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HVAC BALANCE Duct Leakage Systems - Call us at (800) 217-8437We ensure that floor covering activities are completed. We verify that all dampers are open. We test and record system static pressures, suction and discharge. The following are steps that should be taken when balancing a multi-zone unit: (1) Filters must be clean, (2) Check fan rotation, belt tension, and motor amp draw, (3) Check for installation of all zone dampers and to verify that they are in the full open position, (4) Run all zones to full cooling, (5) Verify that all ductwork has been sealed, (6) Leaving air temperatures should be taken on each zone in full cooling to make sure that there is no leakage coming through the hot deck dampers. Same should be done in full heating, (7) If unit has outside air set the damper to an estimated position. Recheck fresh air amount after unit airflow has been balanced, and (8) Condensate drain must be installed with vent in the correct location. Gravity dampers or an exhaust fan can be used to control building pressure. An engineer can subtract the amount of exhausts (such as toilet exhausts) from the minimum-outside-air quantity and estimate the extent to which the remaining outside air could pressurize the building. During commissioning, pressurization set points can be determined by taking building-pressure field measurements with known outside-air quantities. One drawback is that the method does not truly control minimum outside air. The method uses a surrogate, such as the supply-fan capacity signal, as an approximation of total supply airflow. The controls use the surrogate signal to open the outside-air damper further as the supply fan slows, maintaining a nearly constant minimum outside airflow rather than a constant percentage of supply airflow. Example Air Test and Balance Procedure: (1) List and identify size, type and manufacturer of all diffusers, grilles, registers and all tested equipment. Use equipment manufacturer ratings to make any required calculations, (2) Identify each grille, diffuser and register with a number that is referenced on an accompanying sketch, (3) If the system is variable air volume (VAV), adjust all the terminal unit flow rate regulators to the required minimum and maximum CFM while monitoring and recording duct static pressure. If the system is constant volume (CV), proceed to step #5, (4) Set enough VAVs to maximum CFM and minimum CFM to equal the rated cooling coil CFM, (5) Test and adjust system for design percentage of outside air, (6) Test and record motor load amperes, (7) Make pitot tube traverse of main supply ducts, where possible, to determine total supply CFM, (8) Test and adjust blower RPM as necessary to achieve design CFM, (9) If the system is constant volume, adjust all zones to proper design CFM, supply and re turn, (10) Test and adjust each diffuser, register and grille to within plus or minus 10% of design requirements. Care should be taken to minimize drafts whenever possible, (11) Test and record re-circulated air flow rate (CFM), (12) Test and record system static pressures, suction and discharge, (13) Temporarily set water flows and temperatures to design conditions for temperature tests, (14) Test and record entering air temperatures. (D.B. heating and cooling), (15) Test and record entering air temperatures. (W.B. cooling), (16) Test and record leaving air temperatures. (D.B. heating and cooling), (17) Test and record leaving air temperatures. (W.B. cooling), (18) List test data for all diffusers, grilles and registers, including design CFM and test resultant CFM after adjustment. When Direct Reading Flow Hoods cannot be used, applicable Ak factor, design velocity and test resultant velocity shall be shown, (19) Test and record required information pertaining to other equipment included in the HVAC contract such as electric duct heaters, exhaust fans, computer room units, (20) The Mechanical Contractor shall be responsible for making any changes in the pulleys, belts and dampers or adding dampers as recommended by the air balance agency to achieve correct air balance. Characteristics of a good duct system: (1) Has been designed to meet ACCA Manual D requirements with each duct carefully sized to provide the airflow needed to meet room-by-room heat loss and heat gain calculations, (2) Has been designed so that duct runs are as short and straight as possible, (3) Does not use building cavities (for example, panned joists or stud bays) as ducts, (4) Locates all ducts within the home thermal envelope, (5) Includes ducts or air paths that allow return air to flow back to the air handler from every room with a supply register, (6) Has all seams sealed with duct mastic and (6) Has been tested for duct leakage. Kitchen Hood Grease Duct Leakage Testing is performed as a service to provide proof that the grease duct systems installed on a kitchen hood system has no leaks. We use only professional calibrated equipment to perform these tests to ensure the validity of these tests. The use of high performance HVAC equipment can result in considerable energy, emissions, and cost savings (10%-40%). Whole building design coupled with an extended comfort zone can produce much greater savings (40%-70%). Extended comfort includes employing concepts such as providing warmer, but drier air using desiccant de-humidification in summer, or cooler air with warmer windows and warmer walls in winter. In addition, high-performance HVAC can provide increased user thermal comfort, and contribute to improved indoor environmental quality (IEQ). Safety factors for HVAC systems allow for uncertainties in the final design, construction and use of the building, but should be used reasonably. Greatly over-sized equipment operates less efficiently and costs more than properly sized equipment. For example, over-sized cooling systems may not dehumidify the air properly, resulting in cool but clammy spaces. It is unreasonable and expensive to assume a simultaneous worst-case scenario for all load components (occupancy, lighting, shading devices, weather) and then to apply the highest safety factors for sizing. |
