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A simplified Veeder-Root Vacuum Sensor system installation in an STP sump is shown in Figure 1. Seal off To console *I-- Dual weatherproof junction boxes w/cord grip wiring entries containing epoxy sealed connections Double wall sump vacuum fitting` 'If multiple ports are provided in the sump wall, install vacuum fitting in lowest one. Double wall tank Wiring from sensor in tank interstice connects to vac sensor in j box STP L Tank interstitial sensor vacuum fitting Four Vac Sensor Housing Assembly bracketed to riser / IIiIN!IIIF: Barbed fitting in siphon port for vacuum source Product line vacuum fitting Vapor return line vacuum fitting vacsensor vacseninslall.eps Figure 1. Four Vacuum Sensor Assembly w/Tank Interstitial Sensor Installation Example A functional diagram of a Vac Sensor system is shown in Figure 2. The TLS Console turns the pump on, opens the vacuum control valve (in Vac Sensor), and then monitors the pressure sensor (in Vac Sensor). Under normal operation, when the vacuum reaches either 1 psi above the entered relief valve pressure (relief valve installed), or -8 psi (no relief valve installed), unless the rate of evacuation decreases to less than 0.1 gpm, the console closes the vacuum control valve and turns off the pump. Thereafter, the console continues to monitor the pressure sensor for signs of a decrease in vacuum (leak) and the liquid float for the presence of a liquid in the vacuum line. In the event of a decrease in vacuum the console turns on the pump in an attempt to restore the vacuum. Small leaks will be maintained by these periodic evacuations. If the system calculated leak rate exceeds approximately 25 gph a Vac Warning will be posted. The console also monitors the liquid float in the Vac Float module or tank interstice and will post a High Liquid Alarm if enough liquid accumulates in the vac line liquid reservoir to lift the float.