Laboratories  (UL)  tests  various  electrical  fixtures and devices to determine if they meet minimum specification  and  safety  requirements  as  set  up  by UL. Those fixtures and devices that are approved may  then  bear  UL  labels. Permit In  the  SEABEEs,  utility  drawings  (both mechanical and electrical) are thoroughly reviewed before an excavation (or digging) permit is granted and  issued  to  the  project  subcontractor.  Such action  minimizes  the  hazards  to  personnel  and underground  structures  during  the  construction process. All of the minor design changes and field adjustments   must   be   noted   and   reflected   on as-built  and  working  drawings.  Therefore,  close coordination   and   cooperation   must   develop within  and  among  all  of  the  parties  involved  in the   project   to   maintain   periodic   checks   on red-lined  prints  so  that  information  can  be compared  and  verified  as  up  to  date. ELECTRICAL  SYMBOLS The conventions used on the electrical plan are SYMBOLS  that  indicate  the  general  layout,  units, related   equipment,   fixtures   and   fittings,   and routing and interconnection of various electrical wiring.    The   most   common   types   of   symbols used   in   electrical   drawings   are   shown   in figure 9-23. To see additional or special symbols, refer to the appendix section of this book and/or to  ANSI  Y32.9. To draw in electrical symbols in an electrical drawing,  as  in  drawing  a  mechanical  plan,  it  is best  to  use  templates.  For  example,  a  wiring symbol is generally drawn as a single line but with slanting  “tick  marks”  to  indicate  the  number  of wires in an electrical circuit. EXTERIOR  ELECTRICAL LAYOUT  (PLAN) Exterior  distribution  lines  (or  network)  deliver electrical  power  from  the  source  (generating station  or  transmission  substation)  to  various points of use. Figure 9-24 shows a typical layout, extracted   from   NAVFAC   P-437,   Facilities Harming Guide, of an exterior electrical network of buildings for a 100-man camp. This layout, in condensed  form,  shows  a  site  plan  of  the  camp area  with  facilities  and  the  location  of  the electrical   component   system.   Included   in   the electrical plan is a list of facilities (upper right- hand  corner  of  fig.  9-24)  that  describes  the corresponding item symbol, facility number, and quantity.  An  electrical  load  data  table  is  also included in the drawing. As  an  EA,  you  will  be  called  upon  to  trace, modify,  revise,  and  even  review  the  workability of the drawing. It is therefore to your advantage not  only  to  study  and  become  familiar  with  the electrical  plans,  but  also  to  gain  a  working knowledge  of  how  the  system  works.  NAVFAC P-437  offers  a  wide  variety  of  plans,  drawings, and  applications  for  the  Advanced  Base  Func- tional   Component   (ABFC)   System   for   use   in SEABEE   construction. INTERIOR  ELECTRICAL LAYOUT   (PLAN) As  we  mentioned  earlier,  the  electrical information  on  exterior  electrical  distribution  is generally shown in the regular site or plot plan. The  INTERIOR  ELECTRICAL  LAYOUT,  how- ever,  is,  for  small  buildings,  drawn  into  a  print made  from  the  floor  plan.  On  larger  projects, additional separate drawing sheets are necessary to  accommodate  detailed  information  needed  to meet  construction  requirements. Figure  9-25  shows  an  electrical  layout  of  a typical public works shop. Once again, note that the electrical information is superimposed on an outline taken from an architectural floor plan. In addition  to  the  list  of  assemblies  and  electrical load table, a wiring diagram and panel schedule of a 225-A, three-phase circuit breaker is drawn. The  underground  service  entrance  (item  10  on  the list of assemblies) delivers a four-wire, 120/208-V power  into  the  building.  Lighting  circuits  use  a three-wire,  No.  12  AWG  (TW). The  following  basic  steps  are  suggested  to guide   you   in   the   development   of   an   interior electrical  plan: 1. Show the location of the service panel and its rating in amps. 2.  Show  all  of  the  wall  and  ceiling  outlets. 3.  Show  all  of  the  special-purpose  outlets, such  as  telephones,  communications,  doorbells, and  so  forth. 4.  Show  all  of  the  switches  and  their  outlet connections. 5.  Show  convenience  outlets. 6.   If   required, complete   a   schedule   of electrical  fixtures,  symbols,  legends,  and  notes necessary to clarify any special requirements in the   drawing   that   are   not   stipulated   in   the specifications. The  steps  suggested  above  can  be  put  to practice in the next chapter following mastery of civil  and  architectural  drawings. 9-17