.
Most newer equipment is less sensitive to surge issues and they also are
better able to maintain a few seconds of outage and still maintain their
internal memory. I suspect what you found was that some of your equipment
is older or of low quality than those that maintained their time.
The flickering of the ceiling light lasted long enough for the lady of
the house to ask, "What's that?" and me to turn around and see it.
After finding four electronic devices scrambled in three rooms, she
checked the bedroom clocks, saying they always go out if the power
flickers. They were fine. It makes sense that the breakers for the
side of the house with the problems would be on the same side of the
The same transformer supplies my house. I have computerized stuff
plugged into both sides of the line, and none was affected. However,
the line that supplies my neighbors supplies another neighbor, who says
she had to reset her electronics after her lights flickered at the same
I guess it's a splice up above. I see a couple of popped splice covers
up there; maybe they overheated sometime due to resistance in the
connection. Could a bad splice have welded itself during the
flickering? As it didn't affect my service I suppose I shouldn't be the
one to report it. What would my neighbors risk by not reporting it?
You are making assumptions rather than first providing
facts. For example, how do you know breakers on one side of
the breaker box would be on same phase? When a 240 volt
breaker is installed, it provides both phases from same side
of that box. Why does this make sense:
That is only speculation. It is responsible to ask why this
strange failure occurred. But it leads to nothing useful when
What could have caused the problem? Let's see. I only
have one idea. Therefore that *IS MOST LIKELY* the reason for
your problem. Some others posted using this logic.
You have provided woefully insufficient information for
anyone to post a probably reason. But even worse, your own
posts are based in speculation. No wonder others posted using
only speculation as a probable reason.
Every electronic appliance has a unique cutoff voltage.
These are numbers so necessary to appreciate what happened.
Intel even states how low voltage can go and computer still
works just fine. Voltage so low that incandescent bulbs are
at less than 40% intensity. Other appliances may cut out at
higher voltages. Again, without that number or knowing which
phase each connected to, then no useful facts are available.
Tom MacIntyre once identified a 120 VAC TV that worked until
voltage dropped below 37 volts. All other electronics could
shutdown while the TV worked? What does that tell us about
household wiring? Nothing.
Every appliance must also work so many seconds after power is
lost - as both Mark and PrecisionMachinisT noted. Another
number that varies depending on that appliance's internal
design - and that was not provided. Just more reasons why
what did and did not work provides nothing useful.
You don't have numbers. Your facts are mostly speculation.
Don't speculate as other posters have done. To learn, at
minimum, you must measure voltages between wall receptacles
that did and did not lose voltage. If for no other reason to
learn which phase each receptacle is connected to - without
That'a true. My neighbors don't have an instrument recording the
voltage at each outlet.
Do you mean visible light or total radiation? Why not say what voltage
Here are facts. An interruption too brief to see even at night will
knock out my phone clock, microwave clock, and computer. The problem at
my neighbors' was conspicuous in daylight as the lights went on and off
for several seconds. My house was fine. I'd say the problem did not
affect the transformer output terminals.
Here's another fact. The reason my neighbor checked the bedrooms was
that in her experience, any time she had to reset the stuff on one side
she would also have to reset the bedroom clocks. She was amazed to find
My TV seems more sensitive when it's off. An interruption too brief to
stop my microwave clock will keep my TV from turning on later. I did
not have to reset it yesterday.
Those appliances that work so many seconds without power could be
useful. How many seconds must they work? Are they expensive?
As a matter of fact, I was about to go over there with a DMM and an
extension cord this afternoon to check phases. Instead, I called a
neighbor who lives on the other side of them. She told me that when my
neighbors' lights flickered, so did hers. She had to restart her
computer and reset digital clocks.
By the process of elimination, I think that in the 50-mph gusts that had
been occuring that day, one of the splices feeding their houses got
worked into a high-resistance condition for a few seconds. Have you a
better explanation for the facts?
Rightly proper to look into this anomaly before it becomes
serious. If nothing else, fixing a problem before it happens
can only be a good thing. Using that extension cord and meter
does do one thing important. For example, proving all
interrupted devices were on one phase, then empowers a utility
crew to repeatedly check only one spot until they find
something. If ailed devices are on both phases, then the
utility crew is encouraged to on a neutral wire problem - a
failure that may eventually get destructive if not found.
IOW by obtaining that one little additional fact, then a
utility crew has better reason to play more aggressively
(concentrate their attention) only on those live wires that
can explain your 'unique' symptoms.
In specs for computers (for example), a 100% loaded computer
must keep working when power is lost for 16 msec. All will
typically keep working even longer. If voltage drops so low
that incandescent lumens are less than 40%, then a computer
must still work just fine. These are characteristics defined
by specs for computers. Other devices such as digital clocks
may not be so resilient. I said seconds. Not full seconds.
Milliseconds. Every device will keep working a fixed period
after power is completely lost. Some just work longer.
Computers tend to be some of the more resilient to dropouts.
Some clocks tend to withstand dropouts longer. Some clocks
may have a battery or internal capacitor so that short
interruptions don't bother them.
But again, determine if all 'interrupted' appliances are
only on one phase or both. A utility crew would be more
likely to aggressively shake the suspect live wire rather than
uselessly checking all. That information also tends to make
them more believe you do have an intermittent problem.
Oh no, 240! The affected outlets represent both sides of the
transformer! There goes my speculation of a loose splice on a secondary
line. I don't know why so much in two houses had to be reset but
everything at my house was fine.
(It's been years since I looked inside a breaker box. That's why at
first it seemed natural to me that all the switches on one side would
come from the same side of the 240-V supply.)
Maybe loose splice on neutral wire? But this would also
cause some lamps to sometimes glow brighter and some
incandescent bulbs to fail faster. Defective neutral is also
just another human safety reason why the earthing ground rod
is important attached to breaker box.
Symptoms are getting squishy. Once it appears contained, it
squeezes out somewhere else.
I can ask if they've noticed bulb problems. I've been over there many
times in the evening and the lighting was steady.
I know a retired lineman who runs marathons. Today at the track I
managed to keep up with him long enough to inquire. He said,
"Whole-house surge protector."
He's right in that I have one and they don't. What I observed was rapid
dimming of bulbs in a fixture as if it were repeatedly being switched
off. I suppose spikes could have scrambled the TV, answering machine,
and microwave, but the computer was plugged into a brand-name surge
protector. Does his guess sound good?
I don't understand the benefits and limitations of the surge protector
in my breaker box. It's a semiconductor clamping device that I
installed about 1985. At New Years of 1999, ice brought down
high-voltage lines a few miles away. In spite of my surge protector, my
TV and stereo were damaged so badly that they weren't worth fixing. (A
plug-in protector prevented damage to my computer, which was on.)
Brand name plug-in protector are promoted like Listerene and
Geritol. There is no such thing as a quality plug-in
protector. Take a $3 retail power strip. Add some $0.10
components. Sell it for $15 or $50 because myth brokers now
call is 'quality'. Worse still, the adjacent protector can
even complete a surge destructive path through the appliance.
Just another little fact they forget to mention.
A 'whole house' protector connected 'less than 10 feet' to a
single point ground is essential for every home. Every phrase
in that sentence has critical importance. 'Whole house'
protector is not required for human safety. Therefore no
building code requires this effective protector. (Remember,
the protector is not protection. Earth ground is the
protection. But that discussion is irrelevant here).
Although a 'whole house' protector should be priority for
every homeowner (especially with summer T-storm season
approaching), still, that protector is not a solution to your
flickering problem. You (and neighbor) suffered a voltage
drop - a brownout or sag - so low that even electronic
appliances were affected. Many different electric problems
exist. A transient is a high voltage. A brownout is low
voltage. A surge protector is only for high voltage
transients that occur typically once every eight years.
Protector would do nothing - completely ignore - a brownout or
Yes, the linemen properly informed you of something
essential for every transistorized building. Absolutely
essential. Something missing on most all buildings.
Something so important to transistor safety that every lurker
should be now planning trips to responsible stores such as
Home Depot and Lowes. But surge protectors - the effective
'whole house' type or the scam plug-in type - will provide
nothing for this brownout or blackout problem.
Among suspects should be inspection of the circuit box. For
example, some Federal Pacific breaker boxes have been known to
burn down the building. Flickering would be a symptom of
future serious failure. The flickering may be nothing. Or it
may be symptoms of a future and major problem. In previous
posts I mentioned, in passing, the inspection of many things
such as the earthing rod. Inspection of that circuit box
(including feeling for heat on non-conductive surfaces) is
another. Immediately cannot say if those inspections would or
would not explain the strange flicker. But then even the
military demands such inspections every five years or less.
Yes, even an intermittent neutral wire does not explain your
symptoms. However this assumes just one problem. It might be
a combination of intermittents that conspired to cause that
flicker. Best we can do is inspect the usual suspects, and
'keep your ears on' for future symptoms. That strange flicker
would bother me to no end - just like the near disaster of a
Space Shuttle one full year before Challenger exploded for the
same reason. The engineers never stopped asking why and
therefore could have saved Challenger; if their management had
minds of innovators instead of bean counter mentalities.
Best to do as you are doing and to inspect those various
suspects previously recommended for inspection. Sorry I
cannot offer up a likely suspect. Best I can do is add to the
list of suspects and encourage you to keep being suspicious.
Outlet strips won't do much and are sometimes called surge protectors.
With a surge protector, I guess you got MOVs or something else to dump
surges, inductors to show high impedence to transients, and something to
blow quickly if an MOV can't handle a surge.
With a whole-house protector, all you get is something to dump surges.
If it opens, how do you know? If it shorts, your whole house is dark.
If I had to choose how to protect a computer, I'd choose a plug-in unit,
but I've never understood whether a $50 unit is better than a $15 unit.
As you say, the components are cheap.
I have heard that plug-in-units should be replaced every year or two
because they deteriorate. I don't know if that's true. It seems to me
that a well-designed unit can be trusted until the light comes on and
you can't get power.
When ice brought down a high-voltage line a few miles away, my
whole-house protector didn't save my TV or stereo. My scam plug-in
protector saved my computer, external drive, and modem.
It was a gusty day, and the woman across the street from them had
flickering at the same time, after which she had to restart her computer
and reset clocks.
The plug-in protector does nothing effective. A properly
sized protector should not vaporize or opens when shunting
typically destructive transients. If protector is vaporized,
then it provided ineffective protection.
Often an adjacent TV may suffer no damage, but the protector
fails catastrophically (catastrophic damage must never happen
to a protector as defined by MOV manufacturer data sheets).
Then the naive assume, "the protector sacrificed itself to
protect my TV". Reality: protector was so grossly undersized
as to fail while TV's internal protection protected the TV.
Remember, a transient confronts TV and protector at same time
with equal force. Protector does not sit between a transient
and TV - as myths claim. Protector connects to AC mains just
like another light bulb. But if the protector is undersized,
then some humans will speculate, "the protector failed to save
my TV". A transient too small to harm the TV instead
destroyed a grossly undersized (and overpriced) protector.
What kind of protection was that? Ineffective plug-in
protector was damaged by a transient too small to even harm
What does that human do? Buy more grossly undersized and
overpriced protectors - and recommend them to friends. A
properly sized protector means no one knows a transient
We install properly sized protectors so that failure is not
an issue. Protector is installed for events that occur
typically once every eight years. But to sell more $3 power
strips with some $0.10 components for $15 or $50, then I too
would hype a myth that protectors must be replaced every year.
Protectors degrade quickly when undersized. But again,
numbers expose the myth. Take a typical 345 joule plug-in
protector. Maybe it will last for two equally sized
transients. Therefore even the minimal 1000 joule 'whole
house' protector would last for maybe 300 of those same sized
transients. 2 verses 300. Protector installed for events
that occur typically once every eight years. Damning numbers
that reverse 100% your reasoning.
Increased joules causes an exponential increase in protector
life expectancy. So why are plug-in protectors so grossly
undersized? They are not providing effective protection. Why
waste more money on more $0.10 parts to properly size a
protector. If it fails, then the naive will hype "the
protector sacrificed itself to protection my...."
How do you know the 'whole house' protector did not save
appliances? Do you do as I do - identify the electrical path
AND replace all electrical components? How do you know that
plug-in protector did anything? What is the criteria? Again,
the old Missouri adage. Show me. What are the facts? Which
components did and did not fail? What was the complete
circuit of that transient?
In another example, the VCR may have shorted to protect an
adjacent TV. Then the naive human assumed a plug-in protector
provided the protection. But he could not explain why the VCR
was damaged. Turns out, the transient never saw the
protector. But again, this level of detail so often
demonstrates plug-in protectors as ineffective. How many
joules in each protector? Why are some so grossly undersized
as to be damaged? Just more damning numbers.
Then we have price. One spent $15 or $50 for ineffective
protection of each appliance. The properly sized 'whole
house' protector costs about $1 per appliance. Worries about
the 'whole house' protector shorting, not indicating a
failure, or leaving a house dark are not valid. Reasons why
involve details made obvious when the 'whole house' protector
A protector that catastrophically fails (vaporizes) is
classic of undersized protectors. But then where would you
want such a protector? On a desk full of papers, or in dust
balls on the rug behind a desk? Plug-in protectors are not
just undersized. They are in the wrong location for human
safety. Just more reasons why the plug-in protector is not
effective. The most damning reason - no earth ground which
means no effective protection.
Intermatic once provided a brochure describing an event in
their sales manager's house when Andrew went through Florida.
High voltage primary wire dropped on a wire into his house.
Intermatic 'whole house' protector was badly burned. But it
shunted the high voltage primary voltage until a utility fuse
finally cut off those thousands of volts. Nothing inside his
house was damaged. The house did not catch fire from
thousands of volts on 120 volt appliances. Plug-in protectors
did not vaporize while sitting on combustible materials inside
rooms. Properly sized 'whole house' protectors for about $1
per protected appliance? Or $15 to $50 for the grossly
undersized and ineffective plug-in protectors?
These are damning numbers. And then we add the most
important fact. The protector is only as effective as its
earth ground. Bottom line fact that plug-in protectors avoid
discussing to sell at 15 or 50 times the price.
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