No equipment ground
- Thread starter domnic
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Speedskater
Senior Member
- Location
- Cleveland, Ohio
- Occupation
- retired broadcast, audio and industrial R&D engineering
Does the computer have a two wire or three wire cord?
three
drcampbell
Senior Member
- Location
- The Motor City, Michigan USA
- Occupation
- Registered Professional Engineer
With or without a power adapter?
A desktop machine, without a power adapter, probably has some surge suppression and static dissipation built in. It won't exactly be harmed by the lack of ground prong, but the protective circuits may be ineffective.
Laptop confusers, with a power adapter, usually run on 19v DC and are "completely" isolated from the AC mains. But if the power adapter has a three-conductor plug, it probably also contains protective circuitry.
A desktop machine, without a power adapter, probably has some surge suppression and static dissipation built in. It won't exactly be harmed by the lack of ground prong, but the protective circuits may be ineffective.
Laptop confusers, with a power adapter, usually run on 19v DC and are "completely" isolated from the AC mains. But if the power adapter has a three-conductor plug, it probably also contains protective circuitry.
- Location
- Illinois
- Occupation
- retired electrician
250.114(3)(b) does not permit you to plug information technology equipment into a receptacle that does not have an equipment grounding conductor. It is my opinion that a computer is information technology equipment.
ptonsparky
Tom
- Occupation
- EC - retired
You, as an EC, should not plug it in because you know better.
Next question: How many are are using a two wire adaptor or are plugged into a three wire ungrounded receptacle?
Next question: How many are are using a two wire adaptor or are plugged into a three wire ungrounded receptacle?
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
I've always recommended a new circuit for electronic loads like A/V systems, computer stations, etc.
You have a well-grounded, low-impedance power source, and relieve the old wiring of the burden.
You have a well-grounded, low-impedance power source, and relieve the old wiring of the burden.
ptonsparky
Tom
- Occupation
- EC - retired
Most people that have spent the money on a desktop that needs a grounded outlet, will spend the money if they have called you in
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
It's possible. The manufacturer chose a design that relies on the grounding to be intact.
ptonsparky
Tom
- Occupation
- EC - retired
Well, I don’t know about a computer since most devices now have SS logic in them most electronics are hybrid computers,, but I know what harmed a renters new 50” flatscreen....the receptacle was wired reverse polarity, three prong without ground wire not even bootleg , wire color was correct but was reversed somewhere in the circuit, when the cable tv tech came to hook up cable for said new TV ,,,, he ran an inter system bond to meter base...
Any guesses? Yup dead short thru TV because the grounded conductor wasn’t and the coax was... owner paid for that that one and he was NOT happy...so hire professionals to do your wiring is the takeaway here or at least someone who knows something lol.
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Any guesses? Yup dead short thru TV because the grounded conductor wasn’t and the coax was... owner paid for that that one and he was NOT happy...so hire professionals to do your wiring is the takeaway here or at least someone who knows something lol.
Sent from my iPhone using Tapatalk
AC\DC
Senior Member
- Location
- Florence,Oregon,Lane
- Occupation
- EC
my mac mini is two prong would that be an issue?
hbiss
EC, Westchester, New York NEC: 2014
- Location
- Hawthorne, New York NEC: 2014
- Occupation
- EC
If the plug has a ground pin it's there for a reason.
EVERY ONE OS FAR HAS SIDESTEPPED THE QUESTION.
Easy now. What was the question? "Does anyone know of any reason that a two prong outlet [ no equiptment ground ] used to power computer would harm the computer in any way?" That's impossible to say without knowing how the ground is handled. It may be just for safety or it could be actually there to do something like limit surges via internal SPDs.
Like I said above, if there is a ground prong on any electrical equipment make sure it connects to ground because you don't want to find out what happens the hard way.
-Hal
EVERY ONE OS FAR HAS SIDESTEPPED THE QUESTION.
Easy now. What was the question? "Does anyone know of any reason that a two prong outlet [ no equiptment ground ] used to power computer would harm the computer in any way?" That's impossible to say without knowing how the ground is handled. It may be just for safety or it could be actually there to do something like limit surges via internal SPDs.
Like I said above, if there is a ground prong on any electrical equipment make sure it connects to ground because you don't want to find out what happens the hard way.
-Hal
- Location
- Illinois
- Occupation
- retired electrician
That might fall into the provisions of the Exception to the parent text in 250.114.
Frank DuVal
Senior Member
- Occupation
- Electrical Contractor, Electrical Engineer
And just how does that happen for the thousands of laptops with two wire cords? Of course, the same way it happens with computers with three wire cords, by shunting any static electricity at the source! Ground, as in earth connection, has NOTHING to do with it.
The third wire (ground pin) is solely for personal safety. I've seen lightning damaged computers that were properly plugged into grounded receptacles with and without surge protectors.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
I just wrote a long post on this for someone else and was trying to remember who and where, so I could copy and paste, but I give up.
All modern electronics now use what are called Switch Mode Power Supplies (SMPS) because they are smaller / cheaper / much more energy efficient than older linear power supply technology. The only down side of SMPS technology is that in the way they work, they create what's called "common mode noise", electrical noise / current referenced to ground that is always seeking to return to its source, the SMPS. Because of this, they NEED the ground reference as a return path to the power supply, otherwise that CM noise ends up circulating around inside of the equipment adding thermal and voltage stress to the electronic components and shortening their useful life. For really small SMPS, like what you have in a cell phone charger, they can make it double insulated and hardened against CM noise relatively cheaply, so that's why you see those units with 2 prong plugs. But as the power requirements go up, so does the cost to do that, so most mfrs just use a grounded plug connection to allow that return path of the CM noise to its source. That means then that the electronics MUST have a grounded connection, not just because of safety concerns, but for the long term integrity of the devices.
You can get around the shock safety issue of an ungrounded receptacle by adding a GFCI to it (406.4(D)(2) ), but the risk to your electronics is not helped by that. That is what is behind the addition of 250.114(3)(b) to the NEC, I think in the 2002(?) code and the addition (also in 2002) of 250.130(C) to allow for adding an equipment grounding conductor to an older in place circuit.
All modern electronics now use what are called Switch Mode Power Supplies (SMPS) because they are smaller / cheaper / much more energy efficient than older linear power supply technology. The only down side of SMPS technology is that in the way they work, they create what's called "common mode noise", electrical noise / current referenced to ground that is always seeking to return to its source, the SMPS. Because of this, they NEED the ground reference as a return path to the power supply, otherwise that CM noise ends up circulating around inside of the equipment adding thermal and voltage stress to the electronic components and shortening their useful life. For really small SMPS, like what you have in a cell phone charger, they can make it double insulated and hardened against CM noise relatively cheaply, so that's why you see those units with 2 prong plugs. But as the power requirements go up, so does the cost to do that, so most mfrs just use a grounded plug connection to allow that return path of the CM noise to its source. That means then that the electronics MUST have a grounded connection, not just because of safety concerns, but for the long term integrity of the devices.
You can get around the shock safety issue of an ungrounded receptacle by adding a GFCI to it (406.4(D)(2) ), but the risk to your electronics is not helped by that. That is what is behind the addition of 250.114(3)(b) to the NEC, I think in the 2002(?) code and the addition (also in 2002) of 250.130(C) to allow for adding an equipment grounding conductor to an older in place circuit.
Frank DuVal
Senior Member
- Occupation
- Electrical Contractor, Electrical Engineer
I was following along until you said the common mode noise is seeking to return to the source (the SMPS), and this makes thermal and voltage stress inside the equipment. But the SMPS IS inside the equipment, so what does the external ground have to do with it?
Now if you are saying the common mode noise goes back to the power company, then I see it having to return to the SMPS via hot, neutral, gnd, whatever, but then how does that cause thermal and voltage stress inside the equipment?
Now if you are saying the common mode noise goes back to the power company, then I see it having to return to the SMPS via hot, neutral, gnd, whatever, but then how does that cause thermal and voltage stress inside the equipment?
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