House wiring? (slightly off-topic)

[J. Larry Hendry]

Andrew,

As others have pointed out, the first thing to do is to check voltage.  In
the USA, standards require voltage delivered to the meter base to be between
114 and 126 volts AC  RMS.   Since your house is only 18 years old, it is
surely equipped with 240 volt wiring which means that your mains supply is
actually two 120 volt legs, 180 degrees out of phase.  So, you have 3
wires -- hot 1, hot 2, and neutral.  The neutral is required to have one
earth connection at the meter base.  So you voltage should be ~ 120 volts
hot1 to neutral, ~ 120 volts hot2 to neutral, and ~ 240 volts hot1 to hot2.
Some of the 120 volt loads in your house are connected between hot leg1 and
neutral, and some are connected between hot leg2 and neutral.  Obviously,
240 volt loads are connected hot 1 to hot 2.

Although this explanation may seem elementary, it is essential to
understanding the # 1 cause of high voltage in residential 120 - 240 volt
service, and to determining whether the trouble is yours or the power
company's  When you check your voltage, be certain to check at a variety of
locations , including 240 volts outlets if you have them.  BE CAREFUL.  I
work on a routine basis with voltages over 1/2 million volts and I can tell
you that the majority of fatalities occur with voltages less than 600.

If you find ALL of the voltage high, the trouble is most certainly that of
your power company.  Anything above 126-126-252 violates USA standards.
However, you may find that one of the 120 volt hot legs appears high, and
one 120 volt hot leg appears low while the 240 appears about normal.  In
this case there is a bad neutral connection.  In all the years of sending
trouble shooters out to customer homes for high voltage complaints, open or
poor neutral connections have been the most commonly found trouble.  Often,
the loads are not balanced between hot legs.  If the neutral connection is
missing, the mains neutral is supplied only from earth through your meter
base connection.  While this may work, the high impedance earth connection
will give you trouble when loads are unbalanced (which is typical).  More
loads on hot1 cause that hot1 to neutral voltage to collapse which pushes up
the hot2 to neutral voltage.  So, the customer is normally experiencing high
and low voltage at the same time.  However, if the excursions are not
severe, they tend to notice the high and not the low.  I will add that most
of the time, we have found the neutral connection to be bad on the utility
side or in the customer's meter base.

Global disclaimer:  I know this is different outside the USA, and I know
that in the USA there are a huge variety of different service voltages
available.  So, understand this does not apply to all.  However, it does
describe the normal 240 volt, center-tapped USA single-phase residential
delivery standard.

Larry Hendry
S-DIY newbie, high voltage by profession.


----- Original Message -----
From: <IXQY at aol.com>
To: <synth-diy at node12b53.a2000.nl>
Sent: Wednesday, December 27, 2000 7:45 AM
Subject: House wiring? (slightly off-topic)


 I moved into an 18 year old house a little more than a year ago. In this
house, I have a problem with light bulbs burning out really often. I
probably
replace anywhere from one to five light bulbs a month (!). This is
throughout
the house and is not limited to one or two light sockets. It also happens
throughout the year, so I don't think it's related to my central AC unit,
which I previously had thought.  Some light bulbs go out as I'm turning them
on and others go out while they are already on.