INSTALL SERVICE-ENTRANCE SYSTEMS

SUBCOURSE ARMY ENGINEER SCHOOL SERVICE SYSTEMS SERVICE SYSTEMS Number EN5141 B States Army Engineer School Leonard Wood Missouri 65473 Credit Hours Date June 1999 OVERVIEW subcourse is part of Soldier Training Publication STP 5 51R12 SM TG Install Service Entrance It is designed to teach the knowledge and skills necessary to perform tasks related to installing SE systems The subcourse is presented in two lessons each corresponding to a learning objective as indicated below are no prerequisites for this subcourse subcourse reflects the doctrine which was current at the time the subcourse was prepared In your work situation always refer to the latest official publications otherwise stated the masculine gender of singular pronouns is used to refer to both men and LEARNING OBJECTIVE will learn the procedures used to install SE systems will be given the material in this subcourse and an Army Correspondence Program ACCP examination response sheet demonstrate competency of this task you must achieve a minimum of 70 on this subcourse OF CONTENTS Overview i Instructions iii and Certification Instructions iii 1 Overhead Entrance Systems 1 1 Exercise 1 20 Key and Feedback 1 22 2 Underground Service 2 1 Exercise 2 6 Key and Feedback 2 8 1 A List of Common Acronyms A 1 B Recommended Reading List B 1 Inquiry Sheets 1 ENTRANCE SYSTEMS Task 051 246 1102 DESCRIPTION this lesson you will learn to describe an overhead entrance system LEARNING OBJECTIVE will learn the procedures used to install an overhead entrance system will be given subcourse booklet EN5141 and an ACCP examination response You will work at your own pace and in your own selected environment no supervision will correctly answer practice exercise questions at the end of this lesson material contained in this lesson was derived from STP 5 51R12 SM TG and 5 424 entrance systems are the conductors and the equipment used for the control and protection of circuits equipment and personnel The SE is the end of the interior electrical system This will teach you how to describe an overhead entrance system conductors from the power pole to the building are called service drops as shown in Figure 1 1 1 2 The minimum height of a service drop above the ground and on the building is determined by location 1 1 Clearances for a service drop foot traffic areas 10 feet of vertical clearance is necessary for service drops supported and on a ground messenger having 150 volts to ground between the current carrying conductors 1 2 Remember the 10 foot minimum clearance is measured from the lowest point of the SE 1 2 Service drop above a foot traffic area residential property driveways and areas not subject to truck traffic 12 feet of vertical clearance maintained for conductors having 300 volts to ground Figure 1 3 1 3 Service drop above residential property subject to truck traffic 300 volts to ground residential property driveways and commercial property not subject to truck traffic 15 feet of clearance is maintained for conductors having 600 volts to ground Figure 1 4 Automobiles small vehicles can clear an SE cable with a minimum clearance of 15 feet to ground 1 4 Service drop above residential property subject to truck traffic 600 volts to ground public streets and parking areas subject to truck traffic 18 feet of vertical clearance is required in 1 5 A 20 foot high load did not clear the service drop 1 5 A high load damaging a service drop a peaked roof having a 1 3 pitch or more an 18 inch vertical clearance is necessary when the between conductors is less than 300 volts and the SE is a mast within 48 inches of the roofs edge 1 6 1 6 Clearance between the roof and service drop 300 volts that carry more than 300 volts require an 8 foot vertical clearance Figure 1 7 1 7 Clearance between the roof and the drop 300 volts that are installed at the side of a window or below it must have a 3 foot clearance Figure 1 1 8 Conductor clearance from windows fire escapes porches or platforms conductors must have 3 feet of horizontal clearance from the and 10 feet of vertical clearance from the ground Figures 1 9 and 1 10 1 9 Fire escape platform clearance 1 10 Clearance above ground level Requirements Attachment of Service Drops back supports in walls that are not strong enough to support a service drop in adverse conditions snow or ice Figure 1 11 A 2 inch by 4 foot back support gives added strength to the wall 1 11 Back support installed in wall single cable system supports hot conductors and is hooked to the feed through dead end Figure 1 The cable that supports the service drop conductors is clamped by the feed through clamp and to the ground conductors The cable support is part of the ground system 1 12 Grounded messenger cable providing support bare neutral conductor is used as the messenger cable Figure 1 13 By wrapping the hot around the messenger cable all the weight of the service drop is on the uninsulated cable 1 13 Hot conductors wrapped around a neutral messenger cable a typical service drop cable the neutral conductor is used to attach the cable to the dead end Figure The feed through clamp is built so that the pull of the conductors makes the clamp tighter on the cable 1 14 Feed through clamp to the service spool drops are also dead ended to a building by using secondary racks Figure 1 15 When heavy drops are installed on buildings use secondary racks 1 15 Service drop attached to a secondary rack individual conductors are installed many of the installations are dead ended by using service made of porcelain Figure 1 16 One service spool is screwed or bolted to the wall 1 16 Service drop attached to service spools masts can dead end individual conductors and an insulator bracket is used for this purpose 1 17 An insulator bracket can also be used when service conductors are wrapped around a cable but feed through clamp will be required 1 17 Use of insulator brackets service masts use a single dead end bracket and a service cable Figure 1 18 This makes a neat Although time consuming to install a service mast is the best method for service 1 18 Insulator bracket with feed through clamp Requirements Installation Procedures cable Figure 1 19 has a flame retardant moisture resistant covering The neutral conductor or aluminum is twiste