A float switch normally gets attention only after something goes wrong.

A pump starts running without enough liquid. A tank overflows because the high level signal never arrives. A boiler needs low level protection. Or a maintenance team replaces an old switch with another one that physically fits, only to find that the float does not move correctly inside the tank.

This is where magnetic float level switch selection becomes more important than simply matching a thread size.

The Radical TechArt catalogue covers a fairly broad range of magnetic float level switches. The product overview on page 2 shows stainless steel and plastic designs, horizontal and vertical mounting, single and multiple level arrangements, DIN connector versions, adjustable designs and conductivity sensors. Pages 3 to 14 then show the individual float switch families and their application ranges.

The practical question is not, "Which float switch is available?"

It is, "Which construction will actually work inside my tank?"

What Is a Magnetic Float Level Switch?

A magnetic float level switch is a point level sensing device used to detect whether liquid has reached a particular level.

A float moves as the liquid rises or falls. A magnet inside or associated with the float operates a reed switch positioned in the stem. That changes the electrical contact and gives the control system a simple ON/OFF level signal.

In practical terms, the switch can be used for functions such as:

• High level alarm
• Low level alarm
• Tank filling control
• Pump start or stop
• Pump dry run protection
• Overflow prevention
• Minimum level protection
• Multi point level indication

Unlike a continuous level transmitter, a magnetic float switch does not normally tell you that a tank is 37 percent or 68 percent full. It tells the control system that a predefined switching level has been reached.

That distinction matters when selecting between a float switch, ultrasonic level transmitter or hydrostatic level transmitter.

How Does a Magnetic Float Level Switch Work?

The operating principle is mechanically simple.

As liquid reaches the float, buoyancy moves the float along or around its permitted travel. The magnet then changes the state of the internal reed contact.

Depending on the design, the output may be SPST or SPDT. The catalogue also shows configurations where the switching action can be changed by removing the float, reversing its orientation and refitting it on the stem. This is particularly useful when the application requires the contact logic to change between rising and falling liquid conditions.

For automation applications, the contact can be used with:

• PLC digital inputs
• Relays
• Alarm annunciators
• Controllers
• Pump control circuits
• Contactor control circuits where the selected switch rating permits it

The important point is that this is a switching contact, not a 4 to 20 mA continuous output.

Why Selection Matters in Actual Plant Conditions

Two magnetic float level switches can look almost identical and still behave very differently once installed.

For example, a stainless steel float suitable for hot water and pressure may be unnecessary for a simple atmospheric water reservoir. On the other hand, a plastic float chosen only because it costs less may be completely wrong for a hot or pressurized application.

Mounting can create the same problem.

A long top mounted switch may work perfectly in a deep tank but be difficult to remove when there is limited space above the vessel. A compact side mounted design can solve that problem, but only if the tank provides enough internal clearance for the float to move.

A purchase team may compare product price. The maintenance team will eventually deal with the result of the selection.

Main Types of Magnetic Float Level Switches

Rather than treating every model in the catalogue as a separate product, it is more useful to understand the main construction families.

1. Side Mounted Stainless Steel Float Switches

The RDCL-HFS-B-SS and RDCL-HFS-C-SS families are intended for side installation through the tank wall.

These are useful when there is no practical access from the tank top or when the switching point needs to be close to a particular level on the side of the vessel.

The catalogue lists applications such as sterilizers, water boilers, industrial cleaning tanks and kitchen equipment.

Best for: Compact single point high or low level detection in stainless steel process installations.

The HFS-B series is listed with SS 304 / SS 316 construction, temperatures from minus 40°C to 135°C and pressure up to 4 bar. The HFS-C series is also stainless steel, with a smaller diameter seamless float and pressure up to 3 bar.

Main selection point: Check the available space inside the tank for float movement before finalizing a horizontal side mounted design.

2. Flange Mounted Stainless Steel Float Switches

For larger tanks and pressure vessels, the RDCL-HFS-F-SS flange mounted series provides a more substantial mounting arrangement.

The catalogue lists applications including sterilizers, water boilers, pressure vessels and industrial washing machines.

Best for: Larger vessels where flange mounting is preferable to a small threaded process connection.

The listed configuration operates up to 150°C and 5 bar, with stainless steel construction and a ceramic terminal arrangement.

This makes the flange version worth considering when the application condition is beyond the normal range of smaller side mounted products.

3. Side Mounted, Vertically Operated Float Switches

The catalogue also includes designs such as RDCL-VFS-L and RDCL-VFS-S.

These combine side mounting with vertical float movement.

That can be a useful compromise. The installation remains compact from the tank side, but the sensing motion is vertical.

Best for: Boiler protection, chiller units, autoclaves, water treatment systems and applications where switching close to the tank connection is important.

Stainless steel versions are listed for temperatures up to 135°C and pressures up to 4 bar, while Nylon or Polypropylene float versions are intended for lower temperature, atmospheric pressure applications.

4. Top Mounted Single Point Float Switches

The RDCL-MVFS family uses an internal top mounting arrangement.

Top mounting is useful when the tank wall should remain free from additional side penetrations or when the switch needs to reach further down into the vessel.

The catalogue lists water, boiling water, industrial fluids and chemical applications.

Best for: Tanks where sensing depth matters and top access is available.

The range includes full stainless steel and hybrid stainless steel stem with Nylon or Polypropylene float configurations.

5. Adjustable and Multi Level Float Switches

This is where magnetic float technology becomes especially useful for basic tank automation.

The catalogue includes onsite adjustable designs and multi level top mounted versions.

The adjustable type allows switching positions to be fine tuned at site within the available adjustment range. This is useful when the exact high or low level cannot be finalized perfectly during fabrication.

The multi level series can be configured with multiple floats and switching points. The catalogue specifically notes that up to five switching points can be accommodated in the multi level design.

Best for: Applications that need several discrete levels, such as:

• Low low level
• Low level
• Pump start
• Pump stop
• High level alarm

This can sometimes replace several individual switches and reduce the number of tank penetrations.

6. DIN Connector Top Mounted Designs

The external top mounted RDCL-VFS-DIN series uses a DIN connector instead of a permanently attached cable arrangement.

This can make field wiring and replacement cleaner in OEM machines or equipment where connectors are preferred.

The catalogue mentions applications including automotive systems, liquid food applications and printing machinery.

Best for: OEM installations where a compact external electrical termination is preferred.

7. Plastic Float Level Switches

Not every tank needs stainless steel.

The RDCL-HFS-PP and RDCL-SPVFS-PP ranges use engineering plastics such as Nylon and Polypropylene.

The side mounted plastic series is listed for chambers, water reservoirs, water chillers, water coolers, acid tanks and water baths.

The single point top mounted plastic series is intended for oil and chemical applications and is offered with compact threaded mounting options.

Best for: Atmospheric tanks where chemical compatibility and economical construction matter more than pressure capability.

Plastic should not automatically be considered a cheaper substitute for stainless steel. In some chemical applications, the correct plastic can actually be the more appropriate wetted material.

8. External Side Mount Taper Thread Switches

The RDCL-HFS-C-SS-ET and RDCL-HFS-PP-ET designs use a taper thread arrangement intended for quick external side installation.

The catalogue describes the conical thread as helping achieve a simple tank wall fitment and lists a 1/2 inch NPT style connection.

Best for: Simple side mounted installations where fast fitment is important.

Key Selection Factors for a Magnetic Float Level Switch

1. Start With the Liquid

Do not start with the model number.

First confirm:

• Water, oil or chemical
• Liquid temperature
• Tank pressure
• Specific gravity
• Whether the liquid leaves deposits
• Material compatibility

The catalogue shows floats with specific gravity values around 0.70 or 0.85 g/cm³ depending on construction.

This number matters. If the process liquid does not provide enough buoyancy for the selected float, the switch may not actuate correctly.

For liquids with unusual density, always confirm float suitability before ordering.

2. Choose Stainless Steel or Plastic Carefully

Stainless steel versions are the natural choice for many industrial liquids, hot water applications and pressurized systems.

The catalogue commonly uses SS 304 / SS 316 construction and SS 316L stems in several series.

Plastic versions use Nylon or Polypropylene.

A simple rule is:

Material compatibility must still be checked for the actual fluid.

3. Confirm Temperature and Pressure Together

The catalogue does not give one universal rating for every magnetic float switch.

Depending on the family, stainless steel versions are shown with operating temperatures up to 135°C, with the flange mounted series reaching 150°C. Pressure capability varies, with several stainless steel series listed up to 4 bar and the flange type up to 5 bar.

Plastic models are generally shown for atmospheric pressure, with temperature limits commonly up to 100°C. The economical SPVFS series is listed up to 70°C.

This is why selecting by appearance alone is risky.

4. Decide Top Mount or Side Mount

Choose top mounting when:

• The tank already has top access
• A longer sensing depth is required
• Multiple level points are needed
• Side penetration should be avoided

Choose side mounting when:

• Only one particular level needs to be detected
• Installation space above the tank is limited
• The existing tank already has a side nozzle
• The switching point needs to remain close to the tank wall connection

5. Check the Process Connection

The catalogue includes several connection arrangements depending on series, including:

• 1/4 inch BSP
• M10
• M16
• 1 inch BSP
• 1/2 inch NPT
• Flange options
• TC fitting options on selected customizable versions

Do not leave this decision until installation day.

A mechanically correct switch with the wrong process connection is still the wrong switch.

6. Decide How Many Switching Points You Need

For basic overflow protection, one level may be enough.

For pump automation, you may need two levels.

For a more complete tank sequence, multiple switching points may make more sense.

Example:

Middle level: Start filling

High high level: Generate alarm

The catalogue includes customizable multi level arrangements, including designs with up to five switching points.

7. Check Electrical Contact Rating

Switching power varies considerably across the range.

The PDF lists standard ratings from around 10VA on compact economical plastic types to 50VA on several standard models and 70VA on the flange mounted series. Current ratings also vary by model.

The catalogue notes that selected versions can work with contactor loads, but the actual electrical load must always be matched to the selected switch rating.

For PLC applications, the float contact can normally be treated as a discrete input signal through the appropriate control wiring.

Magnetic Float Switch With PLC, HMI and SCADA

A magnetic float level switch does not normally communicate with SCADA directly.

A typical arrangement is:

Float switch contact → PLC digital input → PLC logic → HMI / SCADA

For example, a PLC can use two float switches to control a pump and then display:

• Tank low
• Pump running
• Tank full
• High level alarm

This is often simpler and less expensive than installing a continuous transmitter when the process only requires fixed switching points.

If the operator actually needs a live level percentage or level trend, a continuous level transmitter is usually the more appropriate technology.

Common Applications

The catalogue range covers applications including:

• Water storage tanks
• Water boilers
• Sterilizers
• Industrial cleaning tanks
• Pressure vessels
• Industrial washing machines
• Boiler low level protection
• Feeder tanks
• Chiller systems
• Autoclaves
• Water treatment plants
• Underground tanks
• Water reservoirs
• Fuel tanks
• Automotive applications
• Printing machinery
• Chemical tanks
• Acid tanks
• Oil tanks
• Water coolers and water baths

Common Mistakes to Avoid

1. Selecting only by thread size: The float still needs enough internal tank clearance.
2. Ignoring liquid specific gravity: The float must generate enough buoyancy to switch correctly.
3. Using a plastic model because it is cheaper: Temperature, pressure and chemical compatibility come first.
4. Ignoring switch contact rating: A level switch signal and a motor power circuit are not the same thing.
5. Ordering a fixed switch when the level may change during commissioning: An adjustable version may save rework.
6. Installing multiple individual switches unnecessarily: A multi level assembly may be cleaner when several switching points are required.
7. Not confirming NO, NC or SPDT logic: The mechanical fit may be correct while the control logic is wrong.
8. Treating a float switch as a continuous level transmitter: Use a transmitter when actual continuous level measurement is required.

Do This, Not That

Quick Selection Checklist

Before requesting a quotation, confirm:

1. Liquid name
2. Liquid specific gravity if known
3. Minimum and maximum temperature
4. Tank operating pressure
5. Stainless steel, Nylon or PP requirement
6. Top mount, side mount or flange mount
7. Process connection
8. Required insertion or stem length
9. Number and position of switching points
10. NO, NC, SPST or SPDT contact requirement
11. Electrical voltage and load
12. Cable termination or DIN connector requirement

Installation and Maintenance Points

Leave enough clearance for the float to move freely. Internal pipes, tank walls, agitators and structural parts should not obstruct its travel.

For liquids that can form scale or sticky deposits, periodically inspect the float movement. A reed switch can be electrically healthy while the float itself is mechanically restricted by buildup.

Also check gaskets, cable condition, terminal connections and actual switching response during preventive maintenance.

For pump protection applications, a functional level test is more useful than checking continuity only at the terminal.

Specifications to Confirm Before Purchase

Because the catalogue contains several constructions and customizable versions, final specifications should be confirmed for the exact model before purchase.

Confirm:

• Wetted material
• Float material
• Float dimensions
• Stem length
• Switching level
• Temperature rating
• Pressure rating
• Float specific gravity
• Process connection
• SPST or SPDT requirement
• NO or NC switching logic
• Switching power
• Switching voltage
• Maximum current
• Number of switching points
• Cable type and length
• Connector type
• Gasket material
• Chemical compatibility

Why Buy Magnetic Float Level Switches from Radical TechMart?

A magnetic float switch enquiry often begins with only three details: tank size, liquid and required level.

But choosing the correct model may also require checking mounting orientation, temperature, pressure, float density, process connection, switching logic and electrical load.

At Radical TechMart, the focus is not only on supplying a float switch. The objective is to help match the switch construction to the actual tank and control requirement.

This is particularly useful for OEMs, maintenance teams, system integrators, panel builders, EPC contractors and process plants where a small selection mistake can create unnecessary fabrication or commissioning work.

Final Thoughts

A magnetic float level switch is a simple device, but that simplicity should not lead to casual selection.

For a water tank at atmospheric pressure, a compact plastic switch may be perfectly adequate. For hot liquid, pressure vessels or demanding industrial service, stainless steel may be the better starting point. For multiple alarms and pump commands, a multi level assembly can simplify the installation considerably.

The right magnetic float level switch is selected by understanding the liquid, mounting position, temperature, pressure, buoyancy, switching points and final control circuit, not simply by matching an old model number.

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FAQs

1. What is a magnetic float level switch used for?

A magnetic float level switch detects a predetermined liquid level and provides an electrical contact for alarms, pump control, overflow protection or low level protection.

2. Can a magnetic float switch connect to a PLC?

Yes. Its switching contact can be connected to a suitable PLC digital input. The PLC can then use the signal for pump logic, alarms, HMI indication or SCADA monitoring.

3. What is the difference between top mount and side mount float switches?

Top mounted switches enter vertically from the tank top and are useful for deeper sensing or multiple level points. Side mounted switches are compact and useful for detecting a specific level through the tank wall.

4. Which is better, stainless steel or PP float switch?

Neither is universally better. Stainless steel is commonly used for higher temperature, pressure and demanding industrial applications. Polypropylene can be suitable for atmospheric tanks and selected chemical applications where its compatibility is appropriate.

5. Can one float switch detect several liquid levels?

A single float normally represents a particular switching point, but multi level assemblies can contain several floats and switching points on one stem. The uploaded catalogue includes versions configurable for up to five switching points.

6. Can I use a float switch directly for a pump?

The electrical contact rating must be checked first. In many control systems, the float switch operates a relay, PLC input or contactor control circuit rather than switching the pump motor load directly.

7. Does a magnetic float switch give 4 to 20 mA output?

Normally no. It is a point level switch providing discrete contact status. If continuous liquid level measurement and a proportional signal are required, consider a level transmitter instead.

8. What information should I provide when buying a float level switch?

Provide the liquid, temperature, pressure, specific gravity if available, tank mounting arrangement, process connection, required switching levels, material preference and electrical contact requirement.