{
  "version": "1.0",
  "calculator": {
    "id": "radiator-flow-temperature",
    "title": "Radiator flow temperature",
    "summary": "Works out what flow temperature a radiator needs for its room, and the Heat Emitter Guide star rating that follows.",
    "tier": "advanced",
    "description": "Work out the flow temperature a heat pump must produce to heat a room through a\ngiven radiator, and the resulting MCS Heat Emitter Guide star rating, following section 4 of MGD 007.\n\nThis is the calculation that decides whether a heat pump will be cheap or expensive to run. A heat\npump's efficiency falls as the water temperature rises, by roughly two to three per cent per degree,\nand the temperature it must produce is set by the radiators, not by the machine.\n\nSupply the room's design heat loss in watts, from a room-by-room calculation, and the rated output of\nthe radiator in that room. British catalogues normally quote at a mean-water-to-air difference of 50 K;\nif yours quotes 60, say so and the figure is restated.\n\nThe result gives the oversize factor, which is the radiator's output at 50 K divided by the room's heat\nloss, and converts it to a required flow temperature through the BS EN 442 output law. Star ratings run\nfrom 0 to 6, one star per five degrees of flow temperature, with six stars at 35 degrees.\n\nRun this for every room. A house runs at the flow temperature its worst room demands, so one undersized\nradiator sets the running cost for the whole house.",
    "standard": "MGD 007",
    "category": "heat-pumps",
    "webPath": "/calculators/radiator-flow-temperature",
    "example": {
      "roomHeatLossW": 976,
      "radiatorOutputW": 1938,
      "ratedAtDeltaT": 50,
      "roomTemp": 21,
      "systemDeltaT": 5
    },
    "inputSchema": {
      "type": "object",
      "properties": {
        "roomHeatLossW": {
          "type": "number",
          "description": "The room's design heat loss in watts, from a room-by-room heat loss calculation. Required."
        },
        "radiatorOutputW": {
          "type": "number",
          "description": "Rated output of the radiator or radiators in that room, in watts, at the catalogue temperature. Required."
        },
        "ratedAtDeltaT": {
          "type": "number",
          "description": "The mean-water-to-air temperature difference the rated output was quoted at. British catalogues normally quote 50; some older ones quote 60. Defaults to 50."
        },
        "roomTemp": {
          "type": "number",
          "description": "Internal design temperature of the room in Celsius. Defaults to 21."
        },
        "systemDeltaT": {
          "type": "number",
          "description": "Designed drop in water temperature between flow and return, in kelvin. Heat pump systems commonly use 5; boiler systems used 10 or 20. Defaults to 5."
        }
      },
      "required": [
        "roomHeatLossW",
        "radiatorOutputW"
      ],
      "additionalProperties": false
    },
    "outputSchema": {
      "type": "object",
      "properties": {
        "roomHeatLossW": {
          "type": "number"
        },
        "radiatorOutputW": {
          "type": "number"
        },
        "ratedAtDeltaT": {
          "type": "number"
        },
        "outputAtDeltaT50": {
          "type": "number",
          "description": "The radiator's output restated at a mean-water-to-air difference of 50 K, so oversize factors are comparable between catalogues."
        },
        "oversizeFactor": {
          "type": "number",
          "description": "Radiator output at 50 K divided by the room's heat loss. The single number the Heat Emitter Guide turns into a star rating."
        },
        "meanWaterTemp": {
          "type": "number",
          "description": "Average of flow and return temperature needed to deliver the room's heat loss through this radiator."
        },
        "flowTemperature": {
          "type": "number",
          "description": "The flow temperature the heat pump must produce, in Celsius."
        },
        "returnTemperature": {
          "type": "number"
        },
        "starRating": {
          "type": "integer",
          "description": "Temperature star rating from the MCS Heat Emitter Guide, 0 to 6. More stars mean a lower flow temperature and a more efficient system."
        },
        "starRatingLabel": {
          "type": "string"
        },
        "verdict": {
          "type": "string"
        },
        "outputAtDesignFlowW": {
          "type": "number",
          "description": "What this radiator actually gives at the flow temperature worked out here."
        },
        "radiatorOutputForFiveStarsW": {
          "type": "number",
          "description": "The radiator output at 50 K that would reach a five star rating, meaning a 40 degree flow temperature."
        },
        "method": {
          "type": "string"
        },
        "references": {
          "type": [
            "null",
            "array"
          ],
          "items": {
            "type": "object",
            "properties": {
              "document": {
                "type": "string"
              },
              "title": {
                "type": "string"
              },
              "url": {
                "type": "string"
              },
              "clause": {
                "type": "string"
              }
            },
            "required": [
              "document",
              "title",
              "url"
            ],
            "additionalProperties": false
          }
        },
        "notes": {
          "type": [
            "null",
            "array"
          ],
          "items": {
            "type": "string"
          }
        }
      },
      "required": [
        "roomHeatLossW",
        "radiatorOutputW",
        "ratedAtDeltaT",
        "outputAtDeltaT50",
        "oversizeFactor",
        "meanWaterTemp",
        "flowTemperature",
        "returnTemperature",
        "starRating",
        "starRatingLabel",
        "verdict",
        "outputAtDesignFlowW",
        "radiatorOutputForFiveStarsW",
        "method",
        "references",
        "notes"
      ],
      "additionalProperties": false
    }
  },
  "url": "https://ampworth.com/api/v1/calculators/radiator-flow-temperature",
  "webUrl": "https://ampworth.com/calculators/radiator-flow-temperature",
  "exampleUrl": "https://ampworth.com/api/v1/calculators/radiator-flow-temperature?roomHeatLossW=976\u0026radiatorOutputW=1938\u0026ratedAtDeltaT=50\u0026roomTemp=21\u0026systemDeltaT=5",
  "method": "POST",
  "contentType": "application/json",
  "notice": "These calculators follow the published MCS methods, for understanding a system and checking a quotation. Anything that gets installed still needs a design and a site survey from a certified installer."
}