3.   The  carbon  monoxide  gas  present  in  the  exhaust of  the  engine  is  extremely  poisonous.  Under  no circumstances should this gas be allowed to collect in a closed room; therefore, means have to be provided to discharge the engine exhaust to the outdoors. Exhaust can be vented by extending the exhaust pipe through the wall or roof of the building. Support the exhaust pipe and make certain that there is no obstruction and avoid right-angle bends, ifpossible. Also, whenever possible, arrange  the  exhaust  system  so  that  the  piping  slopes away from the engine. In this way, condensation will not drain back into the cylinders. If the exhaust pipe should have to be installed so that loops or traps are necessary, a drain cock should be placed at the lowest point of the system. All joints have to be perfectly tight; and where the exhaust pipe passes through the wall, you have  to  prevent  the  discharged  gas  from  returning  along the outside of the pipe back into the building. Exhaust piping inside the building has to be covered with insulation capable of withstanding a temperature of 1500°F. After the generating units have been set in place and  bolted  down,  Builders  then  can  proceed  to  erect  the building, using the necessary information provided by the CEs. Generator Set Inspection After  setting  up  a  portable  generator,  your  crew must do some preliminary work before placing the generator in operation. First, they should make an overall visual inspection of the generator. Have them look for broken or loose electrical connections, bolts, and cap screws; and see that the ground terminal wire (No. 6 AWG minimum ) is properly connected to the ground rod/grounding system. Check the technical manual furnished with the generator for wiring diagrams, voltage  outputs,  feeder  connections,  and  prestart preparation. If you find any faults, you should correct them  immediately. Generator  Connections When you install a power plant that has a dual- voltage alternator unit, make certain that the stator coil leads  are  properly  connected  to  produce  the  voltage required by the equipment. Proper grounding is also a necessity for personnel safety  and  for  prevention  of  unstable,  fluctuating generator  output. INTERNAL   LEADS.—The  voltage  changeover board permits reconnection of the generator phase windings to give all specified output voltages. One end of each coil of each phase winding runs from the generator through an instrumentation and a static exciter current transformer to the reconnection panel. This routing assures current sensing in each phase regardless of voltage connection at the reconnection board  assembly.  The  changeover  board  assembly  is equipped with a voltage change board to facilitate conversion  to  120/208  or  240/416  generator  output voltage.  Positioning  of  the  voltage  change  board connects two coils of each phase in series or in parallel. In parallel, the output is 120/208; in series, the output is 240/416 volts ac. The terminals on the changeover board assembly for connection to the generator loads are numbered according to the particular coil end of each  phase  of  the  generator  to  ensure  proper connections. Remember that you are responsible for the proper operation  of  the  generating  unit;  therefore,  proceed with caution on any reconnection job. Study the wiring diagrams of the plant and follow the manufacturer’s instructions to the letter. Before you start the plant up and   close   the   circuit   breaker,   double-check   all connections. GROUNDING.—It is imperative that you solidly ground all electrical generators operating at 600 volts or less. The ground can be, in order of preference, an underground metallic water piping system, a driven metal rod, or a buried metal plate. A ground rod has to have a minimum diameter of 5/8 inch if solid and 3/4 inch if pipe, and it has to be driven to a minimum of 8 feet. A ground plate has to be a minimum of 2 square feet and be buried at a minimum depth of 2 l/2 feet. For the ground lead, use No. 6 AWG copper wire and bolt or clamp it to the rod, plate, or piping system. Connect the other end of the ground lead to the generator set ground stud. The National Electrical Code^® states that a single electrode consisting of a rod, pipe, or plate that does not have a resistance to ground of 25 ohms or less will be augmented by additional electrodes. Where multiple rod, pipe, or plate electrodes are installed to meet the requirements, they are required to be not less than 6 feet apart. It  is  recommended  that  you  perform  an  earth resistance test before you connect the generator to ground. This test will determine the number of ground rods required to meet the requirements, or it may be necessary to construct a ground grid. 3-5