Measurement and Control Equipment

Mechanical Level Switch: Float-Operated Level Control for Tanks and Boilers

Learn how side-mounted mechanical level switches use float movement to control pumps, solenoid valves and alarms, and explore their types and installation rules.

ORFA Technical TeamUpdated: Oct 30, 20263 min read

Mechanical float level switch for tank level control

Preventing tanks from overflowing, pumps from running dry and boiler water from falling below a set point all require simple but reliable level control. A mechanical level switch is a level control device in which a float mounted through the tank wall moves with the liquid level and opens or closes internal contacts, thereby controlling devices such as pumps, solenoid valves, alarms or signal lamps.

This article explains the working principle, common types, installation rules and applications of mechanical level switches.

What Is a Mechanical Level Switch?

A mechanical level switch consists of a float arm reaching into the tank, a float and switch contacts in the housing actuated by this movement. It works purely by the buoyancy of the float, without electronic adjustment or power supply. This simplicity makes it a common solution for small and medium-sized tank and boiler applications.

Working Principle

Float movement: The float rises as the level rises and falls as it drops.
Contact actuation: The movement of the float arm actuates the switch contacts in the housing (micro switches or magnetic contacts, depending on the model).
Circuit control: The contact opens or closes, switching a pump, solenoid valve, alarm or signal lamp on or off.

Tip: If the switch is to control large loads such as a pump motor, connect the load through a contactor so the contact rating is not exceeded. Check the contact rating on the product label or in the catalogue.

Common Types

Type	Connection	Key features
Ayvaz C-2	Threaded (1″)	Compact; up to 6 bar and 125 °C; 15–90 mm control range; stainless steel float
Ayvaz C-4	Flanged	PN6 and PN16 versions; options with adjustment mechanism or PTFE coating

Exact limits and contact ratings depend on the model and should be confirmed in the product catalogue before selection.

Advantages

Simple and reliable: Mechanical operation with no electronic circuitry.
Adjustable switching range: The float arm and adjustment mechanism set the on/off differential.
Leak-tight design: Housing and connection are designed to seal against the tank pressure.
Flexible contacts: Normally open and normally closed contacts allow use for both filling and emptying control.
Long life: Stainless steel float and durable housing materials.

Installation

Mechanical level switches are usually mounted horizontally through the tank wall.
Install near the top of the tank for high-level control and near the bottom for low-level control.
Choose a position where the float can move freely and the filling stream does not hit it directly.
Wire the NO/NC contacts according to whether the switch is used for filling (pump starts when the level falls) or emptying (pump starts when the level rises).

Applications

Pressurised and unpressurised vessels
Fresh water and waste water tanks
Fuel tanks
Steam generators and small steam boilers
Hot water boilers
Booster set tanks
Water treatment systems

Frequently Asked Questions

Where is a mechanical level switch installed?

Usually horizontally through the tank wall: near the top for high level and near the bottom for low level.

Can one switch be used for both filling and emptying?

Yes. The switches have normally open and normally closed contacts, so depending on the wiring they can control filling or emptying.

What is the main difference between C-2 and C-4?

The C-2 is a compact switch with a threaded connection. The C-4 has a flanged connection, PN6 and PN16 pressure ratings, and options with an adjustment mechanism or PTFE coating.

Conclusion

With a simple design and reliable operation, mechanical level switches are a practical solution for pump, valve and alarm control in tank, boiler and booster set applications. Choosing the right type, pressure-temperature rating and mounting position ensures long service life. Explore more level control solutions on our Level Control Devices page and contact the ORFA technical team for support.

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