TLS-450 Setup and Operation Screens Manual
59
Threshold
The Threshold field lets you enter vapor levels to identify a leak or serious spillover and to trigger the
vapor alarm. Thresholds are in ohms and must be calculated for each vapor sensor according to the
procedure described below. Thresholds may be set to account for existing vapor levels as long as these
vapors do not exceed the limits explained below.
BEFORE YOU BEGIN
IMPORTANT! A vapor sensor must be operated only in wells where preliminary testing has determined
that the soil is not already contaminated beyond acceptable limits (as defined by applicable regulations)
or that contaminated soil has been remediated and is now clean. A vapor sensor should not be operated
in wells where preliminary testing indicates that the initial vapor sensor resistance exceeds 25k ohms.
Vapor sensors must have been installed in their wells at least 24 hours prior to calculating and entering
vapor alarm thresholds.
This system contains electrical voltages that can be lethal.
Electrical shock resulting in serious injury or death could result if incorrect service
procedures are used. When you perform the following procedure:
1.Read all instructions carefully
2.Turn Off power to the console.
DETERMINING THRESHOLD
1. Turn Off all AC power to the console.
2. Open the right-hand door of the console and determine the USM module to which the vapor
sensor is connected. The vapor sensor has a 3-wire cable with black "+" , green "-" and white "+"
colored wires. Every 3-wire sensor should connect to adjacent terminals on the USM module.
3. Find the module connections of the Vapor Sensor which is to be measured for a vapor threshold
value.
4. Measure the resistance across the "+" (black wire) and "-" (green wire) terminals using an
ohmmeter.
5. Multiply the measured resistance by 4 to determine the vapor threshold value that you should
enter.
6. Enter the calculated vapor threshold value.
Allowable selections: 1000 - 100,000 ohms
Default: 0
Category
Select the sensor's category (location) from the drop down list.
Allowable selections: Other Sensors, Annular Space, Dispenser Pan, Monitor Well, STP Sump,
Containment Sump
Default: Other Sensors
