Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!cbmvax!uunet!motcid!ahlenius From: ahlenius@motcid.UUCP (Mark Ahlenius) Newsgroups: sci.electronics Subject: Re: ANOTHER house wiring question (this one's basic) Message-ID: <5590@turquoise.UUCP> Date: 16 Jan 91 19:00:28 GMT References: <1948@umriscc.isc.umr.edu> Organization: Motorola Inc., Cellular Infrastructure Div., Arlington Heights, IL Lines: 72 robf@mcs213k.cs.umr.edu (Rob Fugina) writes: >In article mrapple@quack.sac.ca.us (Nick Sayer) writes: >>Now ground and neutral clearly are not the same thing. I would >>expect negative side effects were I foolish enough to hook >>a light bulb between hot and ground. Actually, the bulb will work fine. By using a pig tail lamp (100w) its a good idea to make sure that the bulb works fine between hot and ground - as this checks out the ground path to make sure it is a good connection. Note that is the circuit being tested is a gfi (ground fault interrupter) this will (should) cause the unit to trip. >Ground and neutral are exactly the same thing. If you were to trace the >wires back to your breaker box, you would find bare wires (ground) and white >wires (neutral) both connected to a grounding strip. The hot wire's potential >varies from ~170V above ground to ~170V below ground. The two wires that come >from the pole are both hot, BUT, the sine waves are 180 degrees out of phase >with one another, so when one is at +170, the other is at -170, and if you >connect something to those two, you will have a 340V sine wave. (values are >peak, not RMS...RMS would be about 120 and 240). If you check a copy of the NEC (National Electric Code) you will find out that neutral and ground are not the same thing. Note that these comments really only apply to the United States code. Yes it is true (at least in the Chicago area) that the neutral wire upon entrance to a building is to be "bonded" or tied to the chasis of the circuit panel. This is usually done via a small bonding lug that comes out of the neutral bus bar and gets connected to the chasis of the panel. A wire then connects from the neutral bus to the street side of the water pipe (if metallic) or to a series of ground stakes. This is the ONLY place that neutral and ground should be in common in the building. The emt (conduit) or bx sheath, or ground wire of romax (etc.) is not intended to be a normal current carrying circuit. It is there as a safety ground such that if an appliance fails (loose wire, meltdown, etc) the ground will short out the fuse or breaker and stop any further problems. The neutral wire is intended to be a normal current carrying circuit (is sometimes called the return path - although in a.c. its ...). If you attach a neutral wire to ground anywhere else in your building, you can create ground loops which I wont go into here. >MY QUESTION is, if you don't have 3-wire connections in your house, why >can't you connect the white wire to the ground lug and conuit/boxes, etc??? A very dangerous idea. Besides being illegal (against local and national codes) it could prove very dangerous. Many appliances (like washers & dryers) have their chasis tied to earth ground. If you tie the neutral wire to the ground lug on the outlet, you have essentially tied the chasis to neutral. Because the neutral wire is current carrying, it is possible that due to resistance in the wire (IR drop) and/or poor connections that a voltage drop may exist between the neutral at the outlet and your circuit panel. Now if someone (like a small child) brushes up against the chasis and happens (and it does happen) to touch a water pipe - a nice shock can be had! Electrical work is really pretty easy stuff. And because engineers and techs have an understanding of electronics - they often think that wiring a house is the same. The problem is that there are code laws out there to protect us from unforseen and misunderstood problems. If you are not aware of these practices - PLEASE contact someone who knows. Like a licenses (but not necessarily union) electrician. If you dont know what your doing, don't. -- =============== regards 'mark ============================================= Mark Ahlenius voice:(708)-632-5346 email: uunet!motcid!ahleniusm Motorola Inc. fax: (708)-632-2413 Arlington, Hts. IL, USA 60004