The result of the Radiators module compares two numbers in every room: how much heat the radiators give at the water temperature you chose, and how much heat the room needs. This article says where the module gets both. Every radiator output carries its source in the result: "datasheet", "typical" or "assumed". Every room load comes from the heat loss calculation, from the estimate or from what you typed.
A radiator's output: three sources
"datasheet" - from the radiator's datasheet
Tick "I have the radiator's datasheet" on the radiator and fill in two fields:
- "Datasheet output at 75/65/20" - the radiator's output (in watts on the datasheet; the app shows Btu/h with imperial units) at a 167 °F (75 °C) flow, a 149 °F (65 °C) return and a 68 °F (20 °C) room. It is the first row of nearly every maker's datasheet. Type the output of the whole radiator at its height and length.
- "Exponent n" - the figure from the datasheet that says how fast the output falls as the water gets cooler. Leave it empty and the module uses n = 1.3.
This is the most certain output, because it is your radiator's own.
"typical" - the median of several makers' datasheets
Without a datasheet, a panel radiator with its type entered (10, 11, 20, 21, 22 or 33) gets a typical output. For every type and height we took the output of a 1000 mm radiator and its exponent n from several makers' public datasheets, and used the median. The output scales with the radiator's length. For a height between two heights in the datasheets, the module interpolates between them.
Typical means: an ordinary radiator of that type and height. Yours may give a little more or less. When a room's result is close to the line, check your radiator's datasheet and type its output.
"assumed" - when there is no data
When a radiator has no datasheet output and there is no typical data for it - a column or cast-iron radiator, the kind "Not sure", or a panel radiator with no type - the module counts it as a type 22 panel of its size. A towel warmer ("Towel rail") counts as half a type 11 panel of its size. A type 11, 22 or 33 panel radiator whose height is outside the typical data gets the same general output for its own type. Types 10, 20 and 21 at such a height get no output: the module counts them as 0 W and asks for the datasheet output, because an output borrowed from a type 22 would be several times too high. The exponent n is then 1.3. It is only an assumption so that the room has some output at all - for such a radiator type the datasheet output, or measure the radiator and choose its kind if you can.
The output at the chosen temperature
A datasheet gives the output at 75/65/20, and you check the radiator at another temperature, 122 °F (50 °C), say. The module converts the output with the radiator characteristic from EN 442:
Φ = Φn · (ΔT / ΔTn)^n
- Φn - the output at 75/65/20 (from the datasheet, typical or assumed),
- ΔTn - the excess temperature at 75/65/20, that is 50 K,
- ΔT - the excess at your temperatures: the mean of the flow and return temperatures minus the room temperature, as EN 442-2 defines it (at 55/45/20 °C, 30 K),
- n - the radiator's exponent.
The return temperature is the "Flow temperature" minus the "Flow-return difference" from Setup. The room temperature is the temperature typed on the room, and when there is none, the room's temperature from the heat loss calculation or the house's room temperature.
What this output leaves out: mounting factors (niche, cover, connection) and heat from pipes running through the room. The method line under the result and in the report says the same.
With the same characteristic the module finds, for every room, the lowest flow temperature at which its radiators are enough - the "Enough from" column. The highest of those is the house's temperature: "Your radiators heat the house at …".
A room's load: the heat loss calculation or the estimate
The module takes each room's load from one of three places, in this order:
- "Typed load" - a value you type on the room. It comes first.
- The heat loss calculation. When you bring the rooms in with "Take rooms and loads from Heat loss", every room has its load from the heat loss calculation to EN 12831-1 - worked out from its building elements, windows, ventilation and temperature. When the project uses the heat loss calculation, a room that is not in it gets no estimate: the module does not mix two methods.
- The floor-area estimate. Without a heat loss calculation the module estimates the whole house's heat loss from the heated floor area, the building insulation, the design outdoor temperature and the room temperature, and shares it out over the rooms. The screen and the report say beside it: "An estimate from the floor area, not a calculation to EN 12831-1."
The estimate shows the direction - for example that the house needs a higher temperature than you want. To judge one room, and for the swap list, calculate the heat loss. How to do that is in the heat loss calculation guide.
Good to know
- The module calculates the radiators' output whatever the installation. The pipe network (the Network step) calculates two-pipe systems only, but you can check the radiators in any house.
- The output is calculated by the algorithm, not by Algo AI. Algo can only enter radiators from a photo or a design - see A radiator from a photo.
- The result is a radiator check, not an installation design.
A HeatAlgo report follows EN 12831-1 and EN 1264, not ACCA Manual J, and is not accepted for permits or rebates.