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July 8 webinar titled "Grounding systems: Safety and noise issues"

Last post 07-10-2008 10:13 AM by asnell. 6 replies.
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  • 07-10-2008 9:43 AM

    July 8 webinar titled "Grounding systems: Safety and noise issues"

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    If you missed our July webinar about grounding issues, you can catch it on-demand on our Web site free-of-charge:

    https://event.on24.com/eventRegistration/EventLobbyServlet?target=registration.jsp&eventid=99741&sessionid=1&key=2365FC51DB2EAFC375DBF6CE8FC5B7A4&sourcepage=register

    Due to time constraints, our presenter Richard Reagan was not able to answer all of the attendee questions during the Q&A session. However, he has answered those questions below. If you have more questions, you can post them here in the forum or email Richard at rodeo59@yahoo.com.

     

     

  • 07-10-2008 9:48 AM In reply to

    Re: July 8 webinar titled "Grounding systems: Safety and noise issues"

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    Q: I have heard that our sattellite dishes need to be grounded with a halo gound. The person reccomends four 8ft rods in a ring which is about 25 ohms, and is opposed to us going deeper. I want to put them down to 40ft which gives us less than 5 ohms. What would you advise? 

     

    A:  I would get as good a ground as you're financially/practically able to do. Lower number is better. You may only be able to get 5ohms, but that is way better than 25ohms. Remember all this has to be bonded together w/studio ground or you may have to opto isolate your feed as you may produce an imbalance between your old ground and the better newer ground.   A halo ground is a loop (copper strap or that wire braid that looks like a kelum) that is made around a building. Usually this is grounded to earth at the four corners via copper rod. Some have it driven in at 45 degree angle to direct energy away from the building. All connections are cadweld; all bends are radius, not 90 degree.  

     

    Check out:http://www.copper.org/applications/electrical/pq/casestudy/florida911.html  Power & Systems Innovations www.psihq.com

     

  • 07-10-2008 10:01 AM In reply to

    Re: July 8 webinar titled "Grounding systems: Safety and noise issues"

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    Q: What is the best method for grounding an AM station that is built on dry sand? We are in the desert in SE California. Flooding periodically could be one of the options. Are there any other recommended methods? If you aren't versed on this, could you steer me to some resources that can help?  

     

    A:  All of the AM facilities that I am familiar with are built on bottom land near good ground water table. I don't know how deep a good ground would be where you are but with the tools I described, you should be able to tell what you have now. Of course, in AM, ground is everything.

     There is a company Graham Brock Associates that may offer more info to your situation. http://www.grahambrock.com/am_ground.htm

     

  • 07-10-2008 10:04 AM In reply to

    Re: July 8 webinar titled "Grounding systems: Safety and noise issues"

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    Q: Any difference between "lightning protection grade" flat copper strap that is supposed to be something like 99 percent pure copper, and the so called copper roof flashing sold at home improvement stores that is supposed to be about 97 percent pure copper? It all looks (and acts) the same to me.

     

     

    A:  Copper is copper, but the expensive one is UL listed, which means a sample was tested, and for insurance, it might make a difference in paying a claim. Ask your insurer. Your results may vary. It is always best to have a trail of accountability, in case of liability, that way you can say I just did what I was told.

     

  • 07-10-2008 10:10 AM In reply to

    Re: July 8 webinar titled "Grounding systems: Safety and noise issues"

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    Q: In relation to audio/video noise. Is there a standard for voltage differentials between two neutral and or ground busses in a facility?  

     

     

     

    A: I would say no. If everything is properly bonded together, the difference should be near zero. Remember the AC power neutral should only be attached to the system ground at the panel or at an isolation transformer. This ground is bonded to the building steel and halo ground if there is one. One of the present problems is resistance due from wire distance between panel and equipment. One of the possible cures is to have a ground system with the shortest path to (ground) building steel or outside halo ground with everything tied/bonded together. At any point in your ground you will measure a low impedence path. This may be expensive to achieve but will be the solution to different potentials in plant. If the distance is really great, you can set an isolating transformer at your equipment site, make up a new power panel neutral and ground at this point.

     

  • 07-10-2008 10:12 AM In reply to

    Re: July 8 webinar titled "Grounding systems: Safety and noise issues"

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    Q. In a small telecommunications facility, is it necessary to have to different ground, one for protection and other for signals? If so, where must be connected each one? And are both connected together? 

     

    A. No. This would be dangerous and illegal.Everything must be bonded together. NEC 250-66single point at service for a small facility, past service the ground and neutral are separate.

     

  • 07-10-2008 10:13 AM In reply to

    Re: July 8 webinar titled "Grounding systems: Safety and noise issues"

    Reply Contact
    Q. If a facility is big size building, is it recommended to have multiple grounds?  A. You will probably have many, many grounds in a big building (usually all around the parameter, and the floor, and the building steel). The trick is to make certain that they're all bonded together. NEC 250-66

     
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