A
damper is a valve or plate that stops or regulates the flow of air inside a
ductDucts are used in heating, ventilation, and air conditioning to deliver and remove air. These needed airflows include, for example, supply air, return air, and exhaust air. Ducts also deliver, most commonly as part of the supply air, ventilation air...
,
chimneyA chimney is a structure for venting hot flue gases or smoke from a boiler, stove, furnace or fireplace to the outside atmosphere. Chimneys are typically vertical, or as near as possible to vertical, to ensure that the gases flow smoothly, drawing air into the combustion in what is known as the...
,
VAV boxVariable air volume is a technique for controlling the capacity of a heating, ventilating, and/or air-conditioning system. The simplest VAV system incorporates one supply duct that, when in cooling mode, distributes approximately supply air...
,
air handlerAn air handler, or air handling unit , is a device used to condition and circulate air as part of a heating, ventilating, and air-conditioning system. Usually, an air handler is a large metal box containing a blower, heating and/or cooling elements, filter racks or chambers, sound attenuators, and...
, or other air handling equipment. A damper may be used to cut off central
air conditioningAn air conditioner is a home appliance, system, or mechanism designed to dehumidify and extract heat from an area, or provide heat to an area. The cooling is done using a simple refrigeration cycle...
(heating or cooling) to an unused room, or to regulate it for room-by-room
temperatureIn physics, temperature is a physical property of a system that underlies the common notions of hot and cold; something that feels hotter generally has the higher temperature. Temperature is one of the principal parameters of thermodynamics...
and climate control. Its operation can be manual or automatic. Manual dampers are turned by a handle on the outside of a duct. Automatic dampers are used to regulate airflow constantly and are operated by
electricAn electric motor uses electrical energy to produce mechanical energy, usually through the interaction of magnetic fields and current-carrying conductors. The reverse process, producing electrical energy from mechanical energy, is accomplished by a generator or dynamo. Traction motors used on...
or
pneumaticA pneumatic motor is a machine which converts energy of compressed air into mechanical work. In industrial applications linear motion can come from either a diaphragm or piston actuator. As for rotary motion, either a vane type air motor or piston air motor is used. Rotary motion vane type air...
motors, in turn controlled by a
thermostatA thermostat is a device for regulating the temperature of a system so that the system's temperature is maintained near a desired setpoint temperature. The name is derived from the Greek words thermos "hot" and statos "a standing"...
or
building automationBuilding automation describes the functionality provided by the control system of a building. A building automation system is an example of a distributed control system...
system.
In a chimney
flueA flue is a duct, pipe, or chimney for conveying exhaust gases from a fireplace, furnace, water heater, boiler, or generator to the outdoors. In the U.S.A., for water heaters and modern furnaces they are also known as 'vents' and for boilers as 'breeching'. They usually operate by buoyancy, also...
, a damper closes off the flue to keep the
weatherWeather is a set of all the phenomena occurring in a given atmosphere at a given time. Weather phenomena lie in the troposphere. Weather refers, generally, to day-to-day temperature and precipitation activity, whereas climate is the term for the average atmospheric conditions over longer periods...
(and
birdBirds are winged, bipedal, endothermic , vertebrate animals that lay eggs. There are around 10,000 living species, making them the most numerous tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Birds range in size from the Bee Hummingbird to the ...
s and other animals) out and warm or cool air in.
A
damper is a valve or plate that stops or regulates the flow of air inside a
ductDucts are used in heating, ventilation, and air conditioning to deliver and remove air. These needed airflows include, for example, supply air, return air, and exhaust air. Ducts also deliver, most commonly as part of the supply air, ventilation air...
,
chimneyA chimney is a structure for venting hot flue gases or smoke from a boiler, stove, furnace or fireplace to the outside atmosphere. Chimneys are typically vertical, or as near as possible to vertical, to ensure that the gases flow smoothly, drawing air into the combustion in what is known as the...
,
VAV boxVariable air volume is a technique for controlling the capacity of a heating, ventilating, and/or air-conditioning system. The simplest VAV system incorporates one supply duct that, when in cooling mode, distributes approximately supply air...
,
air handlerAn air handler, or air handling unit , is a device used to condition and circulate air as part of a heating, ventilating, and air-conditioning system. Usually, an air handler is a large metal box containing a blower, heating and/or cooling elements, filter racks or chambers, sound attenuators, and...
, or other air handling equipment. A damper may be used to cut off central
air conditioningAn air conditioner is a home appliance, system, or mechanism designed to dehumidify and extract heat from an area, or provide heat to an area. The cooling is done using a simple refrigeration cycle...
(heating or cooling) to an unused room, or to regulate it for room-by-room
temperatureIn physics, temperature is a physical property of a system that underlies the common notions of hot and cold; something that feels hotter generally has the higher temperature. Temperature is one of the principal parameters of thermodynamics...
and climate control. Its operation can be manual or automatic. Manual dampers are turned by a handle on the outside of a duct. Automatic dampers are used to regulate airflow constantly and are operated by
electricAn electric motor uses electrical energy to produce mechanical energy, usually through the interaction of magnetic fields and current-carrying conductors. The reverse process, producing electrical energy from mechanical energy, is accomplished by a generator or dynamo. Traction motors used on...
or
pneumaticA pneumatic motor is a machine which converts energy of compressed air into mechanical work. In industrial applications linear motion can come from either a diaphragm or piston actuator. As for rotary motion, either a vane type air motor or piston air motor is used. Rotary motion vane type air...
motors, in turn controlled by a
thermostatA thermostat is a device for regulating the temperature of a system so that the system's temperature is maintained near a desired setpoint temperature. The name is derived from the Greek words thermos "hot" and statos "a standing"...
or
building automationBuilding automation describes the functionality provided by the control system of a building. A building automation system is an example of a distributed control system...
system.
In a chimney
flueA flue is a duct, pipe, or chimney for conveying exhaust gases from a fireplace, furnace, water heater, boiler, or generator to the outdoors. In the U.S.A., for water heaters and modern furnaces they are also known as 'vents' and for boilers as 'breeching'. They usually operate by buoyancy, also...
, a damper closes off the flue to keep the
weatherWeather is a set of all the phenomena occurring in a given atmosphere at a given time. Weather phenomena lie in the troposphere. Weather refers, generally, to day-to-day temperature and precipitation activity, whereas climate is the term for the average atmospheric conditions over longer periods...
(and
birdBirds are winged, bipedal, endothermic , vertebrate animals that lay eggs. There are around 10,000 living species, making them the most numerous tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Birds range in size from the Bee Hummingbird to the ...
s and other animals) out and warm or cool air in. This is usually done in the summer, but also sometimes in the winter between uses. In some cases, the damper may also be partly closed to help control the rate of combustion. The damper may be accessible only by reaching up into the
fireplaceA fireplace is an architectural structure to contain a fire for heating and, especially historically, for cooking. A fire is contained in a firebox or firepit; a chimney or other flue directs gas and particulate exhaust to escape. Fireplaces are a central household feature, as the flames and...
by hand or with a woodpoker, or sometimes by a lever or knob that sticks down or out. On a wood
burningCombustion or burning is a complex sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat or both heat and light in the form of either a glow or flames, appearance of light flickering.Direct combustion by atmospheric oxygen is a reaction...
stoveA stove is an enclosed heated space. The term is commonly taken to mean an enclosed space in which fuel is burned to provide heating, either to heat the space in which the stove is situated or to heat the stove itself, and items placed on it...
or similar device, it is usually a handle on the
ventVent may refer to:*Vent , a slit up the back of a jacket or coat*Vent , a valve fitted to the top of a submarine's ballast tanks*Vent , a 2001 album by Caliban...
duct as in an air conditioning system. Forgetting to open a damper before beginning a
fireFire is the rapid oxidation of a combustible material releasing heat, light, and various reaction products such as carbon dioxide and water. If hot enough, the gases may become ionized to produce plasma. Depending on the substances alight, and any impurities outside, the color of the flame and the...
can cause serious
smokeThis article is about the substance. For other uses, see Smoke .Smoke is the collection of airborne solid and liquid particulates and gases emitted when a material undergoes combustion or pyrolysis, together with the quantity of air that is entrained or otherwise mixed into the mass...
damage to the interior of a home, if not a house fire.
Automated zone dampers
A zone damper (also known as a
Volume Control Damper or
VCD) is a specific type of damper used to control the flow of air in an
HVACHVAC is an acronym that stands for the closely related functions of "Heating, Ventilating, and Air Conditioning"-the technology of indoor environmental comfort...
heating or cooling system. In order to improve efficiency and occupant comfort, HVAC systems are commonly divided up into multiple zones. For example, in a house, the main floor may be served by one heating zone while the upstairs bedrooms are served by another. In this way, the heat can be directed principally to the main floor during the day and principally to the bedrooms at night, allowing the unoccupied areas to cool down.
Zone dampers as used in home HVAC systems are usually electrically powered. In large commercial installations,
vacuumIn everyday usage, vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. The word comes from the Latin term for "empty," but in reality, no volume of space can ever be perfectly empty...
or
compressed airCompressed air is air which is kept under a certain pressure, usually greater than that of the atmosphere. In Europe 10 % of all electricity used by industry is used to produce compressed air...
may be used instead. In either case, the motor is usually connected to the damper via a mechanical coupling.
For electrical zone dampers, there are two principal designs.
In one design, the motor is often a small
shaded-pole synchronous motorShaded-pole synchronous motors are a class of AC motor.Like a shaded pole induction motor, they use field coils with additional copper shading coils to produce a weakly rotating magnetic field. But unlike a shaded pole induction motor , the synchronous version of this motor uses a magnetized rotor...
combined with a rotary switch that can disconnect the motor at either of the two stopping points ("damper open" or "damper closed"). In this way, applying power to the "open damper" terminal causes the motor to run until the damper is open while applying power at the "close damper" terminal causes the motor to run until the damper is closed. The motor is commonly powered from the same 24
voltThe volt is the SI derived unit of electromotive force, commonly called "voltage". It is also the unit for the related but slightly different quantity electric potential difference...
acIn alternating current the movement of electric charge periodically reverses direction. An electric charge would for instance move forward, then backward, then forward, then backward, over and over again...
power source that is used for the rest of the control system. This allows the zone dampers to be directly controlled by low-voltage
thermostatA thermostat is a device for regulating the temperature of a system so that the system's temperature is maintained near a desired setpoint temperature. The name is derived from the Greek words thermos "hot" and statos "a standing"...
s and wired with low-voltage wiring. Because simultaneous closure of all dampers might harm the furnace or air handler, this style of damper is often designed to only obstruct a portion of the air duct, for example, 75%.
Another style of electrically powered damper uses a
springA spring is an elastic object used to store mechanical energy. Springs are usually made out of hardened steel. Small springs can be wound from pre-hardened stock, while larger ones are made from annealed steel and hardened after fabrication...
-return mechanism and a shaded-pole synchronous motor. In this case, the damper is normally opened by the force of the spring but can be closed by the force of the motor. Removal of electrical power re-opens the damper. This style of damper is advantageous because it is "fail safe"; if the control to the damper fails, the damper opens and allows air to flow. However, in most applications "fail safe" indicates the damper will close upon loss of power thus preventing the spread of smoke and fire to other areas. These dampers also may allow adjustment of the "closed" position so that they only obstruct, for example, 75% of the air flow when closed.
For vacuum- or pneumatically-operated zone dampers, the thermostat usually switches the pressure or vacuum on or off, causing a
spring-loadedA spring is an elastic object used to store mechanical energy. Springs are usually made out of hardened steel. Small springs can be wound from pre-hardened stock, while larger ones are made from annealed steel and hardened after fabrication...
rubber diaphragm to move and actuate the damper. As with the second style of electrical zone dampers, these dampers automatically return to the default position without the application of any power, and the default position is usually "open", allowing air to flow. Like the second style of electrical zone damper, these dampers may allow adjustment of the "closed" position.
Highly sophisticated systems may use some form of
building automationBuilding automation describes the functionality provided by the control system of a building. A building automation system is an example of a distributed control system...
such as
BACnetBACnet is a Data Communications Protocol for Building Automation and Control Networks. It is an ASHRAE, ANSI, and ISO standard protocol.- Definition :...
or
LonWorksLonWorks is a networking platform specifically created to address the needs of control applications. The platform is built on a protocol created by Echelon Corporation for networking devices over media such as twisted pair, powerlines, fiber optics, and RF...
to control the zone dampers. The dampers may also support positions other than fully open or fully closed and are usually capable of reporting their current position and, often, the temperature and volume of the air flowing past the smart damper.
Regardless of the style of damper employed, the systems are often designed so that when no thermostat is calling for air, all dampers in the system are opened. This allows air to continue to flow while the heat exchanger in a furnace cools down after a heating period completes.
Comparison to multiple furnaces/air handlers
Multiple zones can be implemented using either multiple, individually-controlled furnaces/air handlers or a single furnace/air handler and multiple zone dampers. Each approach has advantages and disadvantages.
Multiple furnaces/air handlers
Advantages:
- Simple mechanical and control design ("SPST thermostats")
- Redundancy: If one zone furnace fails, the others can remain working
Disadvantages:
- Cost. Furnaces cost much more than zone dampers
- Power consumption. Operating furnaces draw power whereas a zone damper only draws power while in motion from one state to the other (or, in some cases, a very small amount of power while holding closed).
Zone dampers
Advantages:
Disadvantages:
- Zone dampers are not 100% reliable. The motor-to-open/motor-to-closed style of electrically operated zone dampers aren't "fail safe" (that is, they do not fail to the open condition). However, zone dampers that are of the "Normally Open" type are fail-safe, in that they will fail to the open condition.
- No inherent redundancy for the furnace. A system with zone dampers is dependent upon a single furnace. If it fails, the system becomes completely inoperable.
- The system can be harder to design, requiring both "SPDT" thermostats (or relay
A relay is an electrically operated switch. Electric current through the coil of the relay creates a magnetic field which attracts a lever and changes the switch contacts...
s) and the ability of the system to withstand the fault condition whereby all zone dampers are closed simultaneously.
Fire dampers
Fire dampers are fitted where ductwork passes through fire compartment walls / fire curtains as part of a fire control strategy. In normal circumstances, these dampers are held open by means of fusible links. When subjected to heat, these links fracture and allow the damper to close under the influence of the integral closing spring. The links are attached to the damper such that the dampers can be released manually for testing purposes. The damper is provided with an access door in the adjacent ductwork for the purpose of inspection and resetting in the event of closure.
See also
- Zone valve
A zone valve is a specific type of valve used to control the flow of water or steam in a hydronic heating or cooling system.In the interest of improving efficiency and occupant comfort, such systems are commonly divided up into multiple zones. For example, in a house, the main floor may be served...
- Variable air volume
Variable air volume is a technique for controlling the capacity of a heating, ventilating, and/or air-conditioning system. The simplest VAV system incorporates one supply duct that, when in cooling mode, distributes approximately supply air...
(VAV)
External links