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HVAC BALANCE Constant Air Volume - Call us at (800) 217-8437There is a misconception that variable air volume systems are self-balancing. Our air balance services correct this problem. We ensure the building will be clean and free of dirt and dust. We test and record leaving air temperatures - D.B. heating a cooling coils. A multi-zone unit uses a single fan to produce both cold and hot air. Cooling and heating coils are both used to produce either cold air, hot air, or a mixture of both when the space temperature has been satisfied. Actuators are used to move mixing dampers in the discharge of the unit to achieve the correct position to meet space temperature requirements. The unit can maintain a designed discharge air temperature on both the cooling and heating sides of the unit by modulating the chilled and hot water valves. The unit is made up of 2 or more zones serving various spaces. Each zone duct will have a manual balancing damper that MUST be installed to balance out the airflow on each zone duct. Design airflow should be set first by pitot tube traverse through the zones before any grille balancing is started. 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. Part-load performance of equipment is a critical consideration for HVAC sizing. Most heating and cooling equipment only operate at their rated, peak efficiency when fully loaded (that is, working near their maximum output). However, HVAC systems are sized to meet design heating and cooling conditions that historically occur only 1% to 2.5% of the time. Thus, HVAC systems are intentionally oversized at least 97.5% to 99% of the time. In addition, most equipment is further oversized to handle pick-up loads and to provide a factor of safety. Therefore, systems almost never operate at full load. In fact, most systems operate at 50% or less of their capacity. Most green builders already know their duct basics: (1) Duct leaks are very common; in many homes, duct leaks are responsible for significant energy losses, (2) For ducts located in an unconditioned attic, any leaks in the supply system tend to depressurize a house, while return-system leaks tend to pressurize a house. Either condition can cause problems, (3) Duct leaks outside of a home thermal envelope waste more energy than duct leaks inside a home thermal envelope, (3) Even if ducts are located inside of a home thermal envelope, duct leaks can still connect to the outdoors, and (4) It is much easier to seal duct seams during new construction than in an existing house. Mechanical ventilation is the use of mechanical air handling systems commonly referred to as heating, ventilation, and air conditioning (HVAC) systems to ventilate buildings. Most commercial buildings use mechanical ventilation, which is more controllable and responsive than natural ventilation in providing adequate indoor air quality. However, mechanical ventilation also can exacerbate infiltration and ex filtration, which can compromise indoor air quality. Research clearly shows that when a fire occurs in a multi-compartmented building, the smoke from the fire is a far greater hazard to the occupants than the fire itself. Smoke can kill by asphyxiation or poisoning well before the temperature of the fire or smoke causes injury. Smoke also obscures vision, preventing occupants from finding safe escape routes and hindering the fire brigade search and rescue operation. 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). |
