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PLC-5000 Site Controller, LD-2000 and LD-2000 PLC 5.0 Description of the Vaporless Automatic Line Leak Detector The official descriptions of the Vaporless equipment and test methods are found in Attachment A of this report on the appropriate EPA forms. The Vaporless PLC-5000 Site Controller with the 98 LD-2000 PLC combines an electronic line leak detector and a mechanical line leak detector to conduct 3 gal/h, 0.2 gal/h, and 0.1 gal/h leak detection testing. Additional features include interfacing of dispenser pan sensors, and interstitial sensors, power-line communication, PC/power- line interface, bidirectional serial data port, and true plug-and-play component installation and upgrades. The system consists of a site controller central control node, leak detector node, monitor node, and mechanical line leak detector. Power lines are used as the communication pathways. Communication can be transmitted on lines over 5,000 feet, and can be installed to bridge phases on multi phase powered sites. Using LonWorks® communication protocol, the system can distinguish separate pieces of equipment and include or ignore information exchanged between system components. The data transceivers communicate at a bit rate of 5 kbps and after error correction overhead provide a net bit rate of 4 kbps. Exchange of information regarding status and control of equipment is facilitated by application software resident in each system control element, referred to as a "node." However, under no circumstance can the electronic system disable the mechanical portion of the leak detection system. Site Controller Central Control Node The Central Control Node (CCN) monitors for product dispensing requests: monitors for Leak Detector Node activity and controls the operation of up to four product turbines; monitors for activity at up to 16 Dispenser Monitor Nodes; calculates, stores, prints, and transfers results of electronic line tests; and in the event of a detected 3 gal/h leak, the CCN will shutdown the associated turbine and issue an appropriate alarm. The CCN automatically performs monthly and annual precision line leak tests. Tests may also be manually initiated. Additional features of the CCN include the following: • Stores up to 99 error messages in its nonvolatile memory. • Error messages may be printed on the optional printer. • Information exchange through a bi-directional RS-232 serial port. • System status viewed on a 2-line by 24-character backlit LCD display. • Results from 0.2 and 0.1 gal/h tests are time/date stamped (TDS) and recorded in a log which cannot be cleared. • A test port is provided for field testing of software and hardware. Page 6