The constant flow heated floor keeps flow rate constant via a local circulation pump and varies the water temperature that is sent to the floor. This is accomplished with a mixing valve that is controlled by a sensor. The constant flow heated floor type has a built-in local secondary loop, which re-circulates flow coming out of the system and mixes this with flow from the loop to arrive at the desired inlet temperature to the floor (note that this heated floor model has the temperature sensor after the local secondary pump to ensure proper inlet temperature to the floor). The local loop also contains a pump which is assumed to be upstream of the component and after the mixing valve. So, the local loop can have some recirculation. The flow from the main loop may also bypass the component if more than enough flow is available and the main loop is also a constant flow system.
This is a read-only label that is automatically generated by the software and which incorporates the name of the zone in which the heated floor is located.
There are 3 ways to define the heating capacity of the unit as selected from the following list of options:
This autosizable field defines the convective electric nominal heating capacity (in W or Btu/h). It is only available when the Heating design capacity method is set to 1-Design capacity.
Enter the heating capacity per unit floor area (in W/m2 or W/ft2) of the unit. This data is only available when the Heating design capacity method is 2-Capacity per floor area.
The program calculates the heating capacity from floor area of the zone served by the unit and the heating capacity per unit floor area value specified here.
Enter the heating capacity as a fraction of the autosized heating capacity for convective electric baseboard unit. This data is only available when the Heating design capacity method is 3-Fraction of autosized capacity. EnergyPlus calculates the heating capacity from the design autosized heating capacity and this fraction. The default value is 1.0.
There are two types of heated floor available:
This is the inside diameter of the tubes through which water is circulated (in m or in). The inside diameter is used to determine the convective heat transfer from the water to the inside surface of the hydronic tubing.
This is the total length of embedded pipe (in m or ft). The length of the tube is used to determine the effectiveness of heat transfer from the fluid being circulated through the tubes and the tube/surface. Longer tubing lengths result in more heat that will be transferred to/from the radiant surface to the circulating fluid.
Note: With the constant flow heated floor, this length is not autosizable.
This input allows you to choose between modelling each surface in the radiant system as a single hydronic circuit or to allow the program to divide the surface into multiple parallel hydronic circuits based on the Circuit length (below). The corresponding options are:
It is recommended that 2-Calculate from circuit length be chosen for new models. The default is 1-One per surface for backward compatibility with older versions of DesignBuilder.
The length (in m or ft) of each parallel hydronic circuit in a surface. This data is only used when the Number of circuits (above) is set to 2-Calculate from circuit length. The default is 106.7 meters (350 feet), which is the maximum circuit length allowed in Title 24.
This is the maximum flow rate of water through the heated floor (in m3/sec or gal/min). This flow rate is held constant by the local component pump, but you have the option of varying this flow rate via a schedule (see Pump Flow Rate Schedule). The constant flow system will accept this flow rate and control the inlet temperature based on the control and water temperature schedules defined below.
This schedule modifies the maximum flow rate of water through the heated floor (in m3/s only). Note that the values for this schedule must be between zero and one.
This is the pump rated head (Pa or ftH20).
This is the pump rated power consumption (W).
This is the pump efficiency in decimal form (0 = 0%, 1 = 100%).
This is the fraction of the pump power lost to the fluid.
This option is only available when using the 2-Detailed HVAC Detailed HVAC Activity data
Along with setpoint (control) and water schedules, this setting allows you to specify how the heated floor is to be controlled. The temperature denoted in the setpoint schedule can refer to one of five different temperatures: the zone mean air temperature, the zone mean radiant temperature, the zone operative temperature, the outdoor dry-bulb temperature, or the outdoor wet-bulb temperature. The choice of temperature is controlled by the temperature control type. The user must select from the following options:
Operative temperature for heated floor controls is the average of Mean Air Temperature and Mean Radiant Temperature. See the control temperature schedule settings below for more information.
This schedule specifies the high water temperature (in °C only) for the temperature control of the constant flow heated floor. Water and control temperatures for heating work together to provide a linear function that determines the water temperature sent to the heated floor. The current control temperature (see Temperature Control Type above) is compared to the high and low control temperatures at the current time. If the control temperature is above the high temperature, then the system will be turned off and the water mass flow rate will be zero. If the control temperature is below the low temperature, then the inlet water temperature is set to the high water temperature. If the control temperature is between the high and low value, then the inlet water temperature is linearly interpolated between the low and high water temperature values.
This schedule specifies the low water temperature (in °C only) for the temperature control of the constant flow heated floor. For more information on its interpretation, Heating high water temperature schedule above.
This schedule specifies the high control temperature (in °C only) for the temperature control of a constant flow heated floor. For more information on its interpretation, see Heating high water temperature schedule above.
This schedule specifies the low control temperature (in °C only) for the temperature control of a constant flow heated floor. For more information on its interpretation, see Heating high water temperature schedule above.
This is the schedule that denotes whether the component can run during a given timestep. A schedule value greater than 0 (usually 1 is used) indicates that the unit is available and can be on during the timestep. A value less than or equal to 0 (usually 0 is used) denotes that the unit is not available and must be off for the timestep.