How To Test Your Data Center’s Grounding System Nashville, Tennessee March, 2010 John Howard [email protected] Where Grounding Bonds With Science® Agenda –– Common Common Ground Ground // Importance Importance –– Pyramid Pyramid ?? –– Site Site Specific Specific Design Design –– Achieving Achieving55 Ohms Ohms –– Electrode Electrode Choices Choices –– Pros Pros//Cons Cons –– Ground Ground System System Testing Testing –– Why Why95% 95%Invalid Invalid Why Ground? – Equipment Protection – Satisfy Warranty Requirements – Service Protection – System Performance – Personnel Safety (NEC) Typical Performance Reqs – National Electric Code (NEC)< 25 OHMS “Practical Safeguarding of…..” – IEEE Standard 142 Equipment Dependent – IEEE Standard 1100 < 5 OHMS – Motorola Standard R-56 < 10 OHMS – Verizon / Typical Wireless < 5 OHMS – Typical DataCenter / Switch < 2 OHMS Electrical Protection Systems Protection PyramidTM RF RF AC AC Surge Surge Telco Telco // Data Data Lightning Lightning Grounding Grounding Surge Dissipater Surge Collectors 4 Step Engineering Ground Design Process Ground System Resistance? – The Simple Formula: R=P/A R = Ground System Resistance P = Soil Resistivity A = Cross Sectional Area of The Ground System Four Step Engineering Process – Purpose of Design? – Predictable Ground System Performance – Four Steps – (1) Data Collection / Testing – (2) Design – (3) Installation – (4) Inspection / Testing Data Collection / Testing (Step 1) – Info Required – Soil Resistivity – Performance Requirement – GeoTec Report (If Available) – Site Diagram – Area Available, Structures? Soil Resistivity Testing t n r re u C w o l F R=E/I 4-Pole Digital Ground Tester Voltage Drop Internal Design Process (Step 2) – Develop Soil Model – Evaluate Soil Data – Enter Soil Data – Computer Model Of Site – Develop System Design – Buried Ground Ring Size – Electrode Lengths – Electrode Quantity Ground System Resistance……, Defined Ground System Resistance? Resistance between the Ground System and Remote Earth Testing Methods – Two Test Methods – Fall Of Potential Test - Inserting Current / Measuring Voltage – Clamp-On Test - Inducing Voltage / Measuring Current Fall Of Potential Test Fall Of Potential Test Current Flow 3 Pole Meter R=E/I Voltage Drop Neutral Remote Current Electrode Earth Fall of Potential 175 165 155 145 135 125 115 105 95 85 75 65 55 Resistance Ground Resistance (Plateau) Voltage Probe Spacing (%) 0 10 20 30 40 50 60 70 80 Figure 2. Ground System Test Results 90 100 Ground Resistance Testing Neutral Connected You are testing every ground in parallel. Current Clamp-On Test Meter – Advantages – Quick and Easy – No Disconnecting Neutral – No Long Leads, Property – Disadvantage – Ground Configuration – Finding Proper Location To Test – Invalid 95+% Of The Time Clamp -On Meter Operation Utility Neutral Line NeutralGround Bond Grounding Conductor Series Loop Parallel Loop Current Flow R = ??? E/I Clamp -On Meter Operation Current Path Reading: <1 Ohms? Invalid Reading Testing Solution? – Summary / Cure – Design To Test - Single Point Ground? Neutral Access? Alternative Ground? GRM2000RS? – Use Experienced Professionals - Ground System Testing Is Difficult, most of the time. 1-800-962-2610 Phone 1-310-214-4000 Fax 1-310-214-1114 www.Lyncole.com [email protected] Where Grounding Bonds With Science®