Baumer Float Level Switch Selection Guide: Choosing Between LA and LZ
A tank has to stop filling before it overflows. A pump should not continue running when the liquid level becomes too low. A process vessel needs a high-level alarm. A wastewater sump needs automatic pump control.
All of these sound like straightforward level switching applications.
The mistake happens when the buyer simply asks for a "float switch" without considering how the switch will be mounted, what liquid is inside the vessel, operating temperature, pressure, required switching point and installation environment.
A cable float hanging inside a water tank and a stainless steel side-mounted float fitted into a process vessel perform the same basic job, but they are meant for very different installations.
Within the Baumer float level switch range covered by the available datasheets, this difference is clearly seen between the LZ Cable Float Level Switch and the LA Side Mounted Level Switch. The LZ is designed around a suspended polypropylene float and cable arrangement, while the LA uses a side-mounted float mechanism with AISI 316 stainless steel wetted parts and a magnetic switching principle.
That distinction should be the starting point of selection.
What Is a Baumer Float Level Switch?
A float level switch detects whether liquid has reached a particular level and changes an electrical contact accordingly.
Unlike a continuous level transmitter, it does not tell the control system that the tank is 42% or 78% full. Its job is to give a switching condition such as:
In a typical control panel, this switching contact can become part of a relay, contactor, alarm or PLC digital input circuit, depending on the electrical design.
The important question is therefore not only, "Do I need a float switch?"
It is, "What type of float switch suits this vessel and process?"
Baumer LZ Cable Float Level Switch
The LZ is the simpler choice when the float can hang freely inside a tank, sump or reservoir.
As the liquid rises or falls, the float tilts. That movement operates an internal microswitch and changes the contact from normally open to normally closed or vice versa. Baumer also shows the LZ being used for filling control and pump protection, which makes its intended use very clear.
Best for:
Water tanks, sewage tanks, reservoirs, sumps and automatic pump control applications where a suspended cable float can move freely with liquid level.
Why the LZ makes sense
The strength of the LZ is simplicity.
You do not need a side process flange penetrating the vessel. The float is suspended from its cable, and the adjustable counterweight helps define how the float moves around the required switching level.
This makes it practical for larger tanks where the level differential does not need to be extremely tight.
Its polypropylene construction also suits the water and sewage applications identified in the datasheet. The enclosure is IP68, which is particularly relevant because the float operates directly in the liquid environment.
Technical points to note
| Parameter | Baumer LZ |
|---|---|
| Type | Cable float level switch |
| Float and counterweight | Polypropylene |
| Cable | PVC |
| Standard cable length | 3 metre |
| Other listed cable lengths | 5, 10 and 20 metre |
| Enclosure | IP68 |
| Mounting | Vertical |
| Switch | SPDT |
| Electrical rating | 16 A, 250 VAC |
| Maximum operating pressure | 4 bar |
| Maximum operating temperature | Up to 60°C |
Baumer notes that cable lengths above 20 metres should be discussed with the factory.
Where the LZ is commonly used
Its datasheet specifically identifies sewage and water treatment plants, storage tanks and automatic pump control utilities. The same operating principle makes it relevant wherever a freely suspended float can be used for high or low level switching.
For example, in a sump pump application, one LZ can be positioned to create the required switching point. Where multiple level points are necessary, the datasheet also states that the LZ can be used as a multipoint switch arrangement.
Selection caution
Do not select the LZ simply because the application contains water.
Check whether the float has enough free space to move without hitting a wall, ladder, pipe, agitator or other internal structure. Also confirm liquid temperature and pressure because the standard version is specified up to 60°C and 4 bar.
For compact vessels requiring a precise side switching point, the LA arrangement may make more sense.
Baumer LA Side Mounted Float Level Switch
The LA belongs to a different class of installation.
Instead of hanging from a cable, it is fitted through the side of the vessel. A free-moving float operates a magnetic mechanism. The datasheet describes two magnets, one associated with the float arm and another in the switch enclosure. Changing liquid level brings the magnetic poles into a position where repulsion produces a snap-action changeover contact.
Best for:
Process tanks and vessels where a defined side-mounted level point is required, particularly where stainless steel wetted parts, higher temperature capability or higher operating pressure are needed.
Why the LA makes sense
A side-mounted switch gives the engineer a defined physical switching location.
If the requirement is "give me a high-level alarm at this nozzle" rather than "switch somewhere across this suspended cable travel," a side-mounted design is generally much easier to engineer into the vessel.
The standard LA uses AISI 316 stainless steel wetted parts, a 92 mm PCD square flange and a 215 mm standard insertion depth. Its standard operating specification extends from -10°C to +180°C with a maximum pressure of 18 kg/cm² and a minimum liquid specific gravity of 0.75.
That immediately places it in a different application range from the LZ.
Technical points to note
| Parameter | Baumer LA Standard Version |
|---|---|
| Mounting | Side mounted |
| Housing | Die cast aluminium |
| Ingress protection | IP65 |
| Standard process connection | 92 mm PCD square flange |
| Wetted parts | AISI 316 SS |
| Float diameter | 45 mm, 48 mm at welded seam |
| Standard insertion depth | 215 mm |
| Minimum specific gravity | 0.75 |
| Operating temperature | -10°C to +180°C |
| Maximum operating pressure | 18 kg/cm² |
| Switch differential | 15 ± 5 mm |
| Switch | Microswitch |
| Switch rating | 5 A, 250 VAC |
Where the LA is commonly used
Baumer identifies applications including chemical processing equipment, alarms for hydro-pneumatic tanks, shipbuilding, water treatment plants, food and pharmaceutical applications.
These applications make sense because the LA is designed around a process-mounted construction rather than a freely suspended plastic float.
LA variants matter when the standard model is not enough
The LA family is not limited to one configuration.
Baumer lists:
Type A: General-purpose standard version
Type T: High-temperature version, up to 350°C, using aluminium cooling fins
Type Z: Adjustable differential version
The minimum insertion depth is 215 mm for Types A and T, while Type Z starts from 350 mm. The ordering information also provides alternatives for housing, cable glands, switch output and process connections. Standard switch output is 1 SPDT, with 2 SPDT / 1 DPDT available as another listed configuration.
This is useful in projects where the requirement is more specific than a standard high or low level switch.
Selection caution
The minimum specific gravity of 0.75 must not be ignored.
A float works only when the liquid can provide sufficient buoyancy. Before ordering the LA, Baumer specifically asks for the liquid, specific gravity, operating pressure and operating temperature along with the model information.
That is good purchasing practice even when replacing an existing switch.
Baumer LA vs LZ: Which Float Level Switch Should You Choose?
| Selection Point | LZ Cable Float | LA Side Mounted |
|---|---|---|
| Installation style | Suspended inside tank | Installed through vessel side |
| Best suited to | Tanks, reservoirs, sumps, pump control | Process tanks and vessels |
| Standard wetted construction | Polypropylene float | AISI 316 SS |
| Protection | IP68 | IP65 standard |
| Maximum temperature | Up to 60°C | Up to 180°C standard, Type T up to 350°C |
| Maximum pressure | 4 bar | 18 kg/cm² standard |
| Switching arrangement | SPDT | SPDT standard, additional output option listed |
| Level differential | Determined through cable float arrangement | 15 ± 5 mm standard, Type Z adjustable |
| Main buying advantage | Simple tank and pump control installation | Defined process mounting and broader process capability |
In simple words, choose the LZ when you need a practical cable float inside a tank. Choose the LA when you need an engineered switching point on the side of a process vessel.
Key Selection Factors for a Baumer Float Level Switch
1. Start With the Tank, Not the Model Number
First determine whether the vessel allows a freely hanging float.
A large water storage tank or sump may suit an LZ very well. A compact process vessel with a dedicated side nozzle naturally points toward the LA.
2. Check the Liquid
For the LA, specific gravity matters because the standard minimum is 0.75. Also consider whether the wetted material is compatible with the liquid. The standard LA uses AISI 316 SS wetted parts, while the LZ uses a polypropylene float.
3. Check Temperature Before Anything Else
This is one of the easiest ways to separate the two products.
An application near ambient water temperature is very different from a hot process vessel.
The LZ standard version is specified up to 60°C. The LA standard version reaches +180°C, while the Type T configuration is listed for temperatures up to 350°C.
4. Confirm Operating Pressure
Do not use tank dimensions as a substitute for pressure information.
The LZ standard specification lists a maximum operating pressure of 4 bar. The LA standard version lists 18 kg/cm².
5. Decide the Required Switching Differential
A pump control application may intentionally need significant difference between ON and OFF levels to avoid rapid cycling.
A process alarm may require a much more defined switching point.
This is where the physical arrangement of LZ and LA becomes important.
6. Confirm the Electrical Circuit
Both products provide switch contacts rather than a continuous analogue level signal.
Before connecting the switch to a PLC, relay or pump control circuit, confirm the required contact logic, voltage and current. The LZ is listed as SPDT rated 16 A at 250 VAC, while the standard LA microswitch is rated 5 A at 250 VAC.
Common Mistakes to Avoid
The most common mistake is ordering by the words "float switch" alone.
Also avoid selecting the LZ without checking whether it has enough movement inside the tank, ignoring the LA's specific gravity requirement, choosing a switch without checking process temperature and pressure, assuming IP68 and IP65 mean the products can be used interchangeably, and replacing an old side-mounted switch without confirming process connection and insertion depth.
For pump applications, also consider the actual start and stop logic before installation. A switch that operates correctly at the wrong elevation is still the wrong installation.
Do This, Not That
| Do This | Not This |
|---|---|
| Select mounting style from the vessel design | Buy any float switch based on price |
| Confirm liquid specific gravity for the LA | Assume every liquid will operate the float |
| Check actual process temperature and pressure | Select from tank capacity alone |
| Confirm switch logic and electrical rating | Assume every contact suits every load |
| Check cable travel and obstructions for LZ | Let the float hit the tank wall or piping |
| Confirm LA process connection and insertion depth | Order only from an old model name |
| Select differential according to control requirement | Treat pump control and alarm duty as identical |
Quick Selection Checklist
Before sending an inquiry for a Baumer float level switch, confirm the liquid, tank or vessel type, side-mounted or suspended installation, high-level or low-level function, operating temperature, operating pressure, liquid specific gravity where applicable, required switching differential, electrical contact requirement, process connection for LA, cable length for LZ and whether the application is alarm duty or automatic pump control.
Providing these details usually makes model selection much faster.
Why Buy Baumer Float Level Switches from Radical TechMart?
A float level switch is inexpensive compared with the pump, vessel or process it protects, but incorrect selection can still create repeated operating problems.
At Radical TechMart, the focus is to help buyers identify whether the application needs a simple cable float such as the Baumer LZ or a process-mounted switch such as the Baumer LA, then confirm the important operating conditions before quotation.
Support can include product selection, datasheet clarification, model configuration, pricing and availability for water treatment companies, OEMs, EPC contractors, process industries, maintenance teams and industrial purchase departments.
Final Thoughts
The best Baumer float level switch is not automatically the model with the higher temperature rating or more options.
For a water tank or sump, the simpler LZ cable float may be exactly what the application needs. For a pressurised process vessel, chemical application or defined side-mounted switching point, the LA can be the more appropriate choice.
The selection becomes straightforward once you answer four questions first: What is the liquid, where will the switch be mounted, what are the temperature and pressure, and exactly what level action should occur?
That is a much better way to select a float level switch than starting with price or model number.
FAQs
1. What is a Baumer float level switch used for?
A Baumer float level switch is used for point level detection such as high-level alarm, low-level alarm, filling control, pump start, pump stop and pump protection.
2. What is the difference between Baumer LA and LZ level switches?
The LZ is a cable float that hangs inside the tank and tilts as the level changes. The LA is a side-mounted process level switch using a float arm and magnetic snap-action switching mechanism.
3. Which Baumer level switch is suitable for a water tank?
For a storage tank or reservoir where a suspended float can move freely, the LZ is specifically identified by Baumer for storage tanks, sewage and water treatment and automatic pump control.
4. Which Baumer float switch is better for high-temperature applications?
The LA offers greater temperature capability. Its standard version is specified up to +180°C, while the Type T high-temperature configuration is listed up to 350°C.
5. Can a Baumer float switch be connected to a PLC?
The products provide switch contacts that can typically be incorporated into industrial control circuits. The final PLC input wiring or interposing relay arrangement should be designed according to the PLC input specification and the switch contact rating.
6. What cable lengths are available for the Baumer LZ?
The datasheet lists 3 metres as standard, with 5, 10 and 20 metre versions. For lengths above 20 metres, Baumer advises consulting the factory.
7. What specific gravity is required for the Baumer LA?
The standard LA datasheet specifies a minimum specific gravity of 0.75.
8. What information should I provide when requesting a Baumer LA level switch?
Baumer's ordering information asks buyers to specify the model number, liquid, specific gravity, operating pressure and operating temperature. Process connection, insertion depth, housing and switch output should also be selected according to the required configuration.
