How to Guide

Commercial Pressure and Float Switches for Power Circuits

Float Switches—Class 9036, 9037, and 9038

03/2011

Selecting a Float Switch

Standard float switches have two contacts that close when the liquid rises above the designated level.

This contact configuration is used for tank emptying applications. Float switches are also available with

reverse (Form R) and double throw (Form H) contacts. Form R switches, used for tank filling

applications, have two contacts that open when the liquid rises above the designated level. Form H

switches, which can be used for both applications, have one normally open (N.O.) and one normally

closed (N.C.) contact.

To select the proper Square D™ float switch, determine the following:

• Type and shape of tank (open, closed, sump, etc.)

• Enclosure requirements

— NEMA Type 1: For general purpose applications intended for indoor use.

— NEMA Type 4: For watertight and dusttight applications for either indoor or outdoor use.

— NEMA Type 7 and 9: For explosion proof applications. Suitable for Class I, Division 1 and 2,

Groups C and D and Class II, Division 1 and 2, Groups E, F, and G hazardous locations.

• Total level change required

• Mounting requirements (such as flange mounting or screw-in bushing)

• Horsepower, phase, and voltage requirements

• Float material

— Stainless steel (SS)

— Plastic (available on 9036FG30 and as a Form for use with diesel fuel)

• Rod material

—Brass

— Stainless steel (SS)

— Aluminum (Al)

In direct motor control applications, float switch ratings must be greater than or equal to the pump

motor ratings.

NOTE: Contact the Sensor Competency Center when using float switches in liquids with a specific

gravity different than water (1.0).

Specify the Class and Type when ordering float switches or accessory kits.

Selecting Floats and Rods

Class 9036 and Class 9038 Type A float switches are actuated with the Class 9049 Type A line of

accessories. Select the float and rod material according to the corrosiveness of the liquid used in the

application. Two types of float kits are offered:

• Tapped-at-top float (Class 9049 Type A6, A6S, and A6A)

• Center-hole float (Class 9049 Type A6C, A6CS, and A6CA)

The tapped-at-top float is for applications requiring short lengths of tubing and small liquid level

changes. The maximum tubing length is 12 ft (3.66 m). Adequate space must be available to allow for

ceiling clearance when the level changes. The float must be buoyant enough to lift the tubing, stop

collars, and switch lever. The rod has two stops, one above and one below the switch lever. The

position of the stops determines the amount of water level change.

9036DG2

9036GG2