Should the PSU be physically grounded to the case via ground wire?

By BillAllen55
Feb 4, 2009
  1. I am currently in the process of putting together components for a new computer build.
    (as Mr Cranky well knows) :wave:
    I was talking with a 'gamer' at work about the components which I will be putting together over the weekend. (I'm NOT a gamer) He advised that with all of his gaming computers' he 'grounds' the PSU to the case with a ground wire connected from the PSU to a non discript area under the MB.
    This a list of the MB and CPU I will be installing:
    GIGABYTE GA-EP45-DS4P LGA 775 Intel P45 ATX Intel Motherboard
    Intel Core 2 Duo E8500 Wolfdale 3.16GHz 6MB L2 Cache LGA 775 65W Dual-Core Processor
    My question is: with this arrangement, is it necessary to have a physical ground 'wire' going from the PSU to an area underneath the MB?
    Obviously the PSU must be grounded obviously all circuits must be organized in a manner that properly uses the positive and ground config. I'm asking specifically if the PSU needs a wire ground connected to it leading to the computer case?

  2. gguerra

    gguerra TS Maniac Posts: 317

    The PSU is screwed into the case using metal screws. The metal box that houses the PSU is in contact with the case (usually metal). The electrical connection is always a 3-prong (grounded) connection. So no,you dont need to run a separate cable for ground.
  3. kimsland

    kimsland Ex-TechSpotter Posts: 14,524

    @gguerra There are no "Stupid" questions, only "stupid" answers

    I hope this is not the normal way you post :suspiciou
    You may have been a tad harsh in your answer don't you feel?
    It would be difficult to receive a "Thank-you" from being helped with your post
  4. gguerra

    gguerra TS Maniac Posts: 317

    I didn't mean anything by it. Would it have been better if I said the "dumbest" thing I ever heard? because that is basically what I meant. Common sense would tell you you don't need a ground wire and I've never heard of it. Been building PC's over 20 years now. BTW I've only received a "thank you" like one time so that is not what I seek. I do like to help however, so I am sorry if I seemed harsh.
  5. jobeard

    jobeard TS Ambassador Posts: 9,156   +598

    remove this and it would have been a great answer :)
  6. IndyRacer

    IndyRacer TS Rookie

    Wow, thats was harsh.

    I am new here and I was just reading things around the website,
    and bumped into this. and my mouth dropped.

    and I had to reply.
    When someone ask a question, its because they don't know the answer, or are not sure of the aspects of what they are wondering about or trying to achieve.
    and your answer just went beyond rudeness and very unhelpful at all.

    And @BillAllen55

    To answer or help in what your trying to gain knowledge about.

    Some power supplies do (self ground) themselves when you screw on the PSU to the frame of the case.
    But some older models do not.
    I have seen a few cases that even hi experienced technicians have grounded them for reassureance in some cases.
    but it all very well depends on the situation and the kind of PSU you are using.

    It is best to read the manual of your PSU you are trying to find answers for to gain better aspects of your answer.

    But I do know that many of the manuals do not describe this im sure.
    So I would guess its the reason why you asked here, in hopes to get and final correct answer.

    But most PSU's do not need any grounding at all,
    as they are constructed with some sort of self grounding mechanics already built in.
    and some even have far greater features within,
    such as self trip and fuses to protect the Power Supply as well as the components
    of the case, MOBO, CPU, Memory Chips and the PSU itself.

    I believe that you are just fine, and do not have to worry about grounding issues.

    Also, the PSU comes with a 3 prong plug to plug into the wall,
    that 3rd prong is a grounder.
    it grounds from the wall socket.

    so that helps in grounding the PSU aswell.

    I hope I help you far better than your previous attempted of help.

    Be safe :D

  7. gguerra

    gguerra TS Maniac Posts: 317

    I have removed the "offensive" comment in my post.. All should be good now Indy. Enough said on this topic (from me anyways)
  8. captaincranky

    captaincranky TechSpot Addict Posts: 11,462   +1,760

    I am having a hard time getting my head around the concept that older PSU cases might not be physically grounded. This actually seems like it might be illegal, and in any event it also seems doubtful that UL labs would approve such an arrangement, at least certainly not in the era of polarized plugs on AC equipment.
    I understand that small "wall wart" type PSUs don't have grounded cases,, but a plastic case falls into the realm of "double insulated" equipment.

    That said, to the best of my knowledge, Mr Allen is building an entirely new system, so it's really doubtful that we're going to be dredging up a PSU from the year one to power this jewel.

    Fun facts: Every BLACK wire coming out of the PSU is an internal ground, they should all be common to one another.

    A standard three wire cord/plug has TWO grounds already, (the common is actually a ground),. that's a believe it or not.

    A really fast way to check for ground integrity is to do this; procure a simple AC circuit tester, you know,one of the little neon glow jobbies. Then, with a three wire extension cord, insert one wire of the circuit tester into the "HOT" wire of the extension cord, (This is the shortest straight terminal blade), and touch the metal of the PSU with the other wire of the circuit tester. If it lights, it's grounded, period.

    A standard three wire plug's terminals are as follows;

    Ground: The round terminal, connects to green wire
    Common: The longest blade type terminal, connects to a white wire.
    "Hot" or Positive: The shortest blade type terminal,. connects to a black wire.

    Very important please take note.
    In the field of electrical equipment BLACK wires are ground!

    In the field of electrical wiring (such as house wiring) BLACK wires are always HOT!
    Be aware of this, for safety's sake

    In days of old, warrior/poet was truly a noble profession indeed. So you can imagine my profound dismay when I finally realized that they have been supplanted by, "imbecile/experts". If you really want to encourage this persons OCD, then what needs to be done is to connect the computer case to 4 gauge copper wire, which you would then run to an eight foot copper stake driven in to the earth under the house. Only then would proper grounding be assured!!:rolleyes::haha:
  9. kimsland

    kimsland Ex-TechSpotter Posts: 14,524

    This coloring is not universal
    And negative (ie Positive; Negative\Neutral; Earth) is not ground exactly

    Black is not Active positive in every country (ie Red is usually positive elsewhere)
    I've always been concerned when support say "test your power, the color will be... "
    I don't believe this is the safest approach for the layman or want-a-be electrical tester

    As a trade qualified electrician, I have seen the pictures of users who have "tested" their electrical wiring (I think they show all apprentices this to shock them) And they weren't pretty

    Oh and I have also seen the ground wire on older power supplies, that screw into the chassis (now being non-existent)
  10. captaincranky

    captaincranky TechSpot Addict Posts: 11,462   +1,760

    That's great kimsland. Bill is from Oregon, is it different there!

    Well, is your best guess that we're dealing with an "older" PSU here?

    The case is the "chassis" , and we're building a computer in 2009, not 1969.
  11. kimsland

    kimsland Ex-TechSpotter Posts: 14,524


    Bill ? Don't know him ;) (William maybe :confused: )
  12. captaincranky

    captaincranky TechSpot Addict Posts: 11,462   +1,760

    Sorry for the double post, truly
  13. mailpup

    mailpup TS Special Forces Posts: 6,964   +355

    For what it's worth, I have a Mushkin 650W power supply that comes with a ground wire that must be secured to the case chassis. See one here I think it only came out about three years ago. It's the only one I've ever seen with a separate ground wire although I can't say I've seen vast numbers of them.

    So unless the power supply has a dedicated ground wire to attach to the chassis, I wouldn't worry about doing anything special to ground it.
  14. captaincranky

    captaincranky TechSpot Addict Posts: 11,462   +1,760

    Wow, I stand in awe. God, I hope that Mr. Allen didn't buy this exact supply, otherwise this whole thread is for naught.

    I would actually want to check that particular unit to find out if the case is grounded. It almost seems like a selling point, or something precipitated by the PSU's modular wiring. You know, if you don't use all the wires, you don't have all the grounds.

    I still think that a pair of battery jumper cables to the cold water supply of the toilet would be the most certain method of assuring a positive ground.

    I still think it's illegal to have a piece of equipment in a metal case, wherein the metal case is not grounded. If the case isn't grounded, and you are, then any kind of ground loop or short circuit could result in your death. I don't think that that's on anybodies marketing agenda, although I might be naive.

    The only qualifier here is that in high current applications, it might be advantageous to have a large size grounding wire to prevent voltage drop and/or fluctuations due to insufficient capacity of the returns, (grounds). And you made me miss jeopardy, thanks a bunch.
  15. Tedster

    Tedster Techspot old timer..... Posts: 6,000   +15

    it's always a good idea to ground when you can. remember the output of the PSU is DC not AC, so be careful not to short out. The AC part can be grounded if there is a ground lead, however, the 3rd wire should automatically be grounded to your outlet via the power cable.
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