All About Circuits Forum  

Go Back   All About Circuits Forum > Electronics Forums > General Electronics Chat

Notices

General Electronics Chat Discussion forum for general chat about anything electronics related, including asking questions about material in the All About Circuits E-book, Worksheets, and Videos.

Reply   Post New Thread
 
Thread Tools Display Modes
  #1  
Old 08-27-2006, 01:14 AM
coolbreeze coolbreeze is offline
New Member
 
Join Date: Aug 2006
Posts: 1
Default hot common????

my boss and i have been having a disagreement, about the common wire in a three wire split phase 240 a.c. circuit. the argument is , first , that the neutral wire and common wire is one in the same.. second, that this wire is only used for return voltage and is never a live wire... he says that is he taks a voltage reading from the wires connecting to the capacitor wich are ( fan , commmon , compressor) he says if he takes a voltage reading from one of the legs and the common wire he gets 240 volts, therfore he believes the common is a hot wire..
can you please explain this to me .. and also explain that the common and neutral wire is the same thing... thanks.......
Reply With Quote
  #2  
Old 08-27-2006, 01:44 AM
beenthere's Avatar
beenthere beenthere is offline
Senior Member
 
Join Date: Apr 2004
Location: Missouri, USA (GMT -6)
Posts: 15,815
Blog Entries: 10
Default

Hi,

AC common and neutral are equivalent terms. It is not live. It is for the return of current in the circuit.

A voltmeter measures a voltage difference between two points. If you see 240 volts between any phase and neutral, then it follows that the neutral is at ground potential. If it were live, there would be a lesser voltage differnce between it and the voltage leg being metered. If you have an earth ground close by, place the meter leads on it and neutral, and see what voltage shows up.
Reply With Quote
  #3  
Old 08-28-2006, 05:40 AM
Joe S. Joe S. is offline
Junior Member
 
Join Date: Aug 2006
Posts: 10
Default May I intrude?

please see my comments to this link:http://forum.allaboutcircuits.com/showthread.php?t=3159
It has some application here.
If the neutral is carrying current then you need a safety ground, example a split phase welder might have a 120v wire feeder attachment, then it requires a safety ground, whereas a compressor may not have an active neutral and likely would not, but if that neutral is carrying load then a seperate safety ground is required. same deal with 3 phase, it's no longer permitted to run 3 wire 3 phase here anymore. Bottom line error in the favor of safety, money is replaceable, lives are not.
Reply With Quote
Reply   Post New Thread

Tags
,


Related Site Pages
Section Title
Worksheet Delta and Wye 3-phase circuits
Worksheet Multi-stage transistor amplifiers
Worksheet AC motor theory
Textbook Three-phase power systems : Polyphase Ac Circuits
Textbook Single-phase power systems : Polyphase Ac Circuits
Textbook Special transformers and applications : Transformers
Worksheet Safety grounding
Textbook Wiring Color Codes : Color Codes
Textbook Safe circuit design : Electrical Safety
Textbook Safe meter usage : Electrical Safety


Similar Threads
Thread Thread Starter Forum Replies Last Post
Common Base problem Kubbe Homework Help 7 11-26-2006 02:19 PM
OP AMPS... Common Mode Input Range Inquiry jvp0378 General Electronics Chat 3 11-01-2006 06:23 AM
common base amplifier definition boom General Electronics Chat 8 10-25-2006 05:43 PM
feedback topologies? majinboy Homework Help 5 06-29-2006 01:43 AM
Common mode voltage Coz General Electronics Chat 1 05-14-2005 04:05 PM

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT. The time now is 09:23 PM.


User-posted content, unless source quoted, is licensed under a Creative Commons Public Domain License.
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.