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"). Various techniques can be used to protect these pumps from corrosion and particles. Zone dampers as used in home HVAC systems are usually electrically powered. Jeff Sines, a technical support team member at Engineered Software Inc., has almost 30 years of plant operations, process engineering, training and software engineering experience. Once the valve position of 100 percent and Cv value are entered, the system simulation software can estimate the remaining control valve data to fit the selected characteristic curve. On a wood-burning stove or similar device, it is usually a handle on the vent duct as in an air conditioning system. 1979 - © Copyright Cahaba Media Group, Inc. All Rights Reserved. Replace as required. 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. 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. Airflow Status Exhaust N.C. Mixed Air Dampers N.O. Some damper manufacturers provide performance curves for their products. Fire dampers are fitted where ductwork passes through fire compartment walls and fire curtains as part of a fire control strategy. The physical size of such solenoid valves have come down very considerably over the years. However, zone dampers that are of the "Normally Open" type are fail-safe, in that they will fail to the open condition.
Space temperature settings to be reset to 55°F winter and 85°F summer. This column describes how to model a damper in a system simulation software tool as a control valve with an approximated flow coefficient (Cv) profile. - Heating coil may be after the Removal of electrical power re-opens the damper. Observe damper motors and actuators through an operating cycle to check for defects or binding. A damper controls air flow throughout a duct system to evenly distribute air or gas. Missed your issue of Pumps & Systems because you are not at work? The first step is converting a set of data points (velocity and pressure drop) for the fully open position to a Cv value. Supply and return ducts need dampers to avoid pressurization of portions of the building. 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. Check pins, straps, bushings (bearings) for wear, rust or corrosion. Outside air damper to close. 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. 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. How to model a damper in a system simulation software tool as a control valve with an approximated flow coefficient profile. Multiple zones can be implemented using either multiple, individually controlled furnaces/air handlers or a single furnace/air handler and multiple zone dampers. W = mass flow rate (lb/hr) 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. All mounting bolts must be securely fastened. No inherent redundancy for the furnace. A damper specification datasheet is used as an example in this column. It operates by changing the size and shape of its flow path, so its flow capacity (or conversely, resistance) changes with position. 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. 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. Air handling units, which usually have the acronym of A.H.U are found in Each approach has advantages and disadvantages.
Linkages from actuators should be adjusted to insure blades of damper fully open or close within the stroke or travel of the actuator arm. Check blade edge and side seals. The piping geometry factor (Fp) is assumed to be 1.0 to evaluate the performance of the damper without attached reducers or other fittings. Like the second style of electrical zone damper, these dampers may allow adjustment of the "closed" position. Some manufacturer curves may be in other units such as cubic feet per minute (cfm). Caulking, where used to make damper frames tight to structure, should be checked and repaired as needed. In normal circumstances, these dampers are held open by means of fusible links. 3. Pneumatic actuation is preferred for these dampers. N.C. Outside Note: Coil arrangement may differ: - Preheat coil may be in the outside air duct before the mixed air sensor. Some damper manufacturers provide performance curves for their products. Subscribe. Its operation can be manual or automatic. The system simulation software needs the flow coefficient (Cv or Kv) at different throttling percentages in order to model the damper as a control valve. This event is caused by shutting off pipes quickly. The damper may be accessible only by reaching up into the fireplace by hand or with a woodpoker, or sometimes by a lever or knob that sticks down or out. We are a wholesale distributor and do not sell directly to the general public. Zone dampers are not 100% reliable. 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. 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. Damaged blades should be replaced. 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). should be removed especially around operating parts. In large commercial installations, vacuum or compressed air may be used instead. 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. A damper specification datasheet is used as an example in this column. These dampers also may allow adjustment of the "closed" position so that they only obstruct, for example, 75% of the air flow when closed. 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. A system with zone dampers is dependent upon a single furnace. Setting up the AHU. dP = pressure drop (psi) Set the outside-air damper to the selected minimum position. Furnaces cost much more than zone dampers, Power consumption. For electrical zone dampers, there are two principal designs. 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. This allows the zone dampers to be directly controlled by low-voltage thermostats and wired with low-voltage wiring. This month, he is a guest columnist in Hardee’s place. 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%. An expansion factor (Y) value of 1.0 is estimated in order to determine the Cv without considering the effect of gas expansion. 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. When installing automation systems, it’s important to make sure the existing dampers function properly when your computer sends a signal. In order to improve efficiency and occupant comfort, HVAC systems are commonly divided up into multiple zones. 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. Most AHU control damper actuators include a spring return so that upon loss of power or loss of a control signal the dampers return to their default positions. The equation from the Crane Technical Paper TP-410 to be used to obtain the Cv values is shown as Equation 1. Media related to Air dampers at Wikimedia Commons, This article is about the architectural element. 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. He served as an electrician in the U.S. Navy nuclear power program and earned a Bachelor of Science in mechanical engineering from the University of Texas. Its operation can be manual or automatic. To read more Pump System Improvement columns. Highly sophisticated systems may use some form of building automation such as BACnet or LonWorks to control the zone dampers. Cv = W63.3FPYxP'1ρ1−−−−−√Cv = W63.3FPYxP1'ρ1, Where: 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.
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