Cooling Only
Computer Room Unit
The design is peak air and peak cooling capacity.
A separate computer room unit, including air handler and cooling coil, is assumed for each room. Each unit is located on the ROA deck and draws return air from a common return air plenum. The design cooling supply air temperature is determined from user input and cannot be overridden by outside air reset schedules. The fans are constant volume while the coils are cycled to meet the load.
System Simulation
The computer room system operates in a manner similar to the single zone (SZ) system except that it will control the room humidity between the design room relative humidity and the humidification minimum relative humidity. The system will dehumidify and supply air if the average room relative humidity is above the design room relative humidity. The system will humidify the supply air if the room relative humidity is below the humidification minimum relative humidity setpoint.
When the room drift temperature rises above the room cooling thermostat, the cooling coil is energized (at a constant cooling supply air temperature) for a percentage of the hour that it takes to bring the room temperature down to the cooling thermostat temperature. If further dehumidification is needed, the cooling coil is energized for a longer percentage of the hour. For the portion of the hour that the cooling coil is de-energized, the supply air will remain at the return/outside air dry bulb temperature (plus supply fan heat). If the humidistat detects that the average room relative humidity exiting through the room return air grilles falls below the relative humidity minimum setpoint, the supply air is humidified before being admitted to the space.