//bat.bing.com/action/0?ti=5562332&Ver=2

Float Switch Guide and Float Switch Products

Madison Company offers the most extensive line of liquid level sensor solutions and customer support. We can provide a stock float switch the same day, or design a customized OEM float switch in 3 days. View In-Stock products available for same-day shipping »

Float Switch Operation

A magnetic float travels up and down the stem between float stops actuating or de-actuating a dry contact reed switch encapsulated inside the stem. When the magnetic field comes in close proximity to the reed switch, the float switch contact closes.  These reed switch based float switches typically activate with a 1/16" of movement, with overtravel to keep the in proper setting as the liquid level rises or falls.

Float Switch operation is determined in a dry condition (Empty Tank) with the installation fitting up and the float at rest against the lower float stop for vertical float switches.  For horizontally mounted float switches, the float switch assembly can be rotated 180 degrees for normally open or normally closed operation.

Normally Closed (NC): Float Switch is closed circuit before fluid is present and will open on the rise of liquid level.
Normally Open (NO): Float Switch open circuit before fluid is present at the float and will close on the rise of liquid level.

NOTE: Madison Company vertical float switches are supplied in the normally closed (NC) position, unless otherwise specified.

Vertical Float Switch Position Horizontal Float Switch Position Electrical Circuit Diagram
Normally openNC Plastic Side Mnt NC-NO Float Switch Electrical Diagram

Typical Float Switch Installation Fittings

Madison multi-point float switches are available with bulkhead, male thread, male pipe plug or flange mounting. These float switches may be mounted with the stem at up to a 30° angle from the vertical position.

Multi Ref 1

Offset Stems

Obstructions in tanks and difficult mountings often require bending the tube to allow proper installation. Madison's engineering staff can design float switches with offset stems to solve many types of installation problems. Most metal stems are available with offset configurations.

ML Offset

Turbulence

Intensive agitation of liquid, boiling fluids and surging due to large inflows of liquid can all cause turbulence and erratic float switch operation. This problem can be eliminated by the use of slosh shields with adequately-sized fluid and vent holes, as illustrated here. Available for vertical, horizontal (side-mounted) and multi-point float switches with full-size or miniature floats, these slosh shields can be supplied in stainless steel, brass, polypropylene, PBT or Kynar.

PS Turb 1

Environmental Protection

International Protection Codes (IP)

IP numbers are used to specify the environmental protection of enclosures around electronic equipment.

First Number

  • 0 - No protection (sometimes X)
  • 1 - Protected against solid objects up to 50mm2
  • 2 - Protected against solid objects up to 12mm2
  • 3 - Protected against solid objects up to 2.5mm2
  • 4 - Protected against solid objects up to 1mm2
  • 5 - Protected against dust, limited ingress (no harmful deposit)
  • 6 - Totally protected against dust

Second Number

  • 0 - No protection (sometimes X)
  • 1 - Protected against vertically falling drops of water (i.e. condensation)
  • 2 - Protected against direct sprays of water up to 15° from vertical
  • 3 - Protected against direct sprays of water up to 60° from vertical
  • 4 - Protected against water sprayed from all directions - limited ingress permitted
  • 5 - Protected against low-pressure jets of water from all directions - limited ingress permitted
  • 6 - Protected against low-pressure jets of water, limited ingress permitted (i.e. ship deck)
  • 7 - Protected against the effect of immersion between 15cm and 1m
  • 8 - Protected against long periods of immersion under pressure

NEMA

  • National Electrical Manufacturers Association (NEMA) Standards Publication No. 250 guidelines are as follows:
  • NEMA 1 Indoor Use Protects against accidental contact by personnel and falling dirt
  • NEMA 2 Indoor Use Protects against falling dirt, liquid and light splash
  • NEMA 3 Outdoor Use Protects against rain, sleet, snow, dirt and dust
  • NEMA 3A Outdoor Use Protects against rain, sleet, snow, dirt and ice buildup
  • NEMA 4 In- or Outdoor Protects against dirt, dust, hosedown and heavy splash
  • NEMA 4X In- or Outdoor Protects against dirt, dust, hosedown and
  • prolonged submersion
  • NEMA 6 In- or Outdoor Protects against dirt, dust, hosedown and occasional submersion
  • NEMA 6P In- or Outdoor Protects against dirt, dust, hosedown and prolonged submersion
  • NEMA 7 Indoor Use For use in areas of explosive gases or vapors or combustible dust
  • NEMA 9 Indoor Use For use in areas of atmospheres containing combustible dust
  • NEMA 12 Indoor Use Protects against dirt, dust, light splash and oil or coolant seepage
  • NEMA 13 Indoor Use Protects against dirt, dust, light splash and oil or coolant spray