Internal Liquid Level Switch
Model A

The Model A is an internal service, horizontally mounted liquid level switch.


Body: The threaded body is 316 Stainless Steel.
Float: A 2-1/2" round float is 316 Stainless Steel with an optional Copper Float.
Trim: The float rod and its related hardware are 300 series stainless steel.
Pressure: Maximum pressure is limited by the float used. Copper is 30 PSIG and Stainless is 500 PSIG.
Specific Gravity: The minimum standard specific gravity is 0.8.
Mounting: The connection is 2-1/2" NPT. The control must be installed through a half-coupling. A full coupling interferes with the operation of the float mechanism.
Insertion Length: The standard insertion is 8-1/2" as measured from the face of the control to the end of the float(s). Minimum insertion is 5-3/4". Custom insertion lengths are available. Please contact sales for more information.
Differential: With the standard insertion, the field adjustable differential is 1" to 6". For greater differential, additional insertion length is required. Approximately 1/8" of additional differential can be achieved for each 1" added insertion length. High level actuation will occur at approximately 3/4" above the centerline of the control. Differential adjustment changes the low level point only.
Switches: See Model V.
Switch Housing: A water-tight/dust-tight or hazardous rated housing is available. Hazardous housing is rated to:

  • Class I, Groups B,C,D
  • Class II, Groups E,F,G
  • Class III
  • 4X, 7BCD, 9EFG

and listed as:

  • FM Standard 3615
  • UL Standard 1203
  • CSA Standard C22.2 No. 30
  • NEMA Compliance

Conduit Connection: 1/2" NPT.

Optional Features:

Low Specific Gravity: For application with specific gravity of 0.5 to 0.79, two (2) 2-1/2" round floats are supplied. The insertion length is not increased.
Corrosion-Resistant Coating: To provide added protection in corrosive applications, the float and/or magnetic armatures are available with a Teflon coating.
Dog-Legged Float Rod:The float rod is bent so the high level point is below the face of the control. Typically, the Type A should not be used with liquids containing magnetic particles and/or liquids which will build up on the face of the control.


Starting in the unactuated position, a rising liquid level will lift the float and rod, pivoting the magnetic armature towards the barrier plate. A permanent magnet, located within the switch assembly, snaps forward from the magnetic attraction. In doing so, the plunger is depressed, actuating the switch assembly. When the level decreases, the float falls away, pulling the armature to its original position, releasing the permanent magnet, re-setting the switch assembly to its unactuated position.