Compressed Air Best Practices - January 2009 - (Page 33)

Focus Industry ENERGY REBATES | 01/09 | As stated above, the corrected number 1 AWG conductor ampacity is insufficient for use with this application in 40 or 45 ºC ambient conditions. Utilizing the appropriate correction factors, the 40 ºC application would require a minimum copper conductor size of 1/0, and the 45 ºC application would require a minimum copper conductor size of 2/0 to meet minimum NEC requirements. Last but not least, NEC 310.15 (B) (2) (a), and the associated Table, reference additional conductor ampacity correction multipliers that must be applied if more than three current carrying conductors are to be installed in a single conduit (raceway). An example of this procedure is demonstrated as follows: p “Safety is the driving force in the determination of minimum recommended supply wire sizes for variable speed compressor packages.” Assume that a 460V, 135 kW compressor has package amperage of 265A for wire sizing. The minimum recommended 75 ºC copper supply wire size for six conductors (two parallel sets) in a single conduit is 3/0 AWG for 40 ºC ambient conditions. Based on the proper copper conductor ampacity corrections for ambient temperature and six conductors (two parallel sets) in a single conduit, the corrected combined ampacity of both sets of the 3/0 AWG copper conductors is 281.6A which meets or exceeds the wire sizing requirements (200A x 2 = 400A x 0.88 = 352A x 0.8 = 281.6 corrected conductor ampacity). The minimum recommended 75 ºC copper wire size for six conductors (two parallel sets) is 4/0 AWG for 45 ºC ambient conditions. Based on the proper copper conductor ampacity corrections for ambient temperature and six conductors (two parallel sets) in a single conduit, the corrected combined ampacity of both sets of the 4/0 AWG copper conductors is 301.76A which meets or exceeds the wire sizing requirements (230A x 2 = 460A x 0.82 = 377.2A x 0.8 = 301.76 corrected conductor ampacity). p p Again, the minimum recommended supply wire sizes should be determined based on personnel and equipment safety being of the utmost concern. The final decision on the proper supply wire size should be reached by a qualified electrical professional, after taking into account all installation site-specific variables such as the type of wire used, temperature rating of lowest rated terminal connection point, length of the required wire run, actual supply voltage, maximum permitted voltage drop, ambient temperature, etcetera. As you can plainly see, there are many variables to be taken into account to ensure a minimum level of personnel and equipment safety. Everyone benefits when safety is the priority! Gardner Denver Compressor Division, is a leading global manufacturer of rotary screw, reciprocating and PET air compressors, positive displacement blowers and vacuum pumps, offers expertise in air system design, evaluations and maintenance with remote monitoring capabilities. For more information, call 1-800-682-9868 or visit www.GardnerDenverProducts.com. www.airbestpractices.com 33 http://www.GardnerDenverProducts.com http://www.airbestpractices.com

Table of Contents Feed for the Digital Edition of Compressed Air Best Practices - January 2009

Compressed Air Best Practices - January 2009 Contents From the Editor Utility-Air News Compressed Air Audit of the Month: A Nitrogen Audit at Boeing Air Standards: New ASME & ISO Standards for Compressed Air System Assessments Energy Rebates Assist Industrial Sustainability Initiatives Seven Sustainability Projects for Industrial Energy Savings: Project #1: Lighting Optimization Minimum Supply Wire Size Recommendations for Compressor Packages Utilizing Variable Frequency Drives The Pneumatic Advantage: Pneumatics Bring Precision and Reliability to Furniture Industry Specialist Personal Productivity: Is Afternoon Fatigue Influencing Your Job Performance? The Explanation and Some Solutions. Resources for Energy Engineers: Training Calendar & Product Picks Wall Street Watch Advertiser Index Classifieds

Compressed Air Best Practices - January 2009

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