What are the three main types of dampers?

Air Dampers: A Comprehensive Guide

An air damper is a device that uses valves or plates to control the flow of air within various systems, including ducts, chimneys, VAV boxes, and air-handling units. They are essential for airflow management and can also serve as protective measures against smoke and fire. Dampers are especially useful in stopping airflow into unoccupied or unused rooms, thereby conserving energy.

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Air dampers are intricate systems with numerous moving parts. Their key components include blades that adjust to manage airflow, along with frames, linkages, axles, bearings, seals, blade pins, actuating motors, flanging, jackshafts, and sleeves, among other parts.

Types of Air Dampers

Air dampers can be categorized into parallel blade and opposed blade dampers based on their construction. Each configuration offers distinct performance features for varying applications.

Parallel Blade Dampers

In parallel blade dampers, blades move in the same direction and are parallel to each other. This type is typically employed for open-closed operations. They adjust airflow in the first 20-30% of their movement from fully open to closed, making them ideal for redirecting airflow rather than modulating it.

These dampers are generally used in scenarios where they contribute significantly to the overall system pressure loss. However, they should be avoided upstream of critical components due to their tendency to produce uneven airflow.

Opposed Blade Dampers

Opposed blade dampers feature blades that rotate in opposite directions, effectively modulating airflow. They are suitable for systems requiring precise airflow control but can also function in on-off settings.

Common applications for opposed blade dampers include:

1. Systems where the damper does not significantly impact overall system pressure loss.
2. Systems that require even airflow downstream from the damper.
3. Ducted terminals.

Classification of Dampers by Control Method and Application

Air dampers can also be classified by their control method—automatic or manual—and their intended applications:

• Automatic dampers function similarly to automatic control valves.
• Manual dampers are adjusted manually based on the required airflow.

Dampers can serve various applications, including:

• Balancing dampers (volume dampers)
• Face and bypass dampers
• Fire dampers
• Smoke dampers
• Combined fire and smoke dampers
• Gravity dampers (backdraft or barometric)
• Mixing dampers
• Multi-zone dampers
• Round dampers
• VAV boxes (variable-air-volume)

Dampers are not only crucial for airflow management but also play vital roles in safety and fire protection applications.

Why Are Air Dampers Important?

Air dampers are key components in MEP engineering design, ensuring code compliance and energy efficiency by minimizing heat exchange when closed. In NYC, air dampers are subject to the following regulations:

1. National Fire Protection Association (NFPA) standards:
1. NFPA 90A: Standard for the Installation of Air-Conditioning and Ventilating Systems
2. NFPA 92A: Standard for Smoke-Control Systems Utilizing Barriers and Pressure Differences
3. NFPA 101: Life Safety Code
2. Underwriters Laboratories (UL) standards:
1. UL 555: Standard for Fire Dampers
2. UL 555S: Standard for Smoke Dampers
3. UL 555C: Standard for Ceiling Dampers
3. NYC Building Code
4. NYC Mechanical Code

Air dampers must comply with these codes in specific locations, such as stair enclosures, elevator shafts, common corridors, mechanical rooms, fire-rated walls, exterior building walls, shaft enclosures, horizontal assemblies, and duct and transfer openings.

Air Dampers in Fire Protection Applications

For fire protection, three main types of dampers are typically used: fire dampers, smoke dampers, and combined fire/smoke dampers. Let's explore each type and their specific applications.

Fire Dampers

Fire dampers automatically shut off airflow through ducts, preventing the passage of flames. These dampers are installed where ducts cross fire-rated assemblies or walls, and are available in both curtain and multi-blade types.

A fire damper generally includes these components:

1. Sleeve
2. Curtain blade
3. Break-away joints
4. Fusible link
5. Access door for inspection

All fire dampers are installed in the open position with a fusible link. When the temperature exceeds a set limit, the fusible link melts, closing the damper either by gravity or a spring mechanism. Fire dampers need to pass rigorous tests to ensure functionality.

Fire damper selection depends on fire resistance rating, temperature, and operation range. For less than 3-hour ratings, 1.5-hour fire dampers are used. For 3-hour or more ratings, 3-hour fire dampers are used.

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Conclusion

Air dampers have a diverse array of applications, from airflow control in regular operations to serving as critical barriers during emergencies. Compliance with local codes is essential, so partnering with qualified HVAC professionals is highly recommended. Ensure that your mechanical installations are compliant and energy-efficient to achieve optimal performance and safety.

Make sure your mechanical installations meet the necessary codes and are energy-efficient, with a 50% faster turnaround. Contact Nearby EngineersNew York Engineers by email (info@ny-engineers.com) or phone at (786) 788-0295212-575-5300 for more details.