ST-15 Overfill Prevention Control Unit

Single Point Overfill Prevention Control Unit

  • Features two-wire optic or thermistor sensing
  • Mounted at a loading rack or fill station for connection to a single compartment tank vehicle
  • Features Dynacheck® circuitry for automatic and continuous self-checking of all system components

  • Will not permit loading under any fault or wet sensor conditions
  • Signals for automatic shut-off of product flow within a half-second of detecting an overfill condition
  • Ideal overfill prevention for single compartment refuelers, tank cars, or hazardous liquids tank trailers; the ST-15 System is an excellent choice for rail car loading with portable cane sensors
  • The only monitor that supports Scully three-wire, high-temperature sensors, allowing for a sensing of a wide range of petroleum products and chemicals
  • Easy connection to vehicles through the Scully junction box and plug and cable units
  • 30 years of proven, dependable performance
  • For additional ground verification options, consult Scully for information on the Groundhog Self-Proving Grounding System
  • For top-loading portable sensor options, see product page for Portable Liquid Level Sensors


Part NumberDescription
07528ST-15-115-EL Single Point Controller with Explosion-proof Housing & Indicator Lamps, 115VAC
07677ST-15-115-ELK Single Point Controller with Explosion-proof Housing, Indicator Lamps, Lockable Bypass Switch, 115VAC
07640ST-15-240-EL Single Point Controller with Explosion-proof Housing, Indicator Lamps, 240VAC
07547ST-15-240-ELK Single Point Controller with Explosion-proof Housing, Indicator Lamps, Lockable Bypass Switch, 240VAC


Part NumberDescription
08756120 VAC- Control circuit module only, ST-15-120H
08656240 VAC- Control circuit module only, ST-15-240H

FM & CSA Approved Versions of:

Thermistor SensorsSP-BL, SP-BLU, SP-BLH two-wire Optic Sensors SP-TO, SP-TOM, SP-IO, SP-IR, SP-TO(SS), SP-TO(SS)HP
Enclosures:Explosion-proof, weathertight. Corrosion inhibiting epoxy paint optional
Indicator Lamps:Red = Power On/Non-Permit Green = Permit
Approvals:XP-AIS / I / 1 / CD / T6 Ta = -40°C to 60°C; Entity – 61654; XP-AIS/ I / 1 / IIB/ T6 Ta = -40°C to 60°C; Entity 61654 Class I Zone 1 Group IIB
Turn on response time:6 – 30 seconds (typical) for thermistors. Two-wire optics turn on instantly.
Shutdown Response Time:0.5 seconds maximum
Power Requirements:105 – 130 VAC, 50-60 Hz, 20 watts maximum, 210 – 250 VAC nominal, 50-60 Hz, 20 Watts maximum
Connections:Provided by internal terminal strips
Output Control:One normally open volt free contact, rated 250 VAC, 5A resistive, energized when the sensor is dry.
Output Control Fuse:Internal 5 Amperes.
Size:Refer to Diagram for EL & ELK models.
Weight:28 lbs. (12.7 kg) EL & ELK Units

NOTE: The Scully ST-15 is an intrinsically safe system. For maximum safety, it should be used only in conjunction with sensors manufactured by Scully not to jeopardize the conditions of the approvals.

Scully Signal