Generally, a constant volume with reheat system provides cooling by means of a cooling coil located in the air supply sub-loop AHU that supplies cooling to the entire supply air volume. The cooling coil is controlled by a controller setpoint specified for the cooling coil. Zone control is accomplished by heating (reheating) the airflow into each zone as determined by the zone thermostat. Reheat can be supplied by an electric, gas or hot water coil that tries to meet the zone demand.
The unit contains a single heating coil which can be edited to change the type to 1-Water, 2-Electric or 3-Gas.
This is a read-only label that is automatically generated by the software and which incorporates the name of the zone in which the ADU is located.
The design maximum volume flow rate (in m3/sec) specified for the ADU. This field may be auto-sized.
This section is visible only if the heating coil sub-component of this ADU has Type 1-Water.
The maximum hot water volumetric flow rate (in m3/s) through the unit’s heating coil if a water coil has been selected. This value may be auto-sized.
The minimum hot water volumetric flow rate (in m3/s) through the unit’s heating coil if a water coil has been selected. This value may be auto-sized.
This is the schedule that determines whether or not the unit is available for each timestep of the simulation. A schedule value greater than 0 (usually 1 is used) indicates that the unit can be on during the timestep . A value less than or equal to 0 (usually 0 is used) denotes that the unit must be off for the timestep .
The coil is controlled by knowing the zone demand determined by the zone thermostat and setting the outlet conditions to meet this demand. For the electric and gas coils, this is set exactly since the coil model solution can be inverted. With the hot water coil that uses an effectiveness-NTU method, the solution cannot be inverted directly. Therefore, to determine the correct mass flow rate for the hot water the solution is solved for by iteration. The iterative solution uses an interval halving routine and needs a termination criterion that is set with the Convergence Tolerance parameter. This control offset is set to a decimal fraction of the zone demand as the criteria, i.e. 0.001. The default for the field is 0.001.