For vacuum-operated or pneumatically operated zone dampers, the thermostat usually switches the pressure or vacuum on or off, causing a spring-loaded rubber diaphragm to move and actuate the damper. In large commercial installations, vacuum or compressed air may be used instead. For other uses, see, Comparison to multiple furnaces/air handlers, Learn how and when to remove this template message, Heating, ventilation, and air conditioning, High efficiency glandless circulating pump,, Heating, ventilating, and air conditioning, Articles needing additional references from September 2014, All articles needing additional references, Creative Commons Attribution-ShareAlike License, Simple mechanical and control design ("SPST, Redundancy: If one zone furnace fails, the others can remain working, Cost. © Copyright Cahaba Media Group, Inc. All Rights Reserved.

Temporarily set up the unit for 100-percent-outside-air operation: Shut off the return fan, close the return damper, and open the outside-air damper. When installing automation systems, it’s important to make sure the existing dampers function properly when your computer sends a signal. The motor is commonly powered from the same 24 volt AC power source that is used for the rest of the control system. Some damper manufacturers provide performance curves for their products. More accurate data should be obtained from the manufacturer or field measurements if possible. Learn the 6 Benefits of IoT Condition-Based Maintenance in this white paper.

Because this is an estimated value based on values taken from a curve, different points on the curve can be used to determine the Cv and an average can be defined. This performance curve has velocity units in feet per minute and pressure drop in inches of water gauge. Manual dampers are turned by a handle on the outside of a duct. The piping geometry factor (Fp) is assumed to be 1.0 to evaluate the performance of the damper without attached reducers or other fittings. In some cases, the damper may also be partly closed to help control the rate of combustion. Cv = W63.3FPYxP'1ρ1−−−−−√Cv = W63.3FPYxP1'ρ1, Where: A damper may be used to cut off central air conditioning (heating or cooling) to an unused room, or to regulate it for room-by-room temperature and climate control. 3. A system with zone dampers is dependent upon a single furnace. A nuclear plant was having mechanical seal failures too often. A damper specification datasheet is used as an example in this column. In this example, a butterfly, center shaft body style was used with a trim type of aligned 60 degrees and equal percentage characteristic curve. 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%. Forgetting to open a damper before beginning a fire can cause serious smoke damage to the interior of a home, if not a house fire.

Learn steps for acquiring, installing and specifications for a vacuum system. New US residential building codes require permanent access to dampers through ceiling access panels. Another style of electrically powered damper uses a spring-return mechanism and a shaded-pole synchronous motor.

By entering the damper diameter and reading one value of dP at a select fluid velocity from the performance curve, the Cv can be determined. AHU Applications Application Note 5 Mixed Air Single Path Applications Schematic Figure 2 is a schematic of a mixed air single path application. Damaged blades should be replaced. 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. Linkages from actuators should be adjusted to insure blades of damper fully open or close within the stroke or travel of the actuator arm. Like the second style of electrical zone damper, these dampers may allow adjustment of the "closed" position. In normal circumstances, these dampers are held open by means of fusible links. The damper is provided with an access door in the adjacent ductworks for the purpose of inspection and resetting in the event of closure. © 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. Airflow Status Exhaust N.C. Mixed Air Dampers N.O. Once the Cv is found, a control valve data estimator in a piping design software can be used to estimate a Cv profile for the damper. x = pressure drop ratio dP/P'1 For example, the 36-inch damper has a pressure drop of 0.018 in water column (wc) at a velocity of 2,000 feet per minute (ft/min) air velocity. An expansion factor (Y) value of 1.0 is estimated in order to determine the Cv without considering the effect of gas expansion. Some damper manufacturers provide performance curves for their products. P'1 = absolute inlet pressure (psia) Leaking or sticking dampers can ruin your system balance and energy efficiency. Automatic dampers are used to regulate airflow constantly and are operated by electric or pneumatic motors, in turn controlled by a thermostat or building automation system. 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 HVAC heating or cooling system. Most styles of motor-to-open/motor-to-closed electrically operated zone dampers aren't "fail safe" (that is, they do not fail to the open condition). Outside air damper to close. The next step is reading data from the performance curve and converting the units to accommodate the equation. Check pins, straps, bushings (bearings) for wear, rust or corrosion. Positioning the outside-air damper. It is easier to provide zone-classified solenoid valves for pneumatic actuation, as compared to electrical actuation.

Hear how AODD pumps can solve common rotating pump problems. At 100 percent open, the damper has a calculated Cv of 143,649 (which corresponds to a resistance coefficient of about 0.07). Y = expansion factor (between 0.667 at choked flow to 1.0 for no expansion) The links are attached to the damper such that the dampers can be released manually for testing purposes. 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. In a chimney flue, a damper closes off the flue to keep the weather (and birds and other animals) out and warm or cool air in. Check blade edge and side seals. W = mass flow rate (lb/hr) A damper controls air flow throughout a duct system to evenly distribute air or gas. This month, he is a guest columnist in Hardee’s place. Fire dampers are fitted where ductwork passes through fire compartment walls and fire curtains as part of a fire control strategy. 2.

Lubricate all mechanisms and moving parts. On a wood-burning stove or similar device, it is usually a handle on the vent duct as in an air conditioning system. A damper is used extensively in the heating, ventilation and air conditioning (HVAC) industry as well as other industries that move air or compressible gases for their processes. Setting up the AHU. Zone dampers as used in home HVAC systems are usually electrically powered. Missed your issue of Pumps & Systems because you are not at work? FP = piping geometry factor accounts for fittings attached to the valve We are a wholesale distributor and do not sell directly to the general public. Click here or call 1-800-227-9800. This allows air to continue to flow while the heat exchanger in a furnace cools down after a heating period completes. should be removed especially around operating parts. Pneumatic actuation is preferred for these dampers. Subscribe. In one design, the motor is often a small shaded-pole synchronous motor combined with a rotary switch that can disconnect the motor at either of the two stopping points ("damper open" or "damper closed").

If humidity sensors are not used to control humidity, ? A damper specification datasheet is used as an example in this column.

The outside-air damper is normally closed and the return-air damper is normally open. A damper is a valve or plate that stops or regulates the flow of air inside a duct, chimney, VAV box, air handler, or other air-handling equipment. 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). The equation from the Crane Technical Paper TP-410 to be used to obtain the Cv values is shown as Equation 1. Air handling units, which usually have the acronym of A.H.U are found in Get our latest news & updates:

Its operation can be manual or automatic. These dampers also may allow adjustment of the "closed" position so that they only obstruct, for example, 75% of the air flow when closed. In this case, the damper is normally opened by the force of the spring but can be closed by the force of the motor. No inherent redundancy for the furnace. Dirt, soot lint, etc. 1979 - It will also enter an FL and xT profile based on typical butterfly valves shown in the International Electrotechnical Commission (IEC) and International Society of Automation (ISA) standards for sizing control valves. Maximizing ROI on Pressure Boosting Investments, Eliminate mechanical seal failure headaches, downtime, and cost. Linkages from actuators should be adjusted to insure blades of damper fully open or close within the stroke or travel of the actuator arm. Observe damper motors and actuators through an operating cycle to check for defects or binding. Caulking, where used to make damper frames tight to structure, should be checked and repaired as needed. Room occupancy sensor, along with the “Time of Day” program will cause the AHU's and terminal units to go to unoccupied mode settings when called for by the schedule program. Highly sophisticated systems may use some form of building automation such as BACnet or LonWorks to control the zone dampers. 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. Blades should be checked in closed position to be sure all close tightly. Removal of electrical power re-opens the damper. An example performance curve graph of pressure vs. air velocity is shown on the next page for fully open dampers of 16 inches, 24 inches and 36 inches. 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. In order to improve efficiency and occupant comfort, HVAC systems are commonly divided up into multiple zones.


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