SECTION 2.0 2.1 LEAK ANALYSIS VIA A FLOW METER Looking for an air leak in a large building can be like looking for a needle in a haystack, if a logical approach is not employed. We suggest using the information provided by a flow meter in the main air supply line of the control system. When using the flow meter information, one can break the building down into three potential areas where the leaks may occur. (1) The exhaust fans. (2) The supply fan systems. (3) The thermostat loops associated with the main air distribution system. CHECKING FOR LEAKS AT THE EXHAUST FANS (1) Using walkie-talkies have one person at the flow meter and one person at the central control to stop and start the exhaust fans. (2) Note the airflow reading at the meter with all the exhaust fans turned off. Turn the exhaust fans on one at a time and note the air flow meter reading after each one has started. The person at the meter should notice an initial surge when an exhaust fan with pneumatic actuator starts, but the meter should settle to the same point of the fan not running, after the actuator has filled. (3) If the airflow reading is the same with the exhaust fans on or off, there is no leak associated with the exhaust fans; therefore, start with the supply fan air leak investigation. (4) If the air flow meter jumps up when an exhaust fan starts and remains up, you likely have a leak either on the line from the solenoid to the pneumatic actuator or the diaphragm in the actuator has a leak. (5) If the airflow meter jumps up when an exhaust fan is turned off, you likely have a leak in the solenoid air valve from the normally closed port to the normally open port and the solenoid should be replaced. 9-166
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