Up Time Magazine- February/March 2008

motor testing upload The Right Connections Creating Bonds That Last by Howard W. Penrose, PhD, CMRP & Richard Borge A s an industry we have drifted away from proper electric motor connection techniques. This becomes quite evident as the number of issues related to taped connections has been increasing. In fact, the number of instances we have directly been involved with even since the article published in December has been disturbing. While confirming the materials we were to include in this article, we discovered that information on making connections, or splicing the leads, is neither readily available nor updated with any new changes. We will use the terms ‘splice’ and ‘connection’ interchangeably throughout this article. We are going to explore the proper techniques for making electric motor connections in AC motors under 600 Volts. First, we are going to discuss the NFPA 79-2007 and the NFPA 70-2007, or National Electrical Code, rules for splicing. Second, we will discuss splicing kits followed by the appropriate method of insulating connections, if kits are not available. As far as the preparation requirements for motor connections, the connection box, lead and cable length, and openings are considered in the NEC Article 430.12 and 430.13. For the purpose of this article, we are going to focus on splice connections and not fixed terminals within connection boxes. In order to properly meet the NEC, the motor connection box must be complete and is normally metallic with the exception of instances where grounding connections are made directly to the motor housing. The connection box must protect the conductors and splice insulation from direct exposure to moisture and other contaminants. Additionally, the volume of the connection box must meet minimum requirements for standard purpose machines (See Figures 1 and 2). The lead wire from the motor and incoming power supply should be at least 6 inches in length and properly marked. This allows proper access to make and position connections within the motor housing. According to the NFPA 79, Articles 12.2.1 and 12.2.2, feeder conductors to the motor must be stranded softannealed copper. NFPA 79-2007 and NFPA 70-2007 Over the past few years we have received a number of questions related to wire nut connections for electric motors. One of the statements made within the NFPA 79, Section 13.5.9.2 is quite interesting: “Electrical connections at motor terminal boxes shall be made with an identified method of connection. Twist-on wire connections shall not be used for this purpose.” However, we have found a number of instances where instructions are provided for the use of wire nuts for electric motor connections, as well as a very large number of cases where small electric motors use wire nuts for making connections. Section 13 also discusses that the insulation material cannot be combustible and that soldered or insulation piercing connectors cannot be used. The NEC does call for the minimum insulation requirements as: “conductors must be spliced or joined with splicing devices identified for the purpose and the splices must be covered with insulation equivalent to that of the conductor. The use of identified manufactured splice insulators to cover wire to wire connections is recommended.” This is easily defined as recommending the use of splice kits, which we will be discussing later, while also allowing for alternate methods of insulating connections. Cover Opening Minimum Dimension Horsepower 1 and Smaller 1.5, 2 and 3 5 and 7.5 10 and 15 Millimeters 41 45 50 65 Inches 1.625 1.75 2 2.5 Useable Volume Minimum Centimeters3 170 275 365 595 Inches3 10.5 16.8 22.4 36.4 Figure 1 - Terminal Housings, Motors 11-Inch Diameter or Less 58 february/march 2008

Table of Contents Feed for the Digital Edition of Up Time Magazine- February/March 2008

Up Time Magazine- February/March 2008 Contents Upfront Upclose: Lessons Learned from the Walter Reed Story Information Technology: Parenting and Asset Performance Infrared: It's Alive! Lubrication: A Sense of Change Maintenance Management: PdM, Standardized Motor Testing: Being Well Connected Precision Maintenance: How to be Marketable Reliability: The Voyage of Wells Dairy Ultrasound: Two is Better Than One Vibration: Diagnosing a Cracked Shaft Upgrade: A Different Kind of Journey

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