Pump up/Pump down controller


Feature Variable Liquid Level Differential
PLUS Single Point Pump Up/Pump Down Level Control

Component Recognized (E85349)

  • Four field replaceable liquid level differential bands are standard.
  • ΔH = 1.0″ ΔH = 2.0″ ΔH = 3.0″ ΔH = 5.0″
  • Interchangeable differential band modules allow 5 minute on site switching of differential from 1.0″ to 2.0″ to 3.0″ to 5.0″ in any sequence to satisfy variable operational requirements as they occur.
  • Large Differential provides immunity to nuisance switch tripping due to severe wave action and turbulence.
  • Large Differential also provides very low cost single point pump up/pump down level control.
  • Model L-21 is ideal for make-up water level control in cooling towers, plating and washing tanks, fish farms, fountains, and aquariums.
  • For use in contaminated fluids. However, we suggest appropriate analysis and testing in each situation.

L-21N Employs Noryl Polyphenylene Oxide (PPO) Engineering Plastic and 316 Stainless

Wetted Surfaces For:

  • Clean Water
  • Contaminated Groundwater
  • Filtered Sewage
  • Filtered Waste Water
  • Inorganic aqueous solutions and related liquids
  • Mild Acid/Bases
  • Sea Water

11 amp 120/240 VAC SPDT Switch allows direct control of 1/3 hp pumps, 1.2 kw heaters, motor contactors, solenoid valves, etc.

Intrinsically safe relay allows Model L-21 to be used in hazardous area.

Temperature to 200°F continuous at 75 psig

Pressures to 250 psig at 75°F

Maintenance and checkout is a snap for plant maintenance personnel using any standard multimeter.

Each unit comes with detailed Instruction Manual and Parts List.

Plastic test strips are available for testing in your particular “real world” chemical environment.

Extensive Chemical Corrosive List Available


L-21N Wetted Surfaces

  1. Noryl Polyphenylene Oxide (PPO) with 10% glass fiber.
  2. 316 Stainless hardware

Electrical Switch Characteristics

  • SPDT
  • UL and CSA listed
  • 11 A, 1/3 HP; 125/250 VAC
  • 1/2 A 125 VDC, 1/4 AMP 250 VDC
  • 4A 125 VAC (lamp load)

Nominal Working Pressure/Temperature

Tested to Failure at 800 psig at room temperature

Temperature °F 75° 100° 150° 200°
Pressure (psig) 250 200 150 75

Working Fluid Spec. Gravity: 0.7 Min.

Weight: 5 oz. (142 g)

Installation Dimensions

Liquid Level Differential Dimensions

Input Power Cable Interface Options


NOTE: Model L-21N employs magnetic coupling between float arm and switch body. Magnetic particles can accumulate on and around magnetic housing which may affect proper operation. Please conduct appropriate fluid magnetic particle evaluation and operational tests prior to and during installation and use.

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