LevelAc Switches and Control - SL-400-G Series

LevelAc Switches and Control - SL-400-G Series

SL-400-G Series

Level Ac displacer type level switches, Model SL-400-G are top mounted and use impervious graphite displacers in the control of liquid level under conditions of turbulence or agitation. Wide adjustable differentials on three mercury type switching stations are obtained by setting position of displacers along stainless steel cable.

LevelAc sl-400-g series switch


  • Mounting: Top mounted (See table 1, MODEL NUMBERING)
  • Screwed Connection: 3" - 8 NPT
  • Mounting Flanges: See Model Numbering, Table-5
    • Size: 3", 4" standard
    • Material: Steel - 150 lb. and 300 lb. ANSI Cast Iron - 125 lb. and 250 lb. ANSI Type 304 and 316 Stainless Steel - 150 lb. ANSI
      Note: Other flange sizes, ratings and materials available on order.
  • Displacers: Four, Impervious Graphite
  • Cable: 316 Stainless Steel, 10 ft
  • Clamps: 316 Stainless Steel standard.
  • Magnetic Armature: 430-F corrosion resistant steel
  • Support Spring: Stainless Steel
  • Support Spring Housing: Brass is standard, Stainless Steel is available See table for Model Numbering
  • Spring Retainer: Stainless Steel is standard.
  • Snap Ring: Stainless Steel only.
  • Specific Gravity Ranges: 0.7 to 1.25
  • Temperatures: 300° F (Ambient around displacers and around switch housing)
    NOTE: Since specific gravity and temperature affect calibration, these values must be specified on order.
  • Pressure: Brass Bias Spring Housing : Vacuum to 300 psi @ 300°F
    316 Stainless Steel Bias Spring Housing: 1000 psi @ 100° F ; 800 psi @ 300 ° F.
  • Differential: Adjustable Variable within cable length, 10 ft. standard.

Switch Housing:

  • Explosion-proof: Heavy cast aluminurn base and cover. With drain; NEMA 7A, B, C, D; 8C, D; 9E, F, G; 10; 12; 13.
  • Vapor-proof: Similar to Explosion-proof except with "O" ring seal at base and no drain, NEMA 5; 7C, D; 9E, F, G; 10; 12; 13.
    NOTE - Explosion-proof and Vapor-proof housings are U/L and CSA Approved as float-operated motor control unit for use in hazardous locations.

Switch Stations:

  • Number: Three
  • Type: Mercury only, each equipped with one only SPDT mercury switch.

Principle of Operation

Model SL-400 LevelAc level switches use "heavier-than-liquid" displacers which sink below the surface of the liquid under control. Spring suspension balances the normal displacer weight, and as the liquid level rises around the displacer, it is buoyed up by a force equal to the weight of the liquid displaced. The apparent weight loss allows the spring to move the internal armature into the externally mounted switch's magnetic field to produce switch operation.

Mercury Switching Station - A glass capsule containing the mercury and switch contacts is mounted on a pivoted arm. A magnetic armature moves up and down inside a non-magnetic sealing tube following movement of the float caused by changing liquid level in the float chamber. As the armature enters the field of the Alnico V magnet mounted on the opposite end of the pivoted arm, magnetic attraction causes the magnet to approach the sealing tube and tilt the mercury capsule to make or break an electrical circuit.

Switch Characteristics:

  • Mercury Switch: Hermetically sealed. SPDT mercury capsule switches are standard. Anti-vibration mercury capsules are optional/


Volts AC Amps* AC H.P. AC Pilot Duty DC Amps* DC H.P.
120 13 1/2 345 VA 10 1/2
240 6.5 1 345 VA 5 1/2
400 3 1 345 VA - -

*Anti-vibration switch rating

  • 4 amp @ 120 VAC; 3amp @ 240 VAC
  • 4 amp @ 120 VDC; 2amp @ 240 VDC
  • Internal Wiring: 20 gauge copper (105 strands of no.40 wire for extreme flexbility) insulated with silicone rubber.
  • Terminal Board: Bakelite barrier terminal strip. Terminal positions marked.
  • Switch Frame: Pivot arms and wiring shields are heavy gauge brass. For maximum corrosion resistance, frame may be zinc plated on special order.
  • Magnet: Alnico-V, stabilized.
  • Pivots: Low friction "dog" type. Stainless steel pivot screws.