TESTING METHODS AND EQUIPMENT

TESTING METHODS AND EQUIPMENT There are two main methods of testing. The pressurization subtraction method utilizes a pressurization unit (i.e. a high-powered fan set up in a doorway and connected to pressure gauges) to pressurize first the entire space that is heated and/or cooled and then the same space with the duct system blocked off. This method is less accurate than the duct testing method. The duct testing method uses a calibrated fan that gently pressurizes the ducts and measures the airflow through the ducts to indicate total leakage. The duct tester consists of a portable fan with calibrated digital pressure gauges that is connected at the blower compartment of the air handler, or attached to the main return grill. All of the duct registers and grills are temporarily sealed, and the duct tester fan is turned on to pressurize the system. The fan pressure is read from the gauges and converted to an equivalent duct leakage rate in cubic feet per minute (cfm). If the amount of air loss falls outside acceptable limits, sealing will be required to correct the condition. This method of testing is preferred, because it measures low airflow accurately, and simulates what takes place under normal operating conditions.