Notes on the Troubleshooting and Repair of Small Household Appliances and Power Tools


  16.16) Locating wires inside a wall

There are gadgets you can buy that look like test lights but sense the
electric field emitted by the Hot wire.  It is also possible to inject
a signal into the wire and trace it with a sensitive receiver.

However, if you are desperate, here is a quick and easy way that is worth
trying (assuming your wiring is unshielded Romex - not BX - and you can power
the wire).  Everything you need is likely already at your disposal.

Get a cheap light dimmer or a fixture with a light dimmer (like that halogen
torchier that is now in the attic due to fire safety concerns) and plug it
into an outlet on the circuit you want to trace.  Set it about half brightness.

Now, tune a portable AM radio in between stations.  If you position the
radio near the wire, you should hear a 120 Hz hum - RFI (Radio Frequency
Interference) which is the result of the harmonics of the phase controlled
waveform (see the section: "Dimmer switches and light dimmers".  Ironically,
the cheaper the dimmer, the more likely this will work well since no RFI
filtering is built in.

I have tried this a bit and it does work though it is somewhat quirky.  I do
not know how sensitive it is or over how large a circuit it is effective.
It is somewhat quirky and even normal power may have enough junk on the 
waveform to hear it in the radio.  However, with a partner to flip the dimmer
off and on to correlate its position with what you hear, this may be good

  16.17) Bad Neutral connections and flickering lights or worse

Residential service comes from a centertapped 110-0-110 V transformer on the
utility pole.  There are 3 wires into your house - 2 Hot or live wires and the
Neutral which is the centertap of the transformer.  If the connection between
the Neutral bus in your service panel and the pole transformer centertap
becomes loose and opens or develops a high resistance, then the actual voltage
on either of the Hots with respect to the Neutral bus (which is divided among
your branch circuits) will depend on the relative loads on either side much in
the way of a voltage divider using resistors.  Needless to say, this is an
undesirable situation.

Symptoms include excessive flickering of lights (particularly if they get
brighter) when large appliances kick in, light bulbs that seem too bright
or too dim or burn out frequently, problems with refrigerators or freezer
starting due to low voltage, etc.  In the worst case, one set of branch
circuits can end up with a voltage close to 220 VAC - on your poor 110 V
outlets resulting in the destruction of all sorts of appliances and
electronics.  The opposite side will see a much reduced voltage which may be
just as bad for some devices.

It is a simple matter for an electrician to tighten up the connections but
this is not for the DIY'er unless you are familiar with electrical wiring and
understand the implications of doing anything inside the service panel while
it is live!

  16.18) Lightning storm trips GFCIs protecting remote outdoor outlets

"I have several outdoor 110V outlets, protected by GFCI breakers. These
 circuits nearly always trip when there are nearby lightening strikes.
 I am satisfied that there is no short circuit caused by water as :

 * A lightning storm without rain will still trip the GFCI.

 * Water from the sprinklers does not cause a problem.

 * I can immediately reset the GFCI when it is still raining and it comes
   back on.

 The electrical cables buried underground run for about 600 feet.

 Is GFCI tripping caused by electrical storms normal ? Are my GFCI breakers too
 sensitive ? Is there any way to modify the circuits to avoid this?"

This doesn't surprise me.  Long runs of cable will be sensitive to the
EM fields created by nearby lightning strikes.  Those cables probably
have 3 parallel wires: H, N, G.  The lightning will induce currents in 
all three which would normally not be a problem as long as H and N are
equal.  However, I can see this not being the case since there will be
switches in the Hot but not the Neutral so currents could easily unbalance.

These are not power surges as such and surge suppressors will probably not

Since it happens with all of your GFCIs, it is not a case of a defective unit.
Perhaps there are less sensitive types but then this would reduce the
protection they are designed to provide.

  16.19) GFCI trips when it rains (hard)

Most likely, moisture/water is getting into some portion of the GFCI's
protected wiring (at the GFCI or anywhere downstream) and the GFCI is
simply doing its job.  You will have to trace the wiring through all
junction boxes and outlets to determine where the problem is located.
Yes, I know this may not be your idea of fun!

  16.20) Why a GFCI should not be used with major appliances

A Ground Fault Circuit Interrupter is supposed to be a valuable safety
device.  Why not use them everywhere, even on large appliances with
3 wire plugs?

1. A properly grounded 3 prong outlet provides protection for both people
   and the appliance should a short circuit develop between a live wire
   and the cabinet.

2. Highly inductive loads like large motors or even fluorescent lamps or
   fixtures on the same circuit can cause nuisance tripping of GFCIs which
   needless to say is not desirable for something like a refrigerator.

  16.21) Toasters and GFCIs

The following is a reason to use GFCIs on kitchen outlets that may not
be obvious:

(From: David Buxton (David.Buxton@tek.com)).

In addition to the usual explanations dealing with safety around water,
another reason why kitchen outlets need a GFCI is the toaster.  All too 
often people stick a butter knife in there to dislodge some bread.  If 
the case was grounded there would be short from the element to the case. 
So toasters are two wire instead of 3-pronged.  So, you must have a GFCI 
for any outlet that might take on a toaster.

  16.22) Reverse polarity outlets - safety and other issues

"Our new home has reverse polarity in all of the electrical outlets.  The
 house inspector didn't seem to think this was a major problem, and neither
 did he think it was worth fixing.  Can anyone explain how this might matter
 for us?  The best I understand this is that when something is plugged in, even
 when it's not turned on, there is  still a current going through it--is that
 true at all, or is that normal?  Our biggest concern is our computers, and the
 possibility that our surge protectors won't be effective.  If anyone could
 clear this up, that would be great."

New as in brand new or new for you?  If it is a totally new home, the builder
should have them fixed and you should not sign off on the house until this is
done.  While there is no imminent danger, the house inspector was being a bit
too casual for my tastes.  It is not a big deal as in should stop you from
going through with the purchase but it really should be fixed.

As far as current present when the appliance is off, this is not quite true.
When properly wired, the power switch is the first thing in the circuit so it
cuts off power to all other parts of the internal wiring.  With the reversal,
it is in the return - the rest of the wiring will be live at all times.  Except 
or servicing, this is really not that big a concern and does not represent any
additional electricity usage.

Normally (I assume these are 3 prong grounded outlets) you have the following:

* Hot - the live conductor - the narrow slot.
* Neutral - the return for the current used by the device - the wide slot.
* Ground (or safety ground) - the U shaped slot.

Reverse polarity means that Hot and Neutral are interchanged. (any other
variation like an interchange with the ground represents a serious safety
hazard and it should be corrected as soon as possible.  The outlet should
not used until it is).

For most appliances and electronics, this does not really matter.  By
design, it must not represent a safety hazard.  However, there can be
issues - as you are concerned - with surge suppressors and susceptibility
to interference.  In some cases, the metal case of a stereo could be
coupled to the Neutral by a small capacitor to bypass radio frequency
interference.  This will be coupled now to Hot instead.  While not a
safety hazard, you might feel an almost imperceptible tingle touching
such a case.

Surge suppressors may or may not be affected (to the extent that they are
ever effective in any case - unplugging the equipment including modem lines
and the like during an electrical storm is really the only sure protection
but that is another section).  It depends on their design.  Some handle the
3 wires in an identical manner and interchanging them makes no difference.
Others deal differently with the Hot and Neutral in which case you may lose
any protection you would otherwise have.

My advice: If you are handy electrically, correct them yourself.  If not,
get them corrected the next time you have an electrician in for any reason.
It is a 5 minute job per outlet unless the wiring is extremely screwed up.

Use a properly wired outlet for your computer to be doubly sure.

It is not an emergency but I consider proper wiring to be very desirable.

Here is another example:

"I was checking some outlets in my apartment. As I recall, the narrow prong
 should be hot, i.e., there should be 120 V between it and the wide prong or
 the ground prong. The wide prong should be neutral, i.e., it should show no
 voltage relative to the ground prong. Well, it appears that the Neutral
 and Hot wires are reversed in some outlets. In others, they are correct."

Well, there should be very little voltage although it may not be 0.

Reversed polarity outlets are not unusual even in new construction.

Reversed H and N is not usually dangerous as appliances must be designed
so that no user accessible parts are connected to either H or N - even
those with polarized plugs.  Think of all the times people use such appliances
in old unpolarized outlets or with unpolarized extensions cords.  (There are
exceptions like electric ranges where there may be no separate safety ground
conductor but I assume you are talking about branch circuits, not permanently
wired-in appliances.)

"In still others, I get some voltage between ground and either the wide or
 narrow prong. Ack. Should I worry? Should I do more than worry?"

You should, of course, measure full line voltage between the H and G.  The
safety ground, G, does not normally carry any current but is at the same or
nearly the same potential as N.

The voltage between G and (actual) N if quite low - a couple volts or less - is
probably just due to the the voltage drop in the current carrying N wire.  Turn
off everything on this branch circuit and it should go away.  However, there
could also be a bad (high resistance connection) somewhere in the N circuit.

If the voltage reads high to either H or N - say, 50 volts - and you are
measuring with a high impedance multimeter, this is probably just due to an
open ground: a three prong outlet was installed without connecting the ground
(in violation of Code unless on a GFCI) and this leakage is just due to
inductive/capacitive pickup from other wires.

Full line voltage on the G conductor relative to an earth ground (like a
copper cold water pipe) would represent a serious shock hazard to be corrected
as soon as possible - the appliance or outlet should *not* be used until
the repair is made.  While unlikely, for anyone to screw up this badly, it
could happen if someone connected the green or copper wire, or green screw
to H instead of G.

In any case, it would be a good idea to correct the H-N reversals and determine
if the voltage on the G is an actual problem.

  16.23) Comments on whole house surge suppressors

These are typically offered your power company:

"I have a surge suppressor that was put between my meter and the service
 panel.  It's rented from my power company.  The advertised product is part of
 a 'package' that includes plug in surge suppressors.  The package price is
 $4.95/month.  I didn't want the plug in suppressors so they said that it
 would be $2.75/month.  Is this a good deal?"

(From: Kirk Kerekes (redgate@oklahoma.net)).

The power company just passes on the warranty of the manufacturer, which
is, in turn, merely an insurance policy whose premium in included in the
normal retail price of the unit. Basically, the power company is taking a
product with a wholesale cost of about $30, and "renting" it to consumers
for $40-$100 a year. 


Nice work if you can get it.

Note that most homeowner and similar insurance policies _already_ cover
lightning damage, and that the policy from the surge protector is
generally written to only apply to losses not already covered by other
insurance.  As a result, you are paying for insurance that you will likely
*never* be able to make a claim against, even if the device is totally

The simplest whole-house protection is to purchase an Intermatic whole
house surge protector ($40 from Home Depot or Lowe's) and install it
yourself (or pay an electrician to do so -- maybe 15 minutes of work).
Then purchase inexpensive ($10 and under) plug-in surge protectors and
surge-protected power strips and use them all over the house at sensitive
equipment. Note that surge protectors and surge protected power strips
protect the _other_ outlets in the house as well as the ones they contain
(because the MOV's in inexpensive surge protectors are simply connected in
parallel with the power line), so the more of that that you have plugged
in, the more effectively protected your home is. Some power strips need to
be turned "on" for the MOV's to be connected to the power lines.

You can also buy MOV's and add your own custom protection -- but if you
don't already know that, you probably shouldn't be tinkering with such

Note that you should only purchase surge protectors that contain a monitor
LED to tell you if the protector is still functioning -- MOV's deteriorate
when zapped by large surges. This is one reason why I recommend the
multiple-power-strip distributed-protection approach -- it is doubtful
that all of your surge protectors/power strips will get zorched at once.

Chapter 17) All About Wire and the AWG (American Wire Gauge) Numbers

  17.1) Some types of wire

Note: For an understanding of the AWG numbers, you may want to first see the
section: "American Wire Gauge (AWG) table for annealed copper wire".

A semi-infinite variety of wire and cable is used in modern appliances,
electronics, and construction.  Here is a quick summary of the buzz words
so you will have some idea of what your 12 year old is talking about!

* Solid wire: The current carrying conductor is a single solid piece of metal
  (usually copper.  It may be bare, tinned (solder coated), silver plated, or
  something else.

  Solid wire may be used for general hookup inside appliances and electronics,
  and building (and higher power wiring) but not for cords that need to be
  flexible and flexed repeatedly.

* Stranded wire: The current carrying conductor consists of multiple strands
  of copper or tinned copper (though other metals may be found in some cases).
  The individual strands are NOT insulated from one-another.  The wire gauge
  is determined by the total cross sectional area (which may be a bit greater
  than the specified AWG number due to discrete number of strands).  See the
  section: "What about stranded wire?".

  Stranded wire is used for general hookup, building wiring, etc.  It is
  easier to position than solid wire (but tends not to stay put) and more
  robust when flexed repeatedly.  Cordsets always use finely stranded wire
  but despite this, may develop problems due to flexing after long use.

* Magnet wire: This is a solid copper (or sometimes aluminum or silver)
  conductor insulated with a very thin layer of varnish or high-tech plastic.
  This coating must be removed either chemically, by heating in a flame, or
  fine sandpaper, before the wire can be connected to anything.

  Magnet wire is used where a large number of turns of wire must be packed as
  tightly as possible in a limited space - transformers, motors, relays,
  solenoids, etc.

  The very thin insulation is susceptible to nicks and other damage.

* Litz wire: This is similar to stranded wire EXCEPT that the strands are
  individually insulated from each other (like multiple pieces of magnet

  Litz wire is used in high frequency transformers to reduce losses (including
  the skin effect which results in current only traveling near the surface
  of the wire - using multiple insulated strands increases its effective
  surface area).

  Like magnet wire, the insulation needs to be removed from all strands before
  making connections.

* Tinsel wire: A very thin, metallic conductor is wound around a flexible
  cloth or plastic core.

  Tinsel wire is found in telephone and headphone cords since it can be made
  extremely flexible.

  Repair is difficult (but not impossible) since it very fine and the
  conductor must be unraveled from the core for soldering.  The area of the
  repair must be carefully insulated and will be less robust than the rest of
  the cord.

* Shielded wire: An insulated central conductor is surrounded by a metal braid
  and/or foil shield.

  Shielded wire is used for low level audio and video, and other analog or
  digital signals where external interference needs to be minimized.

* Coaxial cable: This is similar to shielded wire but may be more robust and
  have a specified impedance for transmitting signals over long distances.

* Zip cord: This is 2 or 3 (or sometimes more) conductor cable where the
  plastic insulation is scored so that the individual wires can be easily
  separated for attachment to the plug or socket.

* 14/2, 12/3, etc.: These are the abbreviations used for building (electrical)
  wire like Romex (which is one name brand) and for round or zip-type cordset
  wire.  The conductor material is usually copper.

  Note: Some houses during the '50s and '60s were constructed with aluminum
  wiring which has since been found to result in significantly increased risk
  of fire and other problems.  For more information, see the references listed
  in the section: "Safe electrical wiring".  However, aluminum wiring is safe
  if installed according to very specific guidelines (and is used extensively
  in power transmission and distribution - probably for your main connection
  to the utility - due to its light weight and low cost).

  The first number is the AWG wire gauge.

  The second number is the number of insulated conductors (excluding any bare
  safety ground if present).  For example:

  - A 14/2 Romex cable has white and black insulated solid #14 AWG current
    carrying conductors and a bare safety ground (some older similar types of
    cable had no safety ground, however).

  - A 16/3 cordset has white, black and green insulated stranded #16 AWG wires
    (or, overseas, blue, brown, and green or green with yellow stripe).

  17.2) So, where did AWG come from?

Nearly everyone who has done any sort of wiring probably knows that the AWG or
American Wire Gauge number refers to the size of the wire somehow.  But how?

(From: Frank (fwpe@hotcoco.infi.net)).

According to the 'Standard Handbook for Electrical Engineers' (Fink and Beaty)
the 'gauge' you referenced to is 'American Wire Gauge' or AWG and also known
as Brown & Sharp gauge.

According to above handbook, the AWG designation corresponds to the number of
steps by which the wire is drawn. Say the 18 AWG is smaller than 10 AWG and is
therefore drawn more times than the 10 AWG to obtain the smaller cross
sectional area.  The AWG numbers were not chosen arbitrary but follows a
mathematical formulation devised by J. R. Brown in 1857!

  17.3) For the marginally mathematically inclined

Each increase of 3 in the gauge halves the cross sectional area.  Each
reduction by 3 doubles it.  So, 2 AWG 14 wires is like one AWG 11.

It seems that everyone has their own pet formula for this (though I prefer
to just check the chart, below!).

(From: Tom Bruhns (tomb@lsid.hp.com)).

As I understand it, AWG is defined to be a geometric progression with AWG 0000
defined to be 460 mils diameter and 36 gauge defined to be 5.000 mils diameter.
This leads directly to the formula:

              Diameter(mils) = 5 * 92^((36-AWG)/39)

That is, 460 mils is 92 times 5 mils, and the exponent accounts for 39 steps
of AWG number starting at 36 gauge.

(From: David Knaack (dknaack@rdtech.com)).

You can get a fairly accurate wire diameter by using the equation:

          Diameter(inches) = 0.3252 * e^(-0.116 * AWG)

where 'e' is the base of the natural logarithms, 2.728182....

I don't know where it came from, but it is handy (more so if you can do natural
base exponentials in your head).

In its simplest form, the cross sectional area is:

                 A(circular mils) = 2^((50 - AWG) / 3)

  17.4) American Wire Gauge (AWG) table for annealed copper wire

(Similar tables exist for other types of wire, e.g., aluminum.)

(Table provided by: Peter Boniewicz (peterbon@mail.atr.bydgoszcz.pl)).

Wire Table for AWG 0000 to 40, with diam in mils, circular mils,
square microinches, ohms per foot, ft per lb, etc.

   AWG  Dia in  Circ.  Square  Ohm per lbs per Feet/   Feet/    Ohms/
  gauge  mils   Mils   MicroIn 1000 ft 1000 ft Pound    Ohm     Pound
  0000  460.0  211600  166200  0.04901 640.5   1.561   20400   0.00007652
  000   409.6  167800  131800  0.06180 507.9   1.968   16180   0.0001217
  00    364.8  133100  104500  0.07793 402.8   2.482   12830   0.0001935

  0     324.9  105500  82890   0.09827 319.5   3.130   10180   0.0003076
  1     289.3  83690   65730   0.1239  253.3   3.947   8070    0.0004891
  2     257.6  66370   52130   0.1563  200.9   4.977   6400    0.0007778

  3     229.4  52640   41340   0.1970  159.3   6.276   5075    0.001237
  4     204.3  41740   32780   0.2485  126.4   7.914   4025    0.001966
  5     181.9  33100   26000   0.3133  100.2   9.980   3192    0.003127

  6     162.0  26250   20620   0.3951  79.46   12.58   2531    0.004972
  7     144.3  20820   16350   0.4982  63.02   15.87   2007    0.007905
  8     128.5  16510   12970   0.6282  49.98   20.01   1592    0.01257

  9     114.4  13090   10280   0.7921  39.63   25.23   1262    0.01999
  10    101.9  10380   8155    0.9989  31.43   31.82   1001    0.03178
  11    90.74  8234    6467    1.260   24.92   40.12   794     0.05053

  12    80.81  6530    5129    1.588   19.77   50.59   629.6   0.08035
  13    71.96  5178    4067    2.003   15.68   63.80   499.3   0.1278
  14    64.08  4107    3225    2.525   12.43   80.44   396.0   0.2032

  15    57.07  3257    2558    3.184   9.858   101.4   314.0   0.3230
  16    50.82  2583    2028    4.016   7.818   127.9   249.0   0.5136
  17    45.26  2048    1609    5.064   6.200   161.3   197.5   0.8167

  18    40.30  1624    1276    6.385   4.917   203.4   156.6   1.299
  19    35.89  1288    1012    8.051   3.899   256.5   124.2   2.065
  20    31.96  1022    802.3   10.15   3.092   323.4   98.50   3.283

  21    28.46  810.1   636.3   12.80   2.452   407.8   78.11   5.221
  22    25.35  642.4   504.6   16.14   1.945   514.2   61.95   8.301
  23    22.57  509.5   400.2   20.36   1.542   648.4   49.13   13.20

  24    20.10  404.0   317.3   25.67   1.223   817.7   38.96   20.99
  25    17.90  320.4   251.7   32.37   0.9699  1031.0  30.90   33.37
  26    15.94  254.1   199.6   40.81   0.7692  1300    24.50   53.06

  27    14.20  201.5   158.3   51.47   0.6100  1639    19.43   84.37
  28    12.64  159.8   125.5   64.90   0.4837  2067    15.41   134.2
  29    11.26  126.7   99.53   81.83   0.3836  2607    12.22   213.3

  30    10.03  100.5   78.94   103.2   0.3042  3287    9.691   339.2
  31    8.928  79.70   62.60   130.1   0.2413  4145    7.685   539.3
  32    7.950  63.21   49.64   164.1   0.1913  5227    6.095   857.6

  33    7.080  50.13   39.37   206.9   0.1517  6591    4.833   1364
  34    6.305  39.75   31.22   260.9   0.1203  8310    3.833   2168
  35    5.615  31.52   24.76   329.0   0.09542 10480   3.040   3448

  36    5.000  25.00   19.64   414.8   0.07568 13210   2.411   5482
  37    4.453  19.83   15.57   523.1   0.06001 16660   1.912   8717
  38    3.965  15.72   12.35   659.6   0.04759 21010   1.516   13860

  39    3.531  12.47   9.793   831.8   0.03774 26500   1.202   22040
  40    3.145  9.888   7.766   1049.0  0.02993 33410   0.9534  35040
  41    2.808  7.860   6.175   1319    0.02379 42020   0.758   55440

  42    2.500  6.235   4.896   1663    0.01887 53000   0.601   88160
  43    2.226  4.944   3.883   2098    0.01497 66820   0.476   140160
  44    1.982  3.903   3.087   2638    0.01189 84040   0.379   221760

  45    1.766  3.117   2.448   3326    0.00943 106000  0.300   352640
  46    1.572  2.472   1.841   4196    0.00748 133640  0.238   560640

Ohms per 1000 ft, ft per Ohm, Ohms per lb, all taken at 20 degC (68 degF).

Note: Values for AWG #41 to #46 extrapolated from AWG #35 to #40 based on wire
gauge formula.

  17.5) What about stranded wire?

(From: Calvin Henry-Cotnam (cal@cate.ryerson.ca)).

In addition to the cross-section area, there are a few other factors.  First
off, a stranded wire effectively has more surface area than a solid wire of
the same gauge, but much of this surface is "inside" the wire.

I checked out the label of a spool of #18 stranded wire and found it was
comprised of 16 strands of #30 wire.  Given the info above that each reduction
of 3 in the gauge, then #18 has a cross-section area that is 16 times greater
than #30 -- so it *appears* to translate exactly.

Looking through a catalog for wire, I found that this more-or-less holds true,
though the occasional wire might have an extra strand or two.  Here is what I
quickly found -- there are many more, but this is a sample:

  17.6) Overall gauge Typical stranded wires made up of

            #32              7 x #40
            #30              7 x #38
            #28              7 x #36
            #26              7 x #34
            #24              7 x #32    19 x #36
            #22              7 x #30    19 x #34
            #20              7 x #28    10 x #30    19 x #32
            #18             16 x #30
            #16             19 x #29    26 x #30
            #14             41 x #30
            #12             65 x #30
            #10             65 x #28
             #8             84 x #27

Chapter 18) Items of Interest

Editor's note: Not all of these actually apply to small appliances but may
be of use nonetheless.

  18.1) Determining electricity usage

So, where does all the electricity (or money, same thing) go?

You could put a watt-hour meter on every appliance in your house but that is
probably not needed to estimate the expected electricity usage.

Check the nameplate on heating appliances or those with large motors.  They
will give the wattage.  Multiple these by hours used and the result is W-hours
(or KW-hours) worst case.  Appliances that cycle like refrigerators and space
heaters with thermostats will actually use less than this, however.

Multiple light bulb wattages by hours used to get the W-hours for them.

Things like radios, clocks, small stereos, etc., are insignificant.

Add up all the numbers :-).

It would be unusual for an appliance to suddenly increase significantly in its
use of electricity though this could happen if, for example, the door on a
freezer or refrigerator is left ajar or has a deteriorated seal.

  18.2) Taking equipment overseas (or vice-versa)

When does it make sense to take an appliance or piece of electronic equipment
to a country where the electric power and possibly other standards differ?

For anything other than a simple heating appliance (see below) that uses a
lot of power, my advise would be to sell them and buy new when you get there.
For example, to power a microwave oven would require a 2KVA step down (U.S.
to Europe) transformer.  This would weigh about 50 pounds and likely cost
almost as much as a new oven.

There are several considerations:

1. AC voltage - in the U.S. this is nominally 115 VAC but in actuality
   may vary from around 110 to 125 VAC depending on where you are located.
   Many European countries use 220 VAC while voltages as low as 90 or 100
   VAC or as high as 240 VAC (or higher?) are found elsewhere.

2. Power line frequency - in the U.S. this is 60 Hz.  The accuracy,
   particularly over the long term, is excellent (actually, for all intents
   and purposes, perfect) - better than most quartz clocks.  In many foreign
   countries, 50 Hz power is used.  However, the stability of foreign power
   is a lot less assured.

3. TV standards - The NTSC 525L/60F system is used in the U.S. but other
   countries use various versions of PAL, SECAM, and even NTSC.  PAL
   with 625L/50F is common in many European countries.

4. FM (and other) radio station channel frequencies and other broadcast
   parameters differ.

5. Phone line connectors and other aspects of telephone equipment may differ
   (not to mention reliability in general but that is another issue).

6. Of course, all the plugs are different and every country seems to think
   that their design is best.

For example, going to a country with 220 VAC 50 Hz power from the U.S.:

For electronic equipment like CD players and such, you will need a small
step down transformer and then the only consideration power-wise is the
frequency.  In most cases the equipment should be fine - the power
transformers will be running a little closer to saturation but it is
likely they are designed with enough margin to handle this.  Not too
much electronic equipment uses the line frequency as a reference for
anything anymore (i.e., cassette deck motors are DC).

Of course, your line operated clock will run slow, the radio stations
are tuned to different frequencies, TV is incompatible, phone equipment
may have problems, etc.

Some equipment like PCs and monitors may have jumpers or have universal
autoselecting power supplies - you would have to check your equipment
or with the manufacturer(s).  Laptop computer, portable printer,  and
camcorder AC adapter/chargers are often of this type.  They are switching
power supplies that will automatically run on anywhere from 90-240 VAC,
50-400 Hz (and probably DC as well).

Warning: those inexpensive power converters sold for international travel
that weigh almost nothing and claim to handle over a kilowatt are not
intended and will not work with (meaning they will damage or destroy)
many electronic devices.  They use diodes and/or thyristors and do not
cut the voltage in half, only the heating effect.  The peak voltage may
still approach that for 220 VAC resulting in way too much voltage on the
input and nasty problems with transformer core saturation. For a waffle
iron they may be ok but not a microwave oven or stereo system.  I also
have serious doubts about their overall long term reliability and fire
safety aspects of these inexpensive devices..

For small low power appliances, a compact 50 W transformer will work fine
but would be rather inconvenient to move from appliance to appliance or
outlet to outlet.  Where an AC adapter is used, 220 V versions are probably
available to power the appliance directly.

As noted, the transformer required for a high power heating appliance is
likely to cost more than the appliance so unless one of the inexpensive
converters (see above) is used, this may not pay.

For additional information, see the document: "International Power and
Standards Conversion".

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Written by Samuel M. Goldwasser. | [mailto]. The most recent version is available on the WWW server http://www.repairfaq.org/ [Copyright] [Disclaimer]