Trane RT-PRC031-EN manual Controls Variable Air Volume VAV Only

Controls

Variable Air Volume (VAV) Only

Figure 11. IntelliPak™ II Control Panel

Bypass control is offered to provide full nominal airflow in the event of drive failure.

Supply Air Static Pressure Limit

The opening of VAV terminals, and the amount of supply air provided by the inlet guide vanes, or variable frequency drive are coordinated during start up and transition to/from Occupied/Unoccupied modes to prevent over pressurization of the supply air ductwork.

However, if for any reason the supply air pressure exceeds the user- defined supply air static pressure limit that was set at the Human Interface Panel, the supply fan/VFD is shut down and the inlet guide vanes

VAV Units Only

Note: When noted in this sequence “Human Interface Panel,” the reference is to both the unit mounted and remote mounted Human Interface Panel. All setpoint adjustments can be accomplished at the unit or Remote Human Interface Panel.

When in any position other than full open, the vanes pre-spin intake air in the same direction as supply fan rotation. As the vanes approach the full-closed position, the amount of “spin” induced by the vanes increases at the same time that intake airflow and fan horsepower diminish. The inlet guide vanes will close when the supply fan is shut down, except during night setback.

(if included) are closed.

The unit is then allowed to restart three times. If the over pressurization condition occurs on the third time, the unit is shut down and a manual reset diagnostic is set and displayed at the Human Interface Panel and BAS/Network.

Supply Air Temperature Controls

Supply Air Pressure Control

Inlet Guide Vanes Control

Inlet guide vanes are driven by a modulating 0-10 vdc signal from the Rooftop Module (RTM). A pressure transducer measures duct static pressure, and the inlet guide vanes are modulated to maintain the supply air static pressure within an adjustable user-defined range.

The range is determined by the supply air pressure setpoint and supply air pressure deadband, which are set through the Human Interface Panel or BAS/Network.

Inlet guide vane assemblies installed on the supply fan inlets regulate fan capacity and limit horsepower at lower system air requirements.

Variable Frequency Drive (VFD) Control

Variable frequency drives are driven by a modulating 0-10 vdc signal from the Rooftop Module (RTM). A pressure transducer measures duct static pressure, and the VFD is modulated to maintain the supply air static pressure within an adjustable user-defined range.

The range is determined by the supply air pressure setpoint and supply air pressure deadband, which are set through the Human Interface Panel or BAS/Network.

Variable frequency drives provide supply fan motor speed modulation. The drive will accelerate or decelerate as required to maintain the supply static pressure setpoint. When subjected to high ambient return conditions the VFD will reduce its output frequency to maintain operation.

Cooling/Economizer

During Occupied cooling mode of operation, the economizer (if available) and cooling are used to control the supply air temperature. The supply air temperature setpoint and deadband are user-defined at the Human Interface Panel.

The supply air temperature setpoint may be user-defined from the BAS/ Network. If the conditions of the outside air is appropriate to use “free cooling,” the economizer will be used first to attempt to satisfy the supply air setpoint; then if required the hydronic valve will be modulated to maintain supply air temperature setpoint.

On units with economizer, a call for cooling will modulate the fresh air dampers open. The rate of economizer modulation is based on deviation of the supply air

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