Find an example file that is specific to the object in question. In this example, FourPipeBeamLargeOffice.idf. Then search for the object. The notable connections in this object are the air and water node names.

Note that there are 2 air nodes, and 2 sets of water nodes. There are no coils in this object, they are inferred.

  AirTerminal:SingleDuct:ConstantVolume:FourPipeBeam,
    Core_bottom 4pipe Beam, !- Name
    HVACOperationSchd , !- Primary Air Availability Schedule Name
    HVACOperationSchd , !- Cooling Availability Schedule Name
    HVACOperationSchd , !- Heating Availability Schedule Name
    Core_bottom 4pipe Beam Inlet Node Name , !- Primary Air Inlet Node Name
    Core_bottom 4pipe Beam Outlet Node Name , !- Primary Air Outlet Node Name
    Core_bottom 4pipe Beam CW Inlet Node , !- Chilled Water Inlet Node Name
    Core_bottom 4pipe Beam CW Outlet Node , !- Chilled Water Outlet Node Name
    Core_bottom 4pipe Beam HW Inlet Node , !- Hot Water Inlet Node Name
    Core_bottom 4pipe Beam HW Outlet Node, !- Hot Water Outlet Node Name
    AUTOSIZE , !- Design Primary Air Volume Flow Rate
    AUTOSIZE , !- Design Chilled Water Volume Flow Rate
    AUTOSIZE , !- Design Hot Water Volume Flow Rate
    AUTOSIZE , !- Zone Total Beam Length
    0.036 , !- Rated Primary Air Flow Rate per Meter
    597 , !- Rated Beam Cooling Capacity per Meter
    10.0 , !- Rated Cooling Room Air Chilled Water Temperature Difference
    5.2E-5 , !- Rated Chilled Water Volume Flow Rate per Meter
    CapModFuncOfTempDiff, !- Beam Cooling Capacity Temperature Difference Modification Factor Curve or Table Name
    CoolCapModFuncOfSAFlow, !- Beam Cooling Capacity Air Flow Modification Factor Curve or Table Name
    CapModFuncOfWaterFlow, !- Beam Cooling Capacity Chilled Water Flow Modification Factor Curve or Table Name
    1548 , !- Rated Beam Heating Capacity per Meter
    27.8, !- Rated Heating Room Air Hot Water Temperature Difference
    5.2E-5, !- Rated Hot Water Volume Flow Rate per Meter
    CapModFuncOfTempDiff, !- Beam Heating Capacity Temperature Difference Modification Factor Curve or Table Name
    HeatCapModFuncOfSAFlow, !- Beam Heating Capacity Air Flow Modification Factor Curve or Table Name
    CapModFuncOfWaterFlow; !- Beam Heating Capacity Hot Water Flow Modification Factor Curve or Table Name

Now look at the induction unit example file. 5ZoneFPIU.idf.

This objects has 3 air nodes, 2 sets of water nodes, and a mixer object.

  AirTerminal:SingleDuct:ConstantVolume:FourPipeInduction,
    SPACE1-1 FPIU,           !- Name
    ReheatCoilAvailSched,    !- Availability Schedule Name
    autosize,                !- Maximum Total Air Flow Rate {m3/s}
    1.0,                     !- Induction Ratio
    SPACE1-1 ATU Supply Node,!- Supply Air Inlet Node Name
    SPACE1-1 ATU Induc Node, !- Induced Air Inlet Node Name
    SPACE1-1 In Node,        !- Air Outlet Node Name
    SPACE1-1 HW Coil Water In Node,  !- Hot Water Inlet Node Name
    SPACE1-1 CW Coil Water In Node,  !- Cold Water Inlet Node Name
    Coil:Heating:Water,      !- Heating Coil Object Type
    SPACE1-1 HW Coil,        !- Heating Coil Name
    autosize,                !- Maximum Hot Water Flow Rate {m3/s}
    0.0,                     !- Minimum Hot Water Flow Rate {m3/s}
    0.002,                   !- Heating Convergence Tolerance
    Coil:Cooling:Water,      !- Cooling Coil Object Type
    SPACE1-1 CW Coil,        !- Cooling Coil Name
    autosize,                !- Maximum Cold Water Flow Rate {m3/s}
    0.0,                     !- Minimum Cold Water Flow Rate {m3/s}
    0.002,                   !- Cooling Convergence Tolerance
    SPACE1-1 ATU Mixer;      !- Zone Mixer Name

Here's how I would make this change.

Using a text editor:

1) find the coils and mixer specified in the induction unit object input and comment them out. Don't delete them yet since you will need the water node names.

Search for the name of the heating coil, SPACE1-1 HW Coil to find this object.

!  Coil:Heating:Water,
!    SPACE1-1 HW Coil,        !- Name
!    ReheatCoilAvailSched,    !- Availability Schedule Name
!    autosize,                !- U-Factor Times Area Value {W/K}
!    autosize,                !- Maximum Water Flow Rate {m3/s}
!    SPACE1-1 HW Coil Water In Node,  !- Water Inlet Node Name
!    SPACE1-1 HW Coil Water Out Node,  !- Water Outlet Node Name
!    SPACE1-1 ATU Induc Node, !- Air Inlet Node Name
!    SPACE1-1 HW Coil Air Out Node,  !- Air Outlet Node Name
!    UFactorTimesAreaAndDesignWaterFlowRate,  !- Performance Input Method
!    autosize,                !- Rated Capacity {W}
!    82.2,                    !- Rated Inlet Water Temperature {C}
!    16.6,                    !- Rated Inlet Air Temperature {C}
!    71.1,                    !- Rated Outlet Water Temperature {C}
!    32.2,                    !- Rated Outlet Air Temperature {C}
!    ;                        !- Rated Ratio for Air and Water Convection

Search for the name of the cooling coil, SPACE1-1 CW Coil to find this object.

!  Coil:Cooling:Water,
!    SPACE1-1 CW Coil,        !- Name
!    CWCoilAvailSched,        !- Availability Schedule Name
!    autosize,                !- Design Water Flow Rate {m3/s}
!    autosize,                !- Design Air Flow Rate {m3/s}
!    autosize,                !- Design Inlet Water Temperature {C}
!    autosize,                !- Design Inlet Air Temperature {C}
!    autosize,                !- Design Outlet Air Temperature {C}
!    autosize,                !- Design Inlet Air Humidity Ratio {kgWater/kgDryAir}
!    autosize,                !- Design Outlet Air Humidity Ratio {kgWater/kgDryAir}
!    SPACE1-1 CW Coil Water In Node,  !- Water Inlet Node Name
!    SPACE1-1 CW Coil Water Out Node,  !- Water Outlet Node Name
!    SPACE1-1 HW Coil Air Out Node,  !- Air Inlet Node Name
!    SPACE1-1 CW Coil Air Out Node,  !- Air Outlet Node Name
!    SimpleAnalysis,          !- Type of Analysis
!    CrossFlow;               !- Heat Exchanger Configuration

Search for the name of the zone mixer, SPACE1-1 ATU Mixer to find this object.

!  AirLoopHVAC:ZoneMixer,
!    SPACE1-1 ATU Mixer,      !- Name
!    SPACE1-1 In Node,        !- Outlet Node Name
!    SPACE1-1 ATU Supply Node,!- Inlet 1 Node Name
!    SPACE1-1 CW Coil Air Out Node;  !- Inlet 2 Node Name

2) copy the FourPipeBeam object just below the induction unit. Find the induction unit again and comment it out.

!  AirTerminal:SingleDuct:ConstantVolume:FourPipeInduction,
!    SPACE1-1 FPIU,           !- Name
!    ReheatCoilAvailSched,    !- Availability Schedule Name
!    autosize,                !- Maximum Total Air Flow Rate {m3/s}
!    1.0,                     !- Induction Ratio
!    SPACE1-1 ATU Supply Node,!- Supply Air Inlet Node Name
!    SPACE1-1 ATU Induc Node, !- Induced Air Inlet Node Name
!    SPACE1-1 In Node,        !- Air Outlet Node Name
!    SPACE1-1 HW Coil Water In Node,  !- Hot Water Inlet Node Name
!    SPACE1-1 CW Coil Water In Node,  !- Cold Water Inlet Node Name
!    Coil:Heating:Water,      !- Heating Coil Object Type
!    SPACE1-1 HW Coil,        !- Heating Coil Name
!    autosize,                !- Maximum Hot Water Flow Rate {m3/s}
!    0.0,                     !- Minimum Hot Water Flow Rate {m3/s}
!    0.002,                   !- Heating Convergence Tolerance
!    Coil:Cooling:Water,      !- Cooling Coil Object Type
!    SPACE1-1 CW Coil,        !- Cooling Coil Name
!    autosize,                !- Maximum Cold Water Flow Rate {m3/s}
!    0.0,                     !- Minimum Cold Water Flow Rate {m3/s}
!    0.002,                   !- Cooling Convergence Tolerance
!    SPACE1-1 ATU Mixer;      !- Zone Mixer Name

Now paste in the new FourPipeBeam object just below this point in the file. Copy the name of the induction unit into the new FourPipeBeam object. Copy the 2 air node names for supply air inlet and air outlet into the air nodes below. Do the same for the cooling and heating coil node names. Also copy the name of the availability schedule to the appropriate 3 inputs below, or create your own schedules. Notice we are not changing node names, that makes things much more complicated than they need to be. You can change them later if you like.

  AirTerminal:SingleDuct:ConstantVolume:FourPipeBeam,
    SPACE1-1 FPIU, !- Name
    ReheatCoilAvailSched, !- Primary Air Availability Schedule Name
    ReheatCoilAvailSched, !- Cooling Availability Schedule Name
    ReheatCoilAvailSched, !- Heating Availability Schedule Name
    SPACE1-1 ATU Supply Node, !- Primary Air Inlet Node Name
    SPACE1-1 In Node, !- Primary Air Outlet Node Name
    SPACE1-1 CW Coil Water In Node, !- Chilled Water Inlet Node Name
    SPACE1-1 CW Coil Water Out Node, !- Chilled Water Outlet Node Name
    SPACE1-1 HW Coil Water In Node, !- Hot Water Inlet Node Name
    SPACE1-1 HW Coil Water Out Node, !- Hot Water Outlet Node Name
    AUTOSIZE , !- Design Primary Air Volume Flow Rate
    AUTOSIZE , !- Design Chilled Water Volume Flow Rate
    AUTOSIZE , !- Design Hot Water Volume Flow Rate
    AUTOSIZE , !- Zone Total Beam Length
    0.036 , !- Rated Primary Air Flow Rate per Meter
    597 , !- Rated Beam Cooling Capacity per Meter
    10.0 , !- Rated Cooling Room Air Chilled Water Temperature Difference
    5.2E-5 , !- Rated Chilled Water Volume Flow Rate per Meter
    CapModFuncOfTempDiff, !- Beam Cooling Capacity Temperature Difference Modification Factor Curve or Table Name
    CoolCapModFuncOfSAFlow, !- Beam Cooling Capacity Air Flow Modification Factor Curve or Table Name
    CapModFuncOfWaterFlow, !- Beam Cooling Capacity Chilled Water Flow Modification Factor Curve or Table Name
    1548 , !- Rated Beam Heating Capacity per Meter
    27.8, !- Rated Heating Room Air Hot Water Temperature Difference
    5.2E-5, !- Rated Hot Water Volume Flow Rate per Meter
    CapModFuncOfTempDiff, !- Beam Heating Capacity Temperature Difference Modification Factor Curve or Table Name
    HeatCapModFuncOfSAFlow, !- Beam Heating Capacity Air Flow Modification Factor Curve or Table Name
    CapModFuncOfWaterFlow; !- Beam Heating Capacity Hot Water Flow Modification Factor Curve or Table Name

3) Now go find the induction node name, SPACE1-1 ATU Induc Node. In this example file, it's found in a node list. Comment out the node list.

!  NodeList,
!    SPACE1-1 Exh Nodes,      !- Name
!    SPACE1-1 ATU Induc Node; !- Node 1 Name

Which connects to the zone here. Copy the exhaust node input, comment one of these, and delete the exhaust node name.

  ZoneHVAC:EquipmentConnections,
    SPACE1-1,                !- Zone Name
    SPACE1-1 Eq,             !- Zone Conditioning Equipment List Name
    SPACE1-1 In Nodes,       !- Zone Air Inlet Node or NodeList Name
!    SPACE1-1 Exh Nodes,      !- Zone Air Exhaust Node or NodeList Name
    ,      !- Zone Air Exhaust Node or NodeList Name
    SPACE1-1 Node,           !- Zone Air Node Name
    SPACE1-1 Out Node;       !- Zone Return Air Node Name

4) Now search for the name of the induction unit, SPACE1-1 FPIU. You will find this object.

  ZoneHVAC:AirDistributionUnit,
    SPACE1-1 ATU,            !- Name
    SPACE1-1 In Node,        !- Air Distribution Unit Outlet Node Name
    AirTerminal:SingleDuct:ConstantVolume:FourPipeInduction,  !- Air Terminal Object Type
    SPACE1-1 FPIU;           !- Air Terminal Name

Change the object name AirTerminal:SingleDuct:ConstantVolume:FourPipeInduction to AirTerminal:SingleDuct:ConstantVolume:FourPipeBeam

  ZoneHVAC:AirDistributionUnit,
    SPACE1-1 ATU,            !- Name
    SPACE1-1 In Node,        !- Air Distribution Unit Outlet Node Name
    AirTerminal:SingleDuct:ConstantVolume:FourPipeBeam,  !- Air Terminal Object Type
    SPACE1-1 FPIU;           !- Air Terminal Name

5) Now search for the hot water nodes and replace the heating coil type and name with the four pipe beam type and name.

  Branch,
    SPACE1-1 HW Branch,      !- Name
    0,                       !- Maximum Flow Rate {m3/s}
    ,                        !- Pressure Drop Curve Name
    AirTerminal:SingleDuct:ConstantVolume:FourPipeBeam,      !- Component 1 Object Type
    SPACE1-1 FPIU,        !- Component 1 Name
    SPACE1-1 HW Coil Water In Node,  !- Component 1 Inlet Node Name
    SPACE1-1 HW Coil Water Out Node,  !- Component 1 Outlet Node Name
    ACTIVE;                  !- Component 1 Branch Control Type

6) Do the same for the cooling coil.

  Branch,
    SPACE1-1 CW Branch,      !- Name
    0,                       !- Maximum Flow Rate {m3/s}
    ,                        !- Pressure Drop Curve Name
    AirTerminal:SingleDuct:ConstantVolume:FourPipeBeam,      !- Component 1 Object Type
    SPACE1-1 FPIU,        !- Component 1 Name
    SPACE1-1 CW Coil Water In Node,  !- Component 1 Inlet Node Name
    SPACE1-1 CW Coil Water Out Node,  !- Component 1 Outlet Node Name
    ACTIVE;                  !- Component 1 Branch Control Type

7) Finally, you will have to create performance curves for the following inputs. Just copy them from the example file, to your input file.

 CapModFuncOfTempDiff, !- Beam Cooling Capacity Temperature Difference Modification Factor Curve or Table Name
 CoolCapModFuncOfSAFlow, !- Beam Cooling Capacity Air Flow Modification Factor Curve or Table Name
 CapModFuncOfWaterFlow, !- Beam Cooling Capacity Chilled Water Flow Modification Factor Curve or Table Name
 CapModFuncOfTempDiff, !- Beam Heating Capacity Temperature Difference Modification Factor Curve or Table Name
 HeatCapModFuncOfSAFlow, !- Beam Heating Capacity Air Flow Modification Factor Curve or Table Name
 CapModFuncOfWaterFlow; !- Beam Heating Capacity Hot Water Flow Modification Factor Curve or Table Name

  Curve:Linear,  ! y = x
    CapModFuncOfTempDiff, !-Name
    0, !_ Coef Const
    1, !- Coef x
    0,  !- min x
    1.5, !- max x
    0.0 , !- min y
    1.5; ! max y

  Table:OneIndependentVariable,
    CoolCapModFuncOfSAFlow, !- Name
    quadratic,!- Curve Type
    EvaluateCurveToLimits,!- Interpolation Method
    0.714,!- min x
    1.2857,!- max x
    0.8234,!- min y
    1.1256,!- max y
    dimensionless, !-
    dimensionless, !- 
    , !- normalization ref
    0.714286, 0.823403,
    1.0,      1.0,
    1.2857,   1.1256;

  Table:OneIndependentVariable,
    CapModFuncOfWaterFlow, !- Name
    quadratic,!- Curve Type
    EvaluateCurveToLimits,!- Interpolation Method
    0.0,!- min x
    1.333333,!- max x
    0.0,!- min y
    1.04,!- max y
    dimensionless, !-
    dimensionless, !- 
     , !- normalization ref
    0.0,      0.0,
    0.05,     0.001,
    0.33333,  0.71,
    0.5,      0.85,
    0.666667, 0.92,
    0.833333, 0.97,
    1.0,      1.0,
    1.333333, 1.04;

  Table:OneIndependentVariable,
    HeatCapModFuncOfSAFlow, !- Name
    quadratic,!- Curve Type
    EvaluateCurveToLimits,!- Interpolation Method
    0.714,!- min x
    1.2857,!- max x
    0.8554,!- min y
    1.0778,!- max y
    dimensionless, !-
    dimensionless, !- 
    , !- normalization ref
    0.714286, 0.8554,
    1.0,      1.0,
    1.2857,   1.0778;

8) That's it. Check the error file to see if there are any other problems. I followed along in the induction unit example file and it runs with only report variable warnings. The converted file made with these steps is attached: change the extension back to idf before you run it.

You should run through this exercise yourself to get familiar with this procedure. Let me know if the file does not come through as a text file.