American Aldes patent-pending Three Parallel Damper In-Line Zone Terminals (ZRT-3PDIL-HP) are designed to introduce flexibility and dynamic control to central supply or exhaust ventilation systems. Used in both large and small systems, the ZRT-3PDIL-HP regulates ventilation air without the need for individual fans or traditional VAV terminal units. Each ZRT-3PDIL-HP is a three-position, pressure-independent terminal with two control dampers to regulate multiple high-limit on-demand airflow controls and integral passive regulators for automatic air balancing of the minimum and maximum airflow setpoints. This unique combination provides flexible control schemes without the need for expensive pneumatic, electronic, or DDC control systems.

The ZRT-3PDIL-HP is primarily used for combination low-flow indoor air quality ventilation or make-up air, and two on-demand high-flow spot ventilation rates, for uses such as bathroom exhaust fans, using the same central exhaust or supply fan system. This is achieved by integrating a minimum High-Pressure Constant Airflow Regulator (CAR-II-HP) in the terminal end panel, and in-line with the branch duct. The maximum airflows are controlled by a series of 24 VAC or 120 VAC powered motorized damper(s) and a secondary CAR-II-HP airflow controller.

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

When other ZRT-3PDIL-HP are activated for on-demand control of high flow, the unpowered ZRT-3PDIL-HP will maintain the specified low-continuous rate through the pressure-independent CAR-II-HP minimum flow control. Opening the ZRT-3PDIL-HP’s control damper adds its calibrated airflow rates to the minimum setpoint, allowing for full maximum-boost ventilation.

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