issue with example file: ASHRAE901_OfficeSmall_STD2019_Denver.idf

[KWSL]

Issue overview

We noticed an issue in this example file - the branch SHWSys1 Supply Equipment Branch has the SHWSys1 Water Heater and node connections defined, but the definition of the waterheater itself does not include the node connections. The file simulates with only a warning. The SVG shows the loop connections without the waterheater on the supply side of the loop.

I have EnergyPlus back to version 9.4 installed on this computer, and the example file shows the same pattern in that version as well.

Branch:

  Branch,
    SHWSys1 Supply Equipment Branch,  !- Name
    ,                        !- Pressure Drop Curve Name
    WaterHeater:Mixed,       !- Component 1 Object Type
    SHWSys1 Water Heater,    !- Component 1 Name
    SHWSys1 Pump-SHWSys1 Water HeaterNode,  !- Component 1 Inlet Node Name
    SHWSys1 Supply Equipment Outlet Node;  !- Component 1 Outlet Node Name

WaterHeater

   WaterHeater:Mixed,
    SHWSys1 Water Heater,    !- Name
    0.1514,                  !- Tank Volume {m3}
    SHWSys1 Water Heater Setpoint Temperature Schedule,  !- Setpoint Temperature Schedule Name
    2.0,                     !- Deadband Temperature Difference {deltaC}
    82.2222,                 !- Maximum Temperature Limit {C}
    Cycle,                   !- Heater Control Type
    11722.84,                !- Heater Maximum Capacity {W}
    ,                        !- Heater Minimum Capacity {W}
    ,                        !- Heater Ignition Minimum Flow Rate {m3/s}
    ,                        !- Heater Ignition Delay {s}
    electricity,             !- Heater Fuel Type
    1,                       !- Heater Thermal Efficiency
    ,                        !- Part Load Factor Curve Name
    571,                     !- Off Cycle Parasitic Fuel Consumption Rate {W}
    electricity,             !- Off Cycle Parasitic Fuel Type
    0.8,                     !- Off Cycle Parasitic Heat Fraction to Tank
    571,                     !- On Cycle Parasitic Fuel Consumption Rate {W}
    electricity,             !- On Cycle Parasitic Fuel Type
    ,                        !- On Cycle Parasitic Heat Fraction to Tank
    zone,                    !- Ambient Temperature Indicator
    ,                        !- Ambient Temperature Schedule Name
    CORE_ZN,                 !- Ambient Temperature Zone Name
    ,                        !- Ambient Temperature Outdoor Air Node Name
    1.205980747,             !- Off Cycle Loss Coefficient to Ambient Temperature {W/K}
    ,                        !- Off Cycle Loss Fraction to Zone
    1.205980747,             !- On Cycle Loss Coefficient to Ambient Temperature {W/K}
    ,                        !- On Cycle Loss Fraction to Zone
    4.048e-06,               !- Peak Use Flow Rate {m3/s}
    BLDG_SWH_SCH;            !- Use Flow Rate Fraction Schedule Name

Operating System (Multiple choices)

Windows

Operating System Version

Windows 11

Version of EnergyPlus

25.1.0

Unmethours link or helpdesk ticket number

N/A

Defect file

standard example files that come with EnergyPlus

[RKStrand]

I looked at this a bit today and it does log some warning messages in the .err file, but at the Warning level, they would be easy to miss amongst the numerous warnings that this file produces. I corrected the file by adding the appropriate node names to the WaterTank:Mixed object and this does result in some changes to the .htm output. It seems like this .idf should be fixed, but the questions are: 1. Should this have a higher level warning? 2. Should the water heater do any other sorts of checks to see if it can find the matching water heater elsewhere or something? @Myoldmopar and @mjwitte, thoughts?

[mjwitte]

@RKStrand This should be covered by the CompSets checking. What are the warnings you see? I know at the time we set that up, there was some uncertainty about whether there could be a legitimate configuration that didn't conform to the connection checking. However, in this case, if a parent object (i.e. Branch) registers a connection that is never complemented by the child component, that should be a severe/fatal.

[RKStrand]

@mjwitte Here is the error message that gets produced when the file does not have nodes defined in the WaterHeater:Mixed object but are defined in the Branch input. Here is what is being sent to the .err file by ReportLoopConnections:

** Warning ** Potential Node Connection Error for object WATERHEATER:MIXED, name=SHWSYS1 WATER HEATER
** ~~~ ** Node Types are still UNDEFINED -- See Branch/Node Details file for further information
** ~~~ ** Inlet Node : SHWSYS1 PUMP-SHWSYS1 WATER HEATERNODE
** ~~~ ** Outlet Node: SHWSYS1 SUPPLY EQUIPMENT OUTLET NODE

From what I can tell, the Branch input syntax is correct, but the WaterHeater:Mixed input fails to define the node names.

[mjwitte]

So, it would be interesting to see if changing only this particular warning to severe/fatal would trip up any of our test suite. As far as I know, there should never be any "UNDEFINED" node types if everything is connected properly.

[RKStrand]

@mjwitte Your wish is in the process of being granted. I just pushed a commit that turns this into a severe/fatal. Let's see what happens...