An Electrical Question....

Discussion in 'Archived Threads 2001-2004' started by Brian Vaughan, Jan 26, 2002.

  1. Brian Vaughan

    Brian Vaughan Stunt Coordinator

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    I just tried to install a PS Audio electrical outlet in place of my current one, but I ran into a problem. Despite the fact that my current outlet is three pronged, I discovered that there is no ground wire! My apartment building was built in the 1920s so this doesn't surprise me too much. The instructions from PS Audio said not to install in an ungrounded outlet so I put back my old one. My question is, can I ground the outlet by running a copper wire from the ground screw to the metal junction box, or am I going to have to get an electrician in to run a new line?

    Thanks, Brian
     
  2. dougW

    dougW Stunt Coordinator

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    Brian, were I you, I believe I would hire a pro. Electricity as a hobby is dangerous. Let him insure the new wire is grounded properly. The actual cost of hiring someone is probably fairly low, like 75-100 bucks.

    Goodluck!

    Lex
     
  3. Gary Silverman

    Gary Silverman Stunt Coordinator

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    Brian, You may have a ground. If the wiring is BX cable, the metal jacket of the cable is the ground path. If it's conduit, the conduit is your ground path. You may have one of these systems and not have a ground, though. To check it, use a meter or test light and test from the hot(black or colored wire) to the box. If you get 120v, you have a ground and can use the electrical box as your ground.
     
  4. Brian Vaughan

    Brian Vaughan Stunt Coordinator

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    Thanks guys. I just went out and picked up a voltage meter from radio shack and checked the outlet. I got 120v by connecting to the short (hot) slot and the round third prong. DOes this mean that the outlet is grounded despite no ground wire being hooked up? I'll check the grounding of the junction box as soon as I remove the outlet again (don't feel like doing it whilst the games are on!).

    Thanks, Brian
     
  5. Allan Jayne

    Allan Jayne Cinematographer

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    If the outlet does not have a specific ground, even though you get a 120 volt reading from the hot wire to the junction box, even though the system uses BX cable or conduit, you do not have a reliable ground. A correctly grounded system using BX cable or conduit also has a bare (or green insulated) wire inside that is the ground conductor.
    If you do not have a reliable ground things may work OK at least for the time being, but you are still subject to ground loop hum or video herringbone problems etc.
    Video hints:
    http://members.aol.com/ajaynejr/video.htm
     
  6. Wayne A. Pflughaupt

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  7. Brian Vaughan

    Brian Vaughan Stunt Coordinator

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    Thanks for all the help and advice. I think I am going to stick with my original configuration for a little while then decide whether to install the new outlet. I'll probably end up calling in an electrician to at least confirm that it is safe to install the new outlet and that the circuit is grounded. I'd rather spend some money on that rather than risk any electrical hazards.

    Thanks, Brian
     
  8. Mark Fitzsimmons

    Mark Fitzsimmons Supporting Actor

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    I just bought a Monster Cable Power Center HT700. All of my wall outlets are two pronged. Will a ground be necessary? If so, how will I do it?
     
  9. Brian Vaughan

    Brian Vaughan Stunt Coordinator

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    Wayne, I just realized that my Monster Power 3500 has a green light on the front panel which lights up when the system is properly grounded. Luckily mine is lit! So I suppose the outlet is grounded. Now I'll just have to see if the PS Audio outlet gives the same result.

    Thanks again, Brian
     
  10. Gary Silverman

    Gary Silverman Stunt Coordinator

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    Wayne got it right except that the code allowing the metal jacket or conduit as a ground path is the minimum standard. A lot or electricians will use bx with a ground or a ground wire in the conduit anyway, thus giving a good ground path even if the jacket or conduit integrity is compromised(i.e. loose locknut or setscrew). I do that with all my cicuits without regard to them being isolated ground or not.
     
  11. Gary Silverman

    Gary Silverman Stunt Coordinator

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    One more thing. You can still get a ground reading through the grounding hole in the receptacle and not have a good ground. The screws that hold the receptacle to the box will ground it, but unless the yoke is tight to the box, it may not be a good ground. There are self-grounding receptacles available and/or use the ground within a romex cable, or add a grounding pigtail from the box, for bx and conduit.
     
  12. Brian Vaughan

    Brian Vaughan Stunt Coordinator

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    Thanks for the information Gary. Now that I have thought it over, I think I am going to have an electrician come over before I do anything to the outlet, just to be safe. I'm sure any improved fidelity from the new outlet would not be worth a possible electrical accident or violation of safety code.

    CHeers, Brian
     

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