Whether a case needs to be grounded or not is up in the air, but whether or not the case should be left plugged into the wall is not. This is simply just not a good practice. The chances of being hurt or killed are very, very small, but finite. Why take that chance at all? If you feel that you need to ground your case, I suggest that you purchase a three-into-two cheater plug. Plug your computer cord into the cheater plug and connect the green grounding wire to a well-grounded water pipe. This will safely ground your computer with no risk of hurting yourself. (Of course, if there is a lightning storm going on, then you should not even do this!) You could also just connect your case to a pipe using alligator clips and a wire. The pipe must be grounded - no plastic pipes between your connection and the ground. The main point that I have been trying to convey is that the "ground" on the wall socket is not necessarily at earth ground, nor is is necessarily safe to use as an earth ground. Dean Kukral PS: We have discussed this topic in late 2003 and early 2004. Steve Collins wrote a definitive letter on the topic on Jan 1 2004. I will take the liberty of copying it from the PCBUILD archives and presenting it here: Date: Thu, 1 Jan 2004 From: Steve Collins Organization: AlternateRealities Computers Subject: Re: Grounding yourself; Was: Adding memory - grounding yourself Hi Dean, After spending 20 years in the semiconductor industry (including FAB and Probe & Test), I think that I can consider myself a bit of an ESD expert. I think that the confusion here is being caused by the term "grounding". In this case, the term is not really being used properly (or maybe it's more accurate to say that it is not being applied properly). Grounding is required when the potential of some part of an electronic or electrical circuit must be set at the same potential as the planet Earth. This is accomplished simply by connecting (or "grounding") that part of the circuit or component to the planet through a conductive piece of material with a resistance of less than 1 ohm. When dealing with ESD, the concern is not with the grounding of any element. The concern is with maintaining anything that will touch, or anything that will come close to each other, at the same electrostatic potential. If you are grounded through a wrist strap, and your case is sitting at a potential of 5KV due to electrostatic build-up, then grounding is actually a bad thing since you will definitely draw an arc as soon as you get close enough to the case. So, the focus here is to maintain all elements that come in contact at the same potential: Connect your wrist strap to the object that you are working on. In the case of a computer, clip the strap to a bare piece of metal that is part of the case. If you have a number of objects that you are working on (e.g. a hard drive that is to be mounted in the case, new memory, etc.), then place all objects on a conductive mat and connect your wrist strap to the mat. It is NOT necessary to ground any part of this setup. Remember that the object is simply to bring all elements to the same potential. We never recommend using any part of a live circuit (including house wiring) for any purpose other than providing power to an electrical instrument or appliance. NEVER connect a living thing to your house wiring. This includes the cat, the fish, the canary and, oh yes, YOU! If you require a ground reference, install a separate ground bus that is not part of, or near, your house wiring. NEVER remove, install or replace components on a device that is connected to a source of power (i.e. ALWAYS unplug the power supply before doing any component work). Follow these simple rules and you and your components will live to see another day. Regards, Steve Collins AlternateRealities - High Performance Computers, Clusters and Infrastructures ************************************************ ----- Original Message ----- From: "Thomas Mayer" <[log in to unmask]> Sent: Tuesday, August 15, 2006 11:50 AM Subject: Re: [PCBUILD] New here, need help BADLY! Dean ESD can vary between 200 volts and 2,000 volts. If the computer case is not grounded, there is a risk that the charge could reach some internal electronic computer components before dissipating into the atmosphere. And, once the power supply itself is turned off, there is no electricity reaching the internals, but the remaining connection to a grounded outlet provides a ground for the case. Of course working in the power supply itself is an exception. See http://www.build-your-own-cheap-computer.com/static-electricity.html Tom Mayer Dean Kukral wrote: > I disagree that to ground through the case (either by touching or by using > a > wrist strap) that you should have the power cord plugged in. > > Just the opposite. Unless you know what you are doing, you should never > have the power cord plugged in when you are working inside an electrical > device!!! > > The purpose of touching the case and/or using a wrist strap is to drain > static electricity off of yourself so as not to damage any integrated > circuits. There is absolutely no need to have the case plugged in to > serve > as a ground. Static electricity (free electrons) will tend to spread > themselves out on the case and drain themselves off quickly at the corners > and other sharp points. > > Dean Kukral > > > ----- Original Message ----- > From: "Thomas Mayer" <[log in to unmask]> > Sent: Monday, August 14, 2006 11:56 PM > Subject: Re: [PCBUILD] New here, need help BADLY! > > > You can either get a grounding wrist strap or, follow Thomas Harold's > suggestion to touch the case often as you are working. However, to > ground through the case, the power cord should be plugged in, if it is a > 3 wire grounded connection, and then turn the power switch off on the > power supply and not just the case. Of course, no matter which method > you use, it is always best way is to avoid touching any contact points. > > Tom Mayer Visit our website regularly for FAQs, articles, how-to's, tech tips and much more http://freepctech.com