Chinese (Simplified)EnglishFrenchGermanHindiItalianJapaneseKoreanPortugueseRussianSpanish

Preferred Utilities

Preferred Utilities engineers and fabricates fuel oil handling systems for diesel generators and dual-fuel fired boilers for mission critical facilities such as data centers, hospitals, and emergency response facilities. Our engineers specialize in mission critical fuel oil system design so they are current with the latest industry practices and fire protection codes. In addition, Preferred Utilities offers a wide variety of fuel oil system components designed to meet the unique requirements of our fuel oil customers. Preferred Utilities' industrial factory is located in Danbury, CT

High Liquid Level Alarm Switch

The Model HLS-LF High Level Switch is used on fuel oil storage tanks to provide a simple and reliable means of sounding an alarm or providing an electrical interlock as the liquid level approaches tank capacity.



The Model HLS Tank Fil-A-Larm Switch is used on light fuel oil storage tanks to reliably activate an overfill warning signal. This alerts the transfer operator to stop filling the tank. Federal codes for overfi ll prevention may be satisfied by an overfill alarm that sounds when the tank contents reach 90% of the tank capacity or one minute prior to overflow if the rate of fill is constant. Refer to Model HLS-LF for heavier No. 4, No. 5, and No. 6 fuel oil grades.


  • Provides Simple And Reliable Means Of Sounding An Alarm
  • SPDT Snap Action Micro Switch
  • Actuated By A Stainless Steel Lever Float



Mounting: 4″ NPT Half Coupling

Fluid Temperature: 275° F Maximum

Fluid Specific Gravity: 0.7 Minimum

Fluid Pressure: 100 Psig Maximum

Electrical: SPDT, 10 Amps / 120VAC, 5 Amps Resistive 30 VDC

Switch Trip: Specified By Customer, Maximum Length 25 Inches

Electrical Housing: Cast Aluminum, Weatherproof, Explosion Proof

Wetted Parts: Stainless Steel, Brass, and Cast Iron

UL listed: Class I Groups C & D, Class II Groups E, F, & G



The switch shall be designed to sound an alarm or provide an electrical interlock when the tank level reaches the specified length below the mounting threads. Unit is to include a stainless steel lever-operated float and shall be suitable for 100 psig and 275° F. Unit shall be constructed of stainless steel, brass and cast iron wetted parts, and shall be designed for threading into a 4″ NPT half coupling at the tank top. The switch shall be magnetically linked to the float mechanism and fully isolated from the tank contents.  Electrical connections shall be contained in a weather and explosion proof head assembly. The unit shall be listed by Underwriters Laboratories.  The High Liquid Level Switch shall be provided and shall be a Preferred Utilities Manufacturing Corporation, Danbury, CT, Model HLS-LF.