HVAC Damper Types

HVAC Damper Types

Manual Damper HVAC Volume Damper Ductwork Fitting.

HVAC Damper Types - Most of us, when we think of an air damper, think of rushing to a freshly lit fireplace to flip the soot covered handle that opens the chimney as the room fills with smoke. The HVAC damper is a simple enough concept, direct or redirect airflow in your air conditioning or exhaust system according to your specific requirements. So why are there so many different styles? They range from $5 to $500, so what’s the difference, and which one do you need?

HVAC Damper Types

Damper, I barely know her?

Basic Manual Volume Damper

These are the most typical of the HVAC ductwork dampers. The purpose of these duct fittings is to adjust the air velocity for specific branches of duct. For example, if you have way too much air coming out of your master bedroom, you can close the damper to that room, either partially or all the way, and the air will be redirected to other parts of the system. Many novices buy these thinking that they can use them to completely shut off a branch of duct, this is not the case.

These volume dampers, even when all the way closed, still allow some air through. You will notice that even when closed there is a small gap all the way around the blade. These are not for closing off a duct completely, they are simply for “balancing” the airflow in a system to the desired levels. Always make sure you tighten the wing nuts and hardware as tightly as possible so that the blade is locked in place, and so you don’t get an annoying rattling or buzzing sound. Lower quality fittings will often buzz and rattle, so make sure you’re not cutting corners on quality!


Manual Volume Damper W/Standoff Handle | HVAC Damper Types

The manual volume damper with standoff handle is required when the sheet metal duct has an external insulation. The standoff handle allows the damper blade to be adjusted without being hindered by the insulation. But, these are also a great option for dust collection systems, paint spray booths, smokers, or any application that requires frequent air flow adjustments. At The Sheet Metal Kid we make them with a slightly thicker gauge of metal, and the handle allows for convenient access and maximum adjustability.

Backdraft Dampers (aka Butterfly Damper) | HVAC Damper Types

The purpose of the backdraft damper is exactly what the name suggests, it blocks air from reversing and blowing back into the vent in the wrong direction. For example, you may put these on a fresh air vent that goes out an exterior wall so that the indoor air can go out, but the outdoor air cannot get back into the conditioned space. There are different designs, but most commonly the back draft damper has a hinge in the center of the balancing blade that only collapses in one direction.

Butterfly Backdraft Damper

Barometric Pressure Relief Fitting - Bypass Damper

HVAC Duct Fire Smoke Damper

HVAC Duct Fittings Control Damper Zone

Barometric “Bypass” Damper | HVAC Damper Types

These are rather elegantly designed little fittings with no electricity required, and minimal moving parts. They have a handle similar to the “standoff” style, but there is also a weight that can be slid up or down. These dampers open and allow air to escape when a certain barometric pressure is reached, thus equalizing the air pressure on either side of the metal fitting according to how you have adjusted the weight.

Control Dampers (aka Zone Damper) | HVAC Damper Types

The control damper has an electric motor that can open or close the damper when the temperature control system commands. These are often used for optimizing the air conditioning system by adding zones. Zones are designated in a building according to many criteria; occupancy, solar heat gain, fresh air requirements, etc. You may use a zone damper along with an occupancy sensor so that when a space is occupied the zone damper opens, and when it is not occupied, the zone damper is closed, so that air is directed to other zones in the building that are in use.

Fire Damper or Fire/Smoke Damper | HVAC Damper Types

Fire dampers and Fire/Smoke dampers part of the building’s life safety system. They usually require an auxiliary power source that will not be interrupted if the building catches fire. Building codes differ on exactly when these are required, but it’s usually when duct is penetrating a partition of a certain fire rating. The fire damper automatically closes ventilation when it gets the signal that there is a fire. This closes the air duct so that the fire isn’t fed by the ac system, and to slow the fire from spreading to other areas. Fire/smoke dampers are essentially the same thing, except that they also have smoke sensor, in addition to the fire sensor.

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Duct Detectors Smoke Detection – NFPA 90A Code Requirements

What you will learn from Duct Detectors Smoke Detection - NFPA 90A Code Requirements article:

  1. Preface for the NFPA 90A requirements for duct detectors in air conditioning and heating equipment.
  2. The question: Where do you install duct detectors in duct work?
  3. detailed answer to satisfy requirements
  4. exclusions and exceptions to the requirement
  5. references for further information about HVAC equipment and fire safety
  6. Finally, additional related information about fire and smoke dampers regarding HVAC

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Duct Work and High Ceilings | HVAC Duct Work Systems

Duct Work and High Ceilings

Duct Work and High Ceilings | HVAC Duct Work Systems

Duct Work and High Ceilings – I did not see any reference to my question and would appreciate a response as soon as possible, as due to medical situation, have to make a decision soon. We own an OLD house with 13′ ceilings in a large part of the home and 11″ ceilings in the LV/DR and BR. We are oscillating on where to place the ducts….Floor or ceiling. It appears to be counterproductive to me to put the duct work in the ceiling since it will have so far to go. We are looking for the most cost-effective, not upfront cost but operating cost, solution. In addition, we are considering DF heat pumps. The house will need 2 or 3 to be zoned correctly. Please let me know about the duct placement and thank you for your help? (more…)

Air Conditioner Ductwork Leaks | Leaky Duct Work

Air Conditioner Ductwork Leaks | Leaky Duct Work - A good consideration when replacing the air conditioning system is the duct work.

Air Conditioner Ductwork Leaks

Red Arrow Shows a Duct Work Leak

Duct work seems to be the most ignored part of an HVAC system. However, it is a very important consideration in this age of new technology and higher energy efficient equipment being developed and manufactured. You can have the most energy efficient engine but if its in an old 60 or 70’s model car your efficiency is going to suffer. The same is true with HVAC systems. (more…)

Magnehelic Duct Pressure Sensor

Magnehelic Duct Pressure Sensor - Magnehelic Duct Static PressureMagnehelic Duct Pressure Sensor - The magnehelic measures duct pressure inside of ductwork. It is important, for many reasons, to know the pressure inside of duct work. This magnehelic measures the supply side pressure of the blower inside the air handler. The static pressure in this system is actually controlled by a static pressure transducer which is directly hooked up to a DDC controller that controls a variable frequency drive based on static pressure. The static pressure transducer is a solid state magnehelic and works in much the same way a magnehelic works except the transducer is digital and sends out a signal that registers the pressure it is reading. The magnehelic pictured is simply for visual display and reading the static pressure inside the air handler. It does not send out any signals. (more…)

Duct Systems and Bad Ductwork

Duct Systems and Bad DuctworkBad Ductwork - Ductwork is necessary to deliver the air throughout the HVAC system. It is important that the system has integrity with no leaks. Duct work is made of different materials. Duct systems also have different construction methods which hold the ductwork together.

Pictured above is an old ductwork system (which needs to be replaced) made of duct board, which is a rigid fiberglass board, and flex duct work. The duct board is cut to size from the duct work sizing requirements for tonnage and taped together with special duct tape. For the branches coming off the duct board trunk, metal collars are inserted into holes cut to size in the duct board. Flex ductwork is attached to the metal collars for the branch ductwork. (more…)

HVAC Duct Systems

HVAC Duct Systems - Round Hard Duct WorkHVAC Duct Systems - Ductwork systems channel the air to the spaces where it is needed from the air handler. HVAC duct systems also pulls the air from the space and channels it back to the air handler where it needs to be conditioned. In some commercial applications the area above the ceiling is considered the return duct. All the return air is channeled back to the air handler through the plenum where it is conditioned in the air handler. Part of the conditioning process is the air being passed through a filter and then an exchanger like a coil or heat exchanger. (more…)

Duct Work | Heating and Cooling Mechanical

Duct WorkMost air conditioning and heating systems require some form of duct work. Duct work channels or directs the air to places in the dwelling where the conditioned air is needed. There are many types of ductwork available. Often times the ductwork can make a big difference in your utility bills. For that reason, it is important that the ductwork is installed correctly by qualified installation technicians. (more…)

Ductwork Integrity & Insulation | HVAC Airflow

Ductwork Integrity & Insulation | HVAC Airflow 

Ductwork Integrity & InsulationSo you are having a new HVAC system installed and you selected a system that is high efficiency and you want to get the most out of it. Have you looked at or has the HVAC contractor looked at the duct work and determined if it is good enough for the high efficiency system. A good HVAC contractor would look at the ductwork to make sure it is adequate and sized properly for the new system. This is often done as the HVAC contractor wants to ensure that the new system is properly matched to the HVAC ductwork lest the system not work as it should. Beyond that the most overlooked part of the ductwork is the ductwork integrity.

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