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After the emergency timer elapses, the Fume Hood Controller will begin actively controlling the airflow, but at an increased setpoint. The Emergency Purge sequence is canceled by pressing the Emergency Purge button a second time. The ODP indicates an Emergency Purge sequence in three ways: • The red LED illuminates. • The horn sounds. • EMERGENCY PURGE and EEE display. Siemens Building Technologies, Inc. Applications The fume hood operator may silence the horn by pressing the Horn Silence button on the ODP without affecting the Emergency Purge sequence. In addition to the ODP indicators, the emergency alarm point will toggle to ON and will remain ON until the sequence is canceled. If the emergency alarm is alarmable in the field panel, the condition can be indicated at selected terminals if the APOGEE Automation System is set up for it. Emergency Purge Strategies The use of the Emergency Purge button is determined by the work practices established by the laboratory safety officer. As a general rule, there are two groups that should be aware of the use of the Emergency Purge button: the laboratory worker and the laboratory safety officer. Laboratory worker – In most cases, the laboratory worker uses the Emergency Purge button to increase the fume hood airflow to minimize a dangerous situation. The Emergency Purge button should not be used as a way to work around the established face velocity and minimum flow setpoints in an effort to make the fume hood "even safer". Laboratory safety officer – For the safety department personnel to use the Emergency Purge feature effectively, they must select the purge mode that best suits their needs. The selection may be based on knowledge of industrial hygiene, the chemicals used in the laboratory, the organization's emergency procedures, and the capacity of the central exhaust system. If the maximum purge mode is selected, the emergency timer and the emergency setpoint to their maximum values. If the controlled purge mode is selected, the emergency timer is set to 0. Select the value for the emergency setpoint to indicate how much you want the emergency airflow to increase over the normal airflow. For example, if your emergency procedures call for closing the fume hood and starting the emergency purge, decide how much airflow you want compared to the minimum airflow. If you want twice as much airflow, set the emergency setpoint to 200%; if you want a 50% increase, set the emergency setpoint to 150%. If you do not intend to have the laboratory worker close the fume hood, then select the face velocity you want the fume hood to control to in an emergency. Compare that value to the normal face velocity setpoint and calculate the emergency setpoint in percent. NOTE: During a controlled purge, the increased airflow called for in the controlled purge may exceed the range of the flow sensor. If so, the system cannot accurately regulate the airflow and the controller will open the exhaust flow control device 100%. If a sequence initially employing maximum purge with a switch to controlled purge is desired, set the emergency setpoint as described for the controlled purge. Select a value for the emergency timer to tell the system how long to leave the exhaust flow control device open before switching to controlled purge. Base this on the types of accidents anticipated, the reason you require a maximum purge, and the reason you want to switch it down to a controlled purge. Siemens Building Technologies, Inc. Fume Hood Controller Owner's Manual In addition to setting up the purge sequence to effectively handle the exhaust needs, decisions must be made on how to use the information available at the central reporting station. Consult your local Siemens Building Technologies, Inc. representative for more information on central reporting and trending of emergency purge information. Fail-safe Operation If the Fume Hood Controller or one of its accessories fails, then a failure mode sequence will be initiated. Fume Hood Controller If the Fume Hood Controller power fails, the exhaust flow control device will go to the full open position. Since there would be no power to the controller, no LEDs or display will be available on the ODP. NOTE: If the power fails to both the exhaust fan and the controller, there will be no indication except for the absence of the noise that the air makes during normal operation. ODP If the ODP fails, the controller will continue to control the fume hood face velocity. However, no display or audible alarming will be available. Differential Pressure Transmitter If the differential pressure transmitter fails, the controller will control the exhaust flow control device to the fully open position. The ODP will display FFF and GENERAL FAILURE. Electronic Actuator Assembly If the electronic actuator or interface board fails then alarms are displayed on the ODP indicating unsafe operating conditions. Pneumatic Actuator If the actuator fails due to a leak, then the exhau...