House wiring? (slightly off-topic)

[Magnus Danielson]

From: "J. Larry Hendry" <jlarryh at iquest.net>
Subject: Re: House wiring? (slightly off-topic)
Date: Wed, 27 Dec 2000 12:42:01 -0600

> Andrew,

Hi Larry,

> 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.

Um, those 240 Volt outlets that you have these days, do they happend
to be European style outlets? Have they started to appear at all? Just
curious.

BTW, as you migth know Europe is (supposed to be) normalized around
230V by now.

> 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.

Humm... how is power distributed to households in the USA? In Sweden I
think almost all are given a 400 V three-phase with ground wire. The
zero and protective ground is wired together to the ground wire in the
meter/distribution central of the household. It would be interesting
to get somewhat enligthend on how the American setup looks.

> 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.

This two-phase system that you got, where is the transition between
three-phase (distribution network) and two-phase occur?

Cheers,
Magnus