TM 5-3895-374-24-2 32. Set and check operation of: A) Low  and  high  gas  pressure  switches.    See  gas pressure   switch   manufacturer’s   instructions   for detailed procedures. Units with mercury switching device must be properly leveled. (1) For initial start up: Once  the  burner’s  normal  operational  gas pressure has been set, adjust the low and high gas pressure switches as follows: (a) Low    gas    pressure    switch.        With    the burner running, slowly close the main gas train  manual  shutoff  cock  and  adjust  the switch    to    open    its    circuit    when    the pressure   falls   below   its   normal   value. The   burner   will   shut   down.      Open   the manual  gas  shutoff  cock  to  the  full  open position and manually reset the Low Gas Pressure Switch.  The burner will restart. (b) High    gas    pressure    switch.        With    the burner   running,   adjust   the   switch   to   a point  where  the  switch  opens  its  circuit. The   burner   will   shut   down.      Manually reset  the  switch  and  readjust  the  cutout point to be made at the normal operating pressure, but to open if the pressure goes slightly above normal. B) All    burner    and    heat    exchanger    controls    and operating devices. C) Blower Combustion Air Flow Switch (1) Shut burner power off. (2) Disconnect    both    wires    at    the    air    flow switch  and  temporarily  clip  them  together. Make sure that they cannot ground against anything,  since  they  will  be  powered  with 110 Volts during the test. (3) Put a continuity meter across the common and   normally   open   terminals   on   the   air switch. (4) Close the gas train checking cock. (5) Start the blower motor.  The meter should read  electrical  continuity  as  soon  as  the blower starts. (6) Disconnect  the  blower  motor  lead  wire  or the  wire  which  energizes  coil  of  motor  re (starter), or open the main power disconnect switch to the  burner.    Within  4 to 5 seconds after the blower motor is  de- energized,   the   meter   should   indicate   an open air flow switch circuit (no continuity). (7) If   the   switch   does   not   open   in   4   to   5 seconds,  readjust  accordingly.    Turn  the air flow switch adjustment screw clockwise to    shorten    cut-off    response    time,    and counterclockwise to lengthen cut-off response time. (8) Turn  the  burner  power  off.    Remove  the shorting   clip   from   the   two   disconnected wires and let them hang loose.  (They will be   powered   with   110   Volts,   so   don’t   let them ground out.) (9) Open  the  gas  train  checking  cock.    Turn the burner on. With the wires disconnected,  the  burner  should  go  into  a purge  cycle,  although  neither  the  ignition nor   the   main   fuel   valve   circuits   will   be energized.    If  they  do  energize,  there  is  a wiring problem.  Correct as required. (10) Turn  power  off.    Reconnect  the  air  flow switch     wires     to     the     air     flow     switch terminals.    Place  burner  back  into  normal operation. 33. The “Owner's Operating Instructions,” page 43 of this manual, should be posted in a clearly visible location close to the burner. 34. If   the   burner   operation   is   abnormal,   refer   to Section   7,   “Trouble   Shooting   Suggestions,”   as well  as  trouble  shooting  information  included  in the    flame    safeguard    manufacturer's    bulletin shipped   with   the   burner.      It   is   also   strongly suggested that all test procedures outlined in the flame safeguard control manufacturer's bulletin be conducted. 35. Complete  the  “Burner  Start  Up  Information  and Test Data” sheets on pages 41 and 42. 6.  OIL START UP Refer to page 21, “General Start Up Procedure - All Fuels” and to Section  3  for  mechanical  operation  detail  of  specific   mode   of operation.  Combination Gas/Oil systems  should  also  refer  to  page  22,  “Information  on  Fuel/Air Modes of Operation for Combination Gas/Oil Units.” General Information Power  Flame  Type  C  oil  burners  are  of  the  pressure  atomizing forced  draft  type,  using  a  single  simplex  or  bypass  type  nozzle system.  On/Off burners use a simplex nozzle.  Fixed air low fire start  burners  use  a  simplex  nozzle  with  a  bypass  valve  to  allow reduced   oil   nozzle   pressures   at   light   off.      Low/High/Off   and Low/High/Low burners have movable air dampers and may use a single  simplex  or  bypass  type  oil  nozzle  with  a  bypass  valve  to allow reduced oil pressures at light off and at low fire.  Modulating burners  have  movable  air  dampers  and  use  a  single  simplex  or bypass  type  oil  nozzle  with  a  proportioning  metering  valve  in  the nozzle return line to allow modulated fuel inputs from low  to  high fire. Some  applications  may  require  the  burner  to  function  at  the  low end of its rated capacity.  As a result, the two combustion air inlets may  supply  more  air  than  is  required  for  efficient  combustion.    It may therefore be desirable to operate the system using only one combustion  air  inlet  and  one  combustion  air  inlet  damper.    This may   be   accomplished   by   removing   cross   connecting   linkage between   dampers   and   locking   the   unused   damper   in   a   fixed position. One way of locking the damper is to use a 10-24 machine screw through the hole in the linkage arm, and drill and tap the air inlet housing  or  use  two  nuts  on  the  screw  and  let  the  screw  bear against the air inlet housing.  Air diffuser movement (fore and aft) may be necessary to produce the best flame pattern or smoothest operation.    See  page  20,  “Gas,  Oil  or  Gas/Oil  Burners  Diffuser Adjustment,” for further information. Gas  and  Gas/Oil  burners  for  Scotch  marine  and  other  selected applications   incorporate   a   gas/air   premix   adjustment.      This adjustment is identified by diametrically opposed adjustment knobs on  the  blast  tube.    See  page  20,  “Gas  or  Gas/Oil  Burner  and Fuel/Air Premix Adjustment” for further information. (page 3 - 978)