Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!apple!mailcom!Ploni.Almoni
From: Ploni.Almoni@mailcom.FIDONET.ORG (Ploni Almoni)
Newsgroups: sci.electronics
Subject: Re: Flakey Power?
Message-ID: <4061.24964BEF@mailcom.FIDONET.ORG>
Date: 13 Jun 89 13:16:32 GMT
Organization: MailCom Public USENET, Palo Alto CA (415) 855-9548
Lines: 47

Don -   re your problem of "outlet voltage" varying from 100 - 150 V
  
This is a well known, SERIOUS and DANGEROUS problem.  It is NOT good
for the power supply and will eventually lead to premature and
catastrophic failure.  To say nothing of what the line surges will do
to your data!!
  
It is caused by an ungrounded neutral - a code violation as well as a
safety hazard.
  
In a 120/240 V service, the power utility supplies 120 V each side of
a grounded neutral. This grounded neutral (the "white wire" in the
cable or the "elongated slot" in the outlet) is supposed to be a
solid, reliable connection and extended throughout the installation. 
  
However, if the neutral in the particular circuit (group of outlets,
for instance) becomes isolated from the entrance grounded neutral, the
120 V loads stacked in series between the two "hot" lines will not
receive 120 V.  What they will receive between the "hot" line and the
UNgrounded neutral depends on the balance of the loads between the two
"sides" of the 240/120 circuit - in that case the only "given" is the
240 V "line-to-line".  If the loads are balanced, the line-to-neutral
voltages will be approximately correct.  If the loads are unbalanced,
one side will get a high voltage while the other will get a low
voltage.  And as the balance shifts (as stuff is turned on and off,
for instance), the voltage will go up and down.  90/150 V is not
unusual.
  
This problem has been the cause of an awful lot of "appliance frying"
over the years.  It also results in improper operation ( = failure to
protect) of Ground Fault Interrupters, a specific safety device.  And
it can cause shock hazards on equipment plugged into those lines.
  
QUICK - get the house electrician to check the breaker panels and
entrance equipment to see if a "white wire" has broken or come loose
from the neutral bus.
  
Your computer's life - or YOUR life - may depend on it.
  
          -=Ploni=-  
  
  



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