CSE Pure Power - Summer 2008 - (Page 22) ❯❯ PURE POWER // SUMMER 2008 22 grounding story Using the 750 ohms from above in properly graded gravel as a starting point, with one ground rod and adding 23 more results in the following: (750/24) x 2.16 = 67.5 ohms. Working from the desired results of 25 ohms = (277/24 x 2.16). Best application of using 24 ground rods would probably be in a ground ring around the building. Table 3 – Effect of temperature on soil resistivity TEMPERATURE (C) -5 0 0 10 20 30 40 50 © IEEE Table 4 – Multiplying factors for multiple rods NUMBER OF RODS 2 3 4 8 12 16 20 24 © IEEE RESISTIVITY (OHMS-CM) 70,000 30,000 10,000 8,000 7,000 6,000 5,000 4,000 FACTOR 1.16 1.29 1.36 1.68 1.80 1.92 2.00 2.16 CONCLUSION With the growth of high-tech facilities with sensitive electronics, one will see the 5-ohm resistance value as the new target for grounding system. The engineer will need the soil resistivity numbers for the facility. More complex or enhanced grounding systems will be designed. Contractors will have more challenges and may be required to include test equipment in his or her arsenal of tools. In- spectors will inspect many of the grounding components as they are installed. Owners will benefit by having a good grounding system ABOUT THE AUTHOR because their computers will work better, health care equipment will work better, and telecommunication systems will work better. Ostendorf is Senior Electrical Engineer, Senior Associate, ME Group, Omaha. It’s the that matters most! Visit us at csemag.com for the latest engineering news and information on electrical, fire, HVAC, and plumbing systems. NEW Technology NEW on our site: • BLOGS • INDUSTRY SEARCH • WEBCASTS The first destination for consulting engineers www.csemag.com www.purepowermagazine.com http://csemag.com http://www.csemag.com http://www.csemag.com http://www.purepowermagazine.com
Table of Contents Feed for the Digital Edition of CSE Pure Power - Summer 2008 CSE Pure Power - Summer 2008 Contents In the News Industry Roundup Risk Assessments for COPS Grounding Requires More Power Systems to Protect Healthcare Important Changes Coming in NFPA 70E A Look at Arc-Resistant Switchgear Agencies and Associations New Products Ad Index CSE Pure Power - Summer 2008 CSE Pure Power - Summer 2008 - CSE Pure Power - Summer 2008 (Page Cover1) CSE Pure Power - Summer 2008 - CSE Pure Power - Summer 2008 (Page Cover2) CSE Pure Power - Summer 2008 - Contents (Page 1) CSE Pure Power - Summer 2008 - Contents (Page 2) CSE Pure Power - Summer 2008 - Contents (Page 3) CSE Pure Power - Summer 2008 - In the News (Page 4) CSE Pure Power - Summer 2008 - In the News (Page 5) CSE Pure Power - Summer 2008 - Industry Roundup (Page 6) CSE Pure Power - Summer 2008 - Industry Roundup (Page 7) CSE Pure Power - Summer 2008 - Risk Assessments for COPS (Page 8) CSE Pure Power - Summer 2008 - Risk Assessments for COPS (Page 9) CSE Pure Power - Summer 2008 - Risk Assessments for COPS (Page 10) CSE Pure Power - Summer 2008 - Risk Assessments for COPS (Page 11) CSE Pure Power - Summer 2008 - Risk Assessments for COPS (Page 12) CSE Pure Power - Summer 2008 - Risk Assessments for COPS (Page 13) CSE Pure Power - Summer 2008 - Risk Assessments for COPS (Page 14) CSE Pure Power - Summer 2008 - Risk Assessments for COPS (Page 15) CSE Pure Power - Summer 2008 - Risk Assessments for COPS (Page 16) CSE Pure Power - Summer 2008 - Risk Assessments for COPS (Page 17) CSE Pure Power - Summer 2008 - Risk Assessments for COPS (Page 18) CSE Pure Power - Summer 2008 - Grounding Requires More (Page 19) CSE Pure Power - Summer 2008 - Grounding Requires More (Page 20) CSE Pure Power - Summer 2008 - Grounding Requires More (Page 21) CSE Pure Power - Summer 2008 - Grounding Requires More (Page 22) CSE Pure Power - Summer 2008 - Grounding Requires More (Page 23) CSE Pure Power - Summer 2008 - Power Systems to Protect Healthcare (Page 24) CSE Pure Power - Summer 2008 - Power Systems to Protect Healthcare (Page 25) CSE Pure Power - Summer 2008 - Power Systems to Protect Healthcare (Page 26) CSE Pure Power - Summer 2008 - Power Systems to Protect Healthcare (Page 27) CSE Pure Power - Summer 2008 - Power Systems to Protect Healthcare (Page 28) CSE Pure Power - Summer 2008 - Power Systems to Protect Healthcare (Page 29) CSE Pure Power - Summer 2008 - Important Changes Coming in NFPA 70E (Page 30) CSE Pure Power - Summer 2008 - Important Changes Coming in NFPA 70E (Page 31) CSE Pure Power - Summer 2008 - Important Changes Coming in NFPA 70E (Page 32) CSE Pure Power - Summer 2008 - Important Changes Coming in NFPA 70E (Page 33) CSE Pure Power - Summer 2008 - Important Changes Coming in NFPA 70E (Page 34) CSE Pure Power - Summer 2008 - A Look at Arc-Resistant Switchgear (Page 35) CSE Pure Power - Summer 2008 - A Look at Arc-Resistant Switchgear (Page 36) CSE Pure Power - Summer 2008 - A Look at Arc-Resistant Switchgear (Page 37) CSE Pure Power - Summer 2008 - A Look at Arc-Resistant Switchgear (Page 38) CSE Pure Power - Summer 2008 - Agencies and Associations (Page 39) CSE Pure Power - Summer 2008 - Agencies and Associations (Page 40) CSE Pure Power - Summer 2008 - New Products (Page 41) CSE Pure Power - Summer 2008 - New Products (Page 42) CSE Pure Power - Summer 2008 - New Products (Page 43) CSE Pure Power - Summer 2008 - Ad Index (Page 44) CSE Pure Power - Summer 2008 - Ad Index (Page Cover3) CSE Pure Power - Summer 2008 - Ad Index (Page Cover4)
For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.