Incorrect DHW Load Calculation

[lukeduran]

We provided two water heaters with a load fraction of 0.6 and 0.4 which sum to 1; however, we received an error back that said that the sum came out to 0.4.

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        "body": {
            "addressFull": "3504 Harbor Pointe Dr, Saint Joseph, MO 64506-4526",
            "addressComponents": {
                "addressLine1": "3504 Harbor Pointe Dr",
                "city": "Saint Joseph",
                "stateAbbreviation": "MO",
                "zipCode": "64506-4526"
            },
            "baseBuilding": {
                "buildingSummary": {
                    "yearBuilt": 1997,
                    "bedroomsCount": 4,
                    "averageCeilingHeight": 8,
                    "conditionedFloorArea": 4814
                },
                "enclosure": {
                    "attics": [
                        {
                            "floorAssemblyEffectiveRValue": 31,
                            "id": "attic-insulation-1"
                        }
                    ],
                    "foundations": [
                        {
                            "type": "basement unconditioned",
                            "id": "floor-and-foundation-insulation-1"
                        }
                    ],
                    "walls": [
                        {
                            "assemblyEffectiveRValue": 13,
                            "id": "wall-insulation-1"
                        }
                    ]
                },
                "systems": {
                    "hvac": {
                        "hvacHeatPumps": [
                            {
                                "systemType": "air-to-air",
                                "heatLoadFraction": 0.7,
                                "coolLoadFraction": 0.7,
                                "heatEfficiency": 8.8,
                                "coolEfficiency": 16.0,
                                "backupSystem": {},
                                "id": "heat-pump-systems-1"
                            },
                            {
                                "systemType": "air-to-air",
                                "heatLoadFraction": 0.3,
                                "coolLoadFraction": 0.3,
                                "heatEfficiency": 8.2,
                                "coolEfficiency": 14.0,
                                "backupSystem": {},
                                "id": "heat-pump-systems-2"
                            }
                        ]
                    },
                    "waterHeating": {
                        "waterHeatingSystems": [
                            {
                                "fuel": "natural gas",
                                "dhwLoadFraction": 0.6,
                                "id": "water-heating-1"
                            },
                            {
                                "fuel": "natural gas",
                                "dhwLoadFraction": 0.4,
                                "id": "water-heating-2"
                            }
                        ]
                    }
                }
            },
            "globalControls": {
                "debug": true,
                "includeInputs": true,
                "includeBase": true,
                "includeTypical": true,
                "useFixture": false,
                "resolution": [
                    "annual",
                    "monthly"
                ],
                "timelineStartDate": "2024-02-27",
                "timelineDurationInYears": 1,
                "units": {
                    "energyStandard": "MBtu",
                    "coal": "metric ton",
                    "electricity": "MBtu",
                    "fuelOil": "MBtu",
                    "naturalGas": "MBtu",
                    "propane": "MBtu",
                    "woodCord": "MBtu",
                    "woodPellets": "MBtu",
                    "monetary": "USD",
                    "emissions": "CO2"
                }
            }
        }
    },
    "response": {
        "headers": {
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            "Date": "Tue, 27 Feb 2024 19:26:44 GMT",
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            "X-Request-Id": "01hqp0a7znrx1r29eak9awdxat",
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        "body": {
            "globalControls": {
                "timelineStartDate": "2024-02-27",
                "debug": true,
                "includeInputs": true,
                "resolution": [
                    "monthly",
                    "annual"
                ],
                "includeBase": true,
                "includeTypical": true,
                "useFixture": false,
                "timelineDurationInYears": 1,
                "units": {
                    "monetary": "USD",
                    "electricity": "MBtu",
                    "naturalGas": "MBtu",
                    "woodPellets": "MBtu",
                    "propane": "MBtu",
                    "coal": "metric ton",
                    "emissions": "CO2",
                    "woodCord": "MBtu",
                    "energyStandard": "MBtu",
                    "fuelOil": "MBtu"
                }
            },
            "addressFull": "3504 Harbor Pointe Dr, Saint Joseph, MO 64506-4526",
            "baseBuilding": {
                "systems": {
                    "waterHeating": {
                        "waterHeatingSystems": [
                            {
                                "dhwLoadFraction": 0.6,
                                "fuel": "natural gas",
                                "id": "water-heating-1"
                            },
                            {
                                "dhwLoadFraction": 0.4,
                                "fuel": "natural gas",
                                "id": "water-heating-2"
                            }
                        ]
                    },
                    "hvac": {
                        "hvacHeatPumps": [
                            {
                                "heatLoadFraction": 0.7,
                                "heatEfficiency": 8.8,
                                "backupSystem": {},
                                "coolLoadFraction": 0.7,
                                "coolEfficiency": 16.0,
                                "systemType": "air-to-air",
                                "id": "heat-pump-systems-1"
                            },
                            {
                                "heatLoadFraction": 0.3,
                                "heatEfficiency": 8.2,
                                "backupSystem": {},
                                "coolLoadFraction": 0.3,
                                "coolEfficiency": 14.0,
                                "systemType": "air-to-air",
                                "id": "heat-pump-systems-2"
                            }
                        ]
                    }
                },
                "enclosure": {
                    "walls": [
                        {
                            "assemblyEffectiveRValue": 13,
                            "id": "wall-insulation-1"
                        }
                    ],
                    "foundations": [
                        {
                            "type": "basement unconditioned",
                            "id": "floor-and-foundation-insulation-1"
                        }
                    ],
                    "attics": [
                        {
                            "floorAssemblyEffectiveRValue": 31,
                            "id": "attic-insulation-1"
                        }
                    ]
                },
                "buildingSummary": {
                    "conditionedFloorArea": 4814,
                    "yearBuilt": 1997,
                    "bedroomsCount": 4,
                    "averageCeilingHeight": 8
                }
            },
            "addressComponents": {
                "zipCode": "64506-4526",
                "addressLine1": "3504 Harbor Pointe Dr",
                "stateAbbreviation": "MO",
                "city": "Saint Joseph"
            },
            "errors": [
                {
                    "message": "[\"Warning: No dishwasher specified, the model will not include dishwasher energy use.\" \"Error: /tmp/modeling-api/dir2/NORMAL/20240227192255351062365/299259200_BASE.xml: Expected FractionDHWLoadServed to sum to 1, but calculated sum is 0.4.\"]",
                    "code": "openstudio-creating-input-unsuccessful"
                }
            ]
        }
    }
}```

[kellyatradiantlabs]

@lukeduran Thanks for sharing and apologies for the confusion here. We unfortunately only support single systems at this time. This limitation is not currently included in our documentation, so we will use this ticket to do so! It is on our roadmap to support multiple systems in the future. They create additional complexity when automatedMeasures are at play, so the use of multiple systems will likely be an advanced feature.

[kellyatradiantlabs]

See here in the documentation the limit of array size 1. We intend to support multiple systems in a future release.