Overview

American Aldes patent-pending Parallel Damper In-line Zone Terminals (ZRT-PDIL) are designed to introduce flexibility and dynamic control to central supply or exhaust ventilation systems. Used in both large and small systems, the ZRT-PDIL regulates ventilation without the need for individual fans or traditional VAV terminal units. Each ZRT-PDIL is a two-position pressure-independent terminal with a control damper to regulate high limit on-demand airflow control and integral passive regulators for automatic air balancing of the minimum and maximum setpoints. This unique combination provides flexible control schemes without the need for expensive pneumatic, electronic, or DDC control systems.

The ZRT-PDIL is primarily used for combination low-flow indoor air quality ventilation or make-up air, and on-demand high-flow spot ventilation, such as bathroom exhaust fans, using the same central exhaust or supply fan system. This is achieved by integrating a CAR-II minimum airflow controller in the terminal end panel, and in-line with the branch duct. The maximum airflow is controlled by a series of 120V or 24V powered motorized damper(s) and a secondary CAR-II airflow controller.

With the maximum air motorized control damper completely closed, the factory-calibrated minimum CAR-II allows steady, low-continuous airflow control.

When other ZRT-PDIL terminals are activated for on-demand control of high flow, the unpowered ZRT-PDIL will maintain the specified low continuous rate through the CAR-II pressure-independent minimum flow control. Opening the ZRT-PDIL’s control damper adds its calibrated airflow rate to the minimum setpoint, allowing for full maximum-boost ventilation.

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