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HVAC BALANCE Multi-Zone Systems - Call us at (800) 217-8437Variable Air Volume (VAV) systems are so varied and some are so complex that one set of balancing specifications cannot be written to cover all situations. We consider all situations and have experienced most of them at some point over our 20 year history. We test and record motor full load amperage. We test and adjust systems for design CFM recirculated air. In a rectangle duct traverse it is important to get an equal number of readings to cover the whole cross section of the duct. Drilling the correct number of holes and spacing the holes correctly is the most important part. The first step is finding the area of the duct in square feet. A pressure pan is a diagnostic tool consisting of a metal pan (similar to a cake pan) connected by a tube to a manometer (that is, a pressure gauge). The device is used to temporarily cover a forced-air register to measure the pressure exerted on the pan by a blower door. To conduct a pressure-pan test, you need a pressure pan and a blower door. Here are the basic steps: (1) A blower door is used to depressurize the home to 50 Pascals, (2) The air handler fan is turned off, (3) The tester then blocks each register (one at a time) with the pressure pan and records the reading of the pressure-pan manometer. (The manometer shows the pressure created by air leaking into the duct system.) Typical readings of the duct system pressure (with respect to the house pressure) range from 1 Pascal to 45 Pascals, and (4) The higher the reading, the leakier the duct run. The varying exposures of the rooms of a school or other building similarly occupied require that more heat shall be supplied to some than to others. Rooms that are on the south side of the building and exposed to the sun may perhaps be kept perfectly comfortable with a supply of heat that will maintain a temperature of only 50 or 60 degrees in rooms on the opposite side of the building which are exposed to high winds and shut off from the warmth of the sun. With a constant and equal air supply to each room it is evident that the temperature must be directly proportional to the cooling surfaces and exposure, and that no building of this character can be properly heated and ventilated if the temperature cannot be varied without affecting the air supply. There are two methods of overcoming this difficulty: The older arrangement consists in heating the air by means of a primary coil at or near the fan to about 60 degrees, or to the minimum temperature required within the building. From the coil it passes to the bases of the various flues and is there still further heated as required, by secondary or supplementary heaters placed at the base of each flue. A Variable Air Volume (VAV) box, is a part of an air conditioning system. It is located inside the duct work. It is designed to control the air flow to a specific area, called a zone. The VAV regulates the volume of the air to the zone by opening or closing the damper, thus controlling the amount of conditioned air directed to the zone. Each zone in a building has a thermostat which controls the VAV, telling it when to open or shut the damper based upon the needs of the zone. In many buildings, the air distribution system also includes a return air system so that conditioned supply air is returned to the AHU (return air) where it is mixed with supply air, re-filtered, re-conditioned, and re-circulated throughout the building. This is usually accomplished by drawing air from the occupied space and returning it to the AHU by: (1) ducted returns, wherein air is collected from each room or zone using return air devices in the ceiling or walls that are directly connected by duct work to the air-handling unit; or (2) plenum returns, wherein air is collected from several rooms or zones through return air devices that empty into the negatively pressurized ceiling plenum (the space between the drop ceiling and the real ceiling); the air is then returned to the air-handling unit by duct work or structural conduits. HVAC BALANCE offers test and balance services for the testing, adjusting and balancing of residential, commercial and industrial Heating, Air Conditioning and Ventilation systems. This service is a through checkout of all your equipment, duct work, control systems and all integral components that ensure that your HVAC systems are operating at peak operating conditions to save you energy, money and the environment. Heating can be accomplished by heating the air within a space (e.g. supply air systems, perimeter fin-tube radiators), or by heating the occupants directly by radiation (e.g. floor/ceiling/wall radiation or radiant panels). |
