A popular home ventilation system consists of a central exhaust fan located in the attic or basement with ducts running to grilles in the kitchen and baths. The system has two advantages: First, you only need one fan. Second, there's less noise in the living area. But multipoint systems can be hard to balance, and if you boost the fan speed to expel odors from the bathroom, you also raise the ventilation rate in the kitchen. This pulls more cold air into the house, which increases heating costs.

To solve the problem, American Aldes has introduced a Constant Exhaust Grille with variable override. The grille contains a silicone rubber bulb that resembles an hourglass. The bulb is factory-calibrated so that when pressure in the duct increases the spring expands, blocking more of the duct area and maintaining a constant airflow. This simplifies balancing by letting you choose the grille that most closely matches the airflow required for a particular room. The basic CEG grille restricts the airflow to a preset amount. However, a unique variable flow model provides spot ventilation. The bulb is set in a plastic housing that's connected to a pull cord on the outside of the grille. Pulling the cord rotates the housing, exposing a larger free area to the duct. This lets you increase airflow through one grille without increasing fan speed or affecting other grilles in the system.

The CEG comes in 4-in. or 5-in. diameters. Airflows vary from 10 to 25 cfm, with overrides from 18 to 80 cfm. It's designed for use with Aldes' SPV 200 and 300, but can be used with any in-line fan having a flat fan curve. (A flat fan curve means it will maintain constant duct pressure regardless of the amount of air flowing through the registers. This lets you increase or decrease airflow at one grille without affecting the others.)

Contact: American Aldes