3.7.5.5 Four-Pipe Fan Coil Systems

Capacity Control Method

Applicability

Four-pipe fan coil systems

Definition

The control method for the fan coil unit at the zone. The following choices are available:

• Constant fan variable flow: The fan speed is held constant to produce a fixed airflow rate whenever the unit is scheduled on. The hot water or chilled flow rate is varied so that the unit output matches the zone heating or cooling requirement.
• Constant fan constant flow: The fan speed is held constant to produce a fixed flow rate whenever the unit is scheduled on. The chilled water and hot water flow rates are kept constant at full flow.
• Cycling fan: The fan speed is chosen so that the unit capacity is greater than or equal to the heating/cooling load and the fan is cycled to match unit output with the load.
• Variable fan constant flow: The water flow rate is at full flow and the fan speed varies to meet the load.
• Variable fan variable flow: Both air and water flow rates are varied to match the load.

Units

List (with choices above)

Input Restrictions

Not a user input – derived from building descriptors for fan control and chiller loop flow control

Baseline Building

Four pipe fan coil systems are applicable for proposed buildings with the system type defined in Table 72. The capacity control for the baseline building will be specified as “Constant Fan Constant Flow.”