ungrounded computer???

Hi Everyone:
Is it unsafe to run a pc without a grounded outlet?
and if so what would it damage?

Thanks:

 

Let me explain the purposes of a ground conductor in an electrical system and you can judge for yourself, based on your particular circumstance.

First, and most importantly, a ground is desirable so that all exposed metal housings can be held at ground potential by bonding them to this ground conductor. If it isn't present, the possibility exists that a live circuit conductor could become shorted to the cabinet and energize it. This isn't dangerous yet, but when you come in contact with any part of the housing, your body also becomes energized. That's still not a serious problem until you also touch something that IS grounded. Then you become a circuit element and may not survive the experience.

An example would be; You plug your computer in, it has a shorted line conductor that is touching the housing, you take the cable from your modem in one hand and in the process of connecting it to the computer, you touch the housing first. You will receive a not so healthy jolt.

The second reason for grounding the computer is to reduce RFI (Radio Frequency Interference) that it has a tendencency to produce.

Another reason would be to protect the circuit elements in the computer from either static or dynamic energy damage when you happen to touch them in the course of servicing the machine. A well grounded machine as well as a well grounded tech is mandatory for this reason.

Yet another reason is to comply with the N.E.C. (National Electrical Code). The N.E.C. requires grounding in all current installations and has since the early 50's. (Perhaps even before although it wasn't enforced) The N.E.C. does not however, require older systems to be brought up to that level.

If you think none of these will ever be a factor in your case then you can operate without harming the computer. It's you that we need to be concerned about.

If you must use it ungrounded, be sure to unplug the power cord from it, as well as all peripherals, before doing any cable connecting/disconnecting or any internal service. With the proper precautions , you'll be safe enough.

 

Wasn't Thinking of my own safety, just the computer system.
Thanks for the answer!!

 

If not grounded, current will follow the line of least resistance. Especially dangerous if one is in water or a wet surface. We all know about .

A two prong plug completes the electronic circuit and the computer functions properly as well as any other electronic device.
I don't believe there any PC's without the third plug?

 

ZZAAAAAAAPP

I have no vast experience wth computers. Ignoring potential for harm to persons (BAD IDEA) and any outside sources, is there danger to a computer's components that are not bonded to ground?
Hmmm. How about static electricity, real, and severe in drier climates. All the fans that are spinning are creating static, any spinning disks are creating static, there is alot of wiring and electrical devices in there, many will create EMF's.
OK, so having accepted that, most if not all the components are bonded to gether to the metal case of the computer. This case will carry and slowly dissipate all this voltage potential in relation to earth, and so all components are subjected to this bias. I am talking about "normal" conditions, with no ground faults or short circuits anywhere.
Then along comes this neutarl wire, that white wire at the recepticle on the wall, it is, or should be hovering somewhere around local earth potential, which is where the static is trying to go.
Extra effort is wisely made to keep this (oversized neutral) white wire near earth ground potential on things like computers (though you best not touch it it could kill you).
Compare that white wire to your (now disconnected from earth) computer frame, ya know the one with the variable voltage on it. Does not that alone represent potential harm to components? Doesn't all the static created by the computer need a good low resistance path to dissapate to something near the white wires potential?
Probable everyone has seen static build enough potential to jump an air gap, in that computer case some gaps are pretty small. Is every thing insulated that well in there that it can resist a high valtage?
After all that's said, laptops aren't grounded when on battery only. Maybe the makers apply extra safeguards when designing to guard from static, I don't know, I'm asking?
My computer is connected to ground and I still think it's best kept that way even if it cost something to do it.

 

My contribution and understanding of the questions posed are very limited.

As I understand it, ground within a circuit as designed are different from earth ground. But the totality of the unit is earth ground. For instance a one-shot circuit builds up capacitance, and then discharges to the designer's ground in a timely sequence when the potential difference reaches the triggering potential difference or voltage that will enable a signal for a given period of time.

I believe static electricity requires an intrusive outside enabler that makes physical contact to a component causing an improper discharge of static electrity to do any damage. Some sensitive components are sheilded from electromotive forces for proctection.

 

The inherent mutual circuit element resistance to earth ground, which granted is relatively high, is sufficiently adequate to bleed off any static electric energy that could be created by the computer fan's friction effect while spinning in the dryest of air. Although this resistance will not be measurable with ordinary service instruments, it is nevertheless quantifiable and not infinite as some may think. Infinity is a seemingly contridictory absolute and we all know that absolutes are not possible. Any two thing in the universe has some resistance between each other. The value of this resistance will vary in direct proportion to the distance of separation.

In a practical world we tend to ignore such extremes because they have no useful purpose except as in this instance, to explain the apparent disappearance of energy. We know that energy can't possibly disappear so we must accept that there must be some path for static electricity to dissipate and flow to any other body of lesser charge. So that should explain where the static electricity goes that is created by the fan. That also explains why we only get zapped after walking across a carpet in dry weather when we touch something right away. If we wait, the static energy will dissipate and we become neutral again. The same process is at work there.

Moving on to the static electricity created by your body friction when it is insulated from earth ground, we have a similar situation. It does however have a different aspect, it is sometimes produced at a rate greater than the inherent mutual resistance can bleed it off. When that occurs, the body's static electric potential can remain quite high for several seconds. Waiting long enough will allow it to dissipate. If we touch something in the meantime, it will bring that object up to our level of charge. Sometimes that occurs even before we contact something, just getting near something of lesser potential can reduce the effective resistance to a point that will allow the voltage to break down the electrostatic resistance (dielectric) of the air separating the two objects and an electric spark will occur. While this spark is present, the resistance is reduced to a very low value relative to the conditions when it isn't present. During this short period, a large amount of energy flows and has the power to cause damage to delicate components. That should give some insight as to why it's good practice to connect a good earth ground to a computer chassis and then use wrist grounding straps that are connected to this same chassis, before doing any service work that might bring your body in contact with some delicate circuit component such as a chip.

So, as you can see, the greater danger from static electric discharge is from the human body to the component and not the reverse.

As far as operating a computer ungrounded, it represents little danger other than what I outlined in my original post.

You should also be aware that the white or "neutral" conductor in a home electrical system is bonded at the main switch gear per the N.E.C. (National Electrical Code) and is not allowed to be bonded to earth anywhere downstream of this point. The main purpose of this bonding is to reduce the effects of any lightning strokes (essentially static electric discharge) so that it is effectively reduced to a level that will limit damage to the building system and inhabitants. Per the N.E.C. this neutral conductor must be the same size as the other circuit conductor which is often referred to as the "live" conductor. Actually both are live conductors but only one is "live" relative to earth due to the bonding mentioned earlier.

That get us back to the safety aspect of having a grounded computer. Since the neutral conductor is not hazardous we need only worry about the "live" wire and if we bond the computer cabinet to earth ground by running a wire back to the main switch and connecting it to the ground at that point (which is the N.E.C. approved method) we have in effect made the cabinet the same potential as the neutral. Then if a fault occurs that causes the live wire to be in contact with the cabinet, current will flow and the circuit breaker of fuse will be tripped open. This protects us from danger since without that connection the cabinet can become live and not blow the breaker of fuse. That presents a hazard that should be avoided if possible. The danger is directly proportional to the available grounds present in the immediate area. For instance, if you grasped a water pipe and then touched this energized cabinet, you would receive a painful shock. On the other hand, if you were operating in a typical computer setup and had good carpeting, you might never be aware of the cabinet being energized and think all was well.

My original point was, the hazard of connecting some periphial wire that IS grounded, such as a coax from your cable modem (which is grounded per N.E.C. by the installer at the point of connection to you house.) may be the only time you are in danger. In fact, when connected, this cable is acting as your ground in effect. If you place yourself between it and the energized cabinet, you'll get a shock. Of course if it was already connected when the ground fault occured, it would have caused the breaker to trip because the coax shield is of sufficient size to conduct enough current to do that. You body, on the other hand, isn't that good of a conductor and will allow the shock to continue until you may be electrocuted and still not trip the breaker or fuse. Try not to get in the path!

I hope this helps in the understanding of the processes involved and if it isn't the longest post you'll ever see on this board, I'll append it later.

 

ZZAAAAAAPP

I'm sure no one was suggesting that it is safe to ground your computer by means of coax. And a neutral conductor should be considered live relative to earth due to circuit resistance and possible circuit imbalance in the facilities circuits and, I don't know, maybe impedence too, I'll just throw that in and see what happens.
OK following (I think) original post. How about a vacuum cleaner (possibly an ungrounded one) a duster or a person touching the frame of the unit. Could that present enough potential to an ungrounded unit to harm it?

 

Yes, most vacuum cleaners are not suitable for cleaning computers without the risk of damage to circuit board components.

Even if the computer and vacuum cleaner are well grounded, the danger still exists because the air column moving through the rubber hose create a static potential on the end fitting and it is fairly well insulated from the ground of the vacuum. This potential could possibly discharge to some component and cause harm. Grounding either device won't guard against that.

You must use a vacuum that is approved for the purpose or use dry air from an approved device. Anything less is a gamble.

 

A long time ago when I was employed by Sperry Univac all FEs and that includes IBM employees did their PMs using a vacuum cleaner. Very common practice. Can't believe a vacuum cleaner that does not make contact to any part but the circulation of its air around a component will zap that element.

 

i hear you and have done the same thing all my life but...

This was conveniently excerpted fromhere Even though they're selling a product, I think the point is still valid since I have seen it mentioned in several manuals.

 

ZZAAAAPPP

Cleaning computer with vacuum is something that's hard to resist, I've not done it, been too scared. How about bonding vacuum nozzle to (grounded) frame with wrist strap or a couple wraps of bare wire, but. if the column of air inside plastic hose is carrying a charge that may not be enough. Some wood shops running pvc for dust removal run a bare copper wire in pipe to help dissipate charge, I don't know if there is enough surface area on wire to fixall. I think restricting the volume of air, say halfway would help, though I would restrict at the oulet end of the vacuum so velocity and tyrbulance wouldn't increase at vacuum end. (I wonder if the wife will notice) Pumping Avgas requires $pecial ho$e tested/certified for conductivity to help dissipate charge. I undeerstand charge builds up on fuel and any insulator.
OK, In prior post I was thinking about an increased risk of damage to ungrounded computer that's sitting on the floor when vacuuming the floor adjacent to it. Seems like a static discharge would be best dissipated through frame to good equipment grounding conductor. Perhaps I'm not seeing the whole picture.

Side safety note:
Many injuries from people filling gas cans while the can is on a plastic pickup bed liner or in trunk on mat, the static charge builds up enough in the can until ZZAAAPP it finds a good enough path to suddenly equalize charge. Can should be on the ground/cement. Also some explosions while fueling car, believed usually from going to get money twisting rear on nylon going back and touching nozzle while fueling.

 

I think the best way to find out if operating a computer
ungrounded will hurt the unit, Is to run a test.
I've had a computer hooked up to the same ungrounded
outlet for 5 yrs and it still runs fine.
Did quiet a bit of work on it and still no problems.
The only precaution i ever took was to Touch the computer frame before touching anything inside.
But i would be afraid to clean it with a vacuum cleaner.
I'v been zapped with static electricity with them.
It takes several hundred volts to generate a spark!!!

 

In order to clear my concience, I must give you a closing shot.

If you are forced by circumstances to operate with no ground connected to your computer, then you should install a G.F.I. (Ground Fault Interrupter) receptacle to power it from. They are inexpensive (<$10) and may be the best insurance you have ever bought. They will require you to connect their grounding wire to any nearby available ground or else install your own grounding electrode rod nearby to use. This will be safe but will not meet N.E.C. however. The N.E.C. requires that you either connect the ground wire back to the main service ground or to a water pipe. (nec 250-50 exception.) No other methods of grounding are recognized for this situation. That means if you hire a professional electrician who knows what what, you'll get it done right and it'll cost you more. What's new there?

I personally would probably do it like Roger_2646 but that would be my problem and me doing the smoking. I want everyone to get the best possible advice when human life safety is an issue and I have tried to supply that here. From there, you're on your own.

Zeph

 

When using a vacuum cleaner for preventive maintenance I am certainly not referring to the blowing feature. I suspect or at least in theory a violent turmoil of air can build up positive or negative ions that could discharge. Something like a miniature lightning storm. But if that condition exists it is irrelevant to a grounded vacuum cleaner question, if as stated by poster the discharge cannot be properly grounded due to a buffer condition of the blowing air and that is the problem with an ungrounded vacuum cleaner. Blowing dust or debris can cause problems. No disagreement there!! Never has been any question to that situation.