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Danfoss RT Series Pressure Switch Selection Guide for Industrial Applications

Sat, 23 May 2026 08:24:41 +0000

Danfoss RT Pressure Switch | RT 5, RT 110, RT 112, RT 116, RT 121, RT 200

A pressure switch is usually noticed only when something goes wrong: a pump does not cut off, a compressor keeps running, a boiler safety circuit trips, or a hydraulic unit gives unstable operation. In many factories, the mistake is not that a pressure switch was used. The mistake is that the wrong pressure range, reset type, differential, enclosure rating, or process connection was selected.

The Danfoss RT Series Pressure Switch is used in industrial and marine applications where pressure needs to trigger an electrical switching action. The RT range includes pressure switches, differential pressure switches, neutral-zone regulation switches, and safety pressure switches for specific boiler plant applications. Danfoss describes RT pressure switches as pressure-controlled, single-pole changeover switches where contact position depends on pressure at the connection port and the set value.

This guide focuses on commonly used RT pressure switch models available for industrial selection: Danfoss RT 5, RT 110, RT 112, RT 116, RT 121, and RT 200.

Below details are based on the available information. Final specification should be confirmed from the official datasheet before purchase.

What is a Danfoss RT Series Pressure Switch?

A Danfoss RT pressure switch is an electromechanical pressure switch used to make or break an electrical circuit when pressure reaches a set point. In simple words, it converts pressure condition into a switching command.

Typical use cases include:

Pump ON/OFF control
Compressor cut-in / cut-out control
Hydraulic power pack protection
Lubrication oil pressure monitoring
Boiler and burner safety interlock
Vacuum or suction pressure monitoring
Alarm signalling to control panels
Marine and industrial equipment protection

Most RT pressure switch models use SPDT contact function, which means the switch can be wired as normally open or normally closed depending on the control logic. For many control panels, this is useful because the same switch can be adapted for alarm, trip, interlock, or start-stop logic.

Why RT Series Selection Matters in Actual Plant Conditions

A pressure switch is not selected only by pressure range. The real selection depends on how the switch will behave when the system pressure rises or falls.

For example, a pump protection application may need automatic reset after pressure normalizes. A high-pressure safety application may require manual reset so the system does not restart without operator checking. A vacuum application needs a negative pressure range, while a compressor application needs a range that covers cut-in and cut-out points with the correct differential.

This is where many buyers make a mistake. They ask for “Danfoss RT pressure switch” but do not confirm:

Required pressure range
Cut-in and cut-out pressure
Adjustable or fixed differential
Auto reset or manual reset
Process media
Process connection
Enclosure rating
Electrical load
Panel wiring logic
Whether the switch is for control, alarm, or safety

A purchase team may compare price, but the maintenance team will face the result if the switch trips incorrectly or does not reset as expected.

Danfoss RT Series Models Covered

Model	Typical Selection Meaning
Danfoss RT 5	Higher pressure control applications where manual maximum reset may be required
Danfoss RT 110	Low-pressure monitoring where manual minimum reset is needed
Danfoss RT 112	Low-pressure automatic reset applications
Danfoss RT 116	Medium-pressure automatic reset applications
Danfoss RT 121	Vacuum / negative pressure applications
Danfoss RT 200	General 0.2–6 bar pressure control applications

Danfoss RT 5

Danfoss RT 5 is useful when the application requires pressure switching in a higher range compared to low-pressure models. It is often considered where pressure rise must be monitored and a manual maximum reset is preferred so the system does not restart without operator attention.

Best for:

Compressor, pump, hydraulic, and safety-related pressure applications where high-pressure trip action may need manual reset.

Why this model makes sense:

RT 5 has a regulation range of 4–17 bar, fixed differential of 1.2 bar, SPDT contact function, manual maximum reset, G 3/8 male pressure connection, IP54 enclosure rating, and 22 bar maximum working pressure according to Danfoss store data. This makes it suitable when the process operates in a higher pressure band and the user wants manual acknowledgement after high-pressure operation.

Technical points to note:

Regulation range: 4–17 bar
Differential: 1.2 bar
Contact function: SPDT
Reset function: Manual Max
Pressure connection: G 3/8 male
Enclosure rating: IP54
Maximum working pressure: 22 bar
Confirm exact code and variant before ordering

Where it is commonly used:

Air compressor systems
Hydraulic power packs
Pump discharge pressure monitoring
Industrial machinery protection
Utility pressure panels
High-pressure alarm circuits

Selection caution:

Do not choose RT 5 only because it is a “high pressure switch.” Confirm the required trip point, reset philosophy, enclosure protection, and whether IP54 is suitable for the installation area.

Danfoss RT 110

Danfoss RT 110 is suitable for low-pressure applications where the system must not resume operation automatically after pressure drops below a set point. This is useful in protection logic where low pressure indicates a fault condition.

Best for:

Low-pressure protection, lubrication oil pressure monitoring, pump suction protection, and applications needing manual minimum reset.

Why this model makes sense:

RT 110 has a regulation range of 0.2–3 bar, 0.08 bar differential, SPDT contact function, manual minimum reset, G 3/8 male pressure connection, IP54 enclosure rating, and 7 bar maximum working pressure according to Danfoss store data.

Technical points to note:

Regulation range: 0.2–3 bar
Differential: 0.08 bar
Contact function: SPDT
Reset function: Manual Min
Pressure connection: G 3/8 male
Enclosure rating: IP54
Maximum working pressure: 7 bar
Useful where low-pressure fault must be manually acknowledged

Where it is commonly used:

Lubrication oil pressure protection
Low-pressure pump circuits
Burner or boiler auxiliary systems
Compressor auxiliary pressure monitoring
Industrial safety interlocks
Control panel alarm circuits

Selection caution:

Before selecting RT 110, confirm whether the process should restart automatically or only after manual reset. Wrong reset selection can create nuisance downtime or unsafe restart logic.

Danfoss RT 112

Danfoss RT 112 is better suited when the pressure range is low and automatic reset is acceptable. It is practical for low-pressure control or alarm applications where the switch should return to normal after pressure recovers.

Best for:

Low-pressure automatic reset control in pump, utility, HVAC, and industrial process systems.

Why this model makes sense:

RT 112 has a regulation range of 0.1–1.1 bar, adjustable differential of 0.07–0.16 bar, SPDT contact function, auto reset, G 3/8 male pressure connection, IP66 enclosure rating, and 7 bar maximum working pressure according to Danfoss store data.

Technical points to note:

Regulation range: 0.1–1.1 bar
Differential: 0.07–0.16 bar
Contact function: SPDT
Reset function: Auto
Pressure connection: G 3/8 male
Enclosure rating: IP66
Maximum working pressure: 7 bar
Better suited where pressure recovery can automatically restore the contact condition

Where it is commonly used:

Low-pressure pump systems
Air or water pressure monitoring
Utility pressure alarms
HVAC auxiliary pressure monitoring
Industrial process panels
Low-pressure control circuits

Selection caution:

RT 112 is not the right choice if the process needs operator acknowledgement after a low-pressure fault. In that case, a manual reset model may be more suitable.

Danfoss RT 116

Danfoss RT 116 is a practical medium-pressure switch for applications where the operating set point falls within the 1–10 bar range. It is useful for pump control, compressor auxiliary control, and general industrial pressure monitoring.

Best for:

General industrial pressure control where automatic reset and adjustable differential are required.

Why this model makes sense:

RT 116 has a regulation range of 1–10 bar, adjustable differential of 0.33–1.3 bar, SPDT contact function, auto reset, G 3/8 male pressure connection, IP66 enclosure rating, and 22 bar maximum working pressure according to Danfoss store data.

Technical points to note:

Regulation range: 1–10 bar
Differential: 0.33–1.3 bar
Contact function: SPDT
Reset function: Auto
Pressure connection: G 3/8 male
Enclosure rating: IP66
Maximum working pressure: 22 bar
Suitable for common industrial pressure bands

Where it is commonly used:

Pump pressure control
Compressor pressure monitoring
Hydraulic auxiliary circuits
Industrial water systems
Utility pressure panels
Process equipment pressure alarms

Selection caution:

Before selecting RT 116, calculate the required cut-in and cut-out pressure. Differential setting is important; wrong differential can cause rapid cycling or delayed switching.

Danfoss RT 121

Danfoss RT 121 is used when the process condition is below atmospheric pressure. This makes it suitable for vacuum or suction-side monitoring where normal positive-pressure switches are not suitable.

Best for:

Vacuum monitoring, suction pressure protection, and negative pressure applications.

Why this model makes sense:

RT 121 has a regulation range of -1 to 0 bar, differential of 0.09–0.4 bar, SPDT contact function, auto reset, G 3/8 male pressure connection, IP66 enclosure rating, and 7 bar maximum working pressure according to Danfoss store data.

Technical points to note:

Regulation range: -1 to 0 bar
Differential: 0.09–0.4 bar
Contact function: SPDT
Reset function: Auto
Pressure connection: G 3/8 male
Enclosure rating: IP66
Maximum working pressure: 7 bar
Selected specifically for vacuum / negative pressure conditions

Where it is commonly used:

Vacuum systems
Pump suction monitoring
Filter blockage indication
Process suction lines
Packaging machinery vacuum circuits
Industrial utility vacuum panels

Selection caution:

Do not use a normal positive-pressure switch for a vacuum application. Confirm whether the pressure value is gauge pressure, vacuum pressure, or absolute pressure before selection.

Danfoss RT 200

Danfoss RT 200 is a general-purpose pressure switch for lower-to-medium pressure applications where the range is around 0.2–6 bar. It is commonly considered for pump, air, water, and utility pressure switching.

Best for:

General industrial pump and pressure control where 0.2–6 bar range and automatic reset are suitable.

Why this model makes sense:

One Danfoss RT 200 variant is listed with 0.2–6 bar regulation range, 0.25–1.2 bar differential, SPDT contact function, auto reset, G 3/8 male pressure connection, IP66 enclosure rating, and 22 bar maximum working pressure. Danfoss also lists RT 200 product details such as 25 bar maximum test pressure, 22 bar maximum working pressure, G 3/8 connection, bellows pressure sensing element, and IP66 enclosure rating for a related RT200 product code.

Technical points to note:

Regulation range: 0.2–6 bar
Differential: 0.25–1.2 bar
Contact function: SPDT
Reset function: Auto on one common variant
Pressure connection: G 3/8 male
Enclosure rating: IP66
Maximum working pressure: 22 bar
Confirm exact code, because reset function may vary by product variant

Where it is commonly used:

Pump control systems
Water pressure monitoring
Compressor auxiliary circuits
Industrial utility panels
Air pressure control
Process pressure alarms

Selection caution:

RT 200 is a good general range model, but confirm the exact product code because RT 200 variants may differ in reset type and configuration.

Key Selection Factors for Danfoss RT Pressure Switches

1. Pressure Range

The selected pressure switch range should comfortably cover the actual operating set point. Do not select a switch where the set point is at the extreme edge of the scale.

2. Differential

Differential is the gap between switching point and reset point. Too small a differential may cause frequent switching. Too large a differential may delay response.

3. Reset Type

Auto reset is useful for normal control. Manual reset is better for safety or fault conditions where operator inspection is required.

4. Contact Function

Most models listed here use SPDT contact logic, useful for panel wiring as NO or NC depending on alarm or control requirement.

5. Enclosure Rating

IP66 is better for harsh, dusty, humid, or outdoor-type locations than IP54, but exact site conditions should always be checked.

6. Process Connection

The listed models commonly use G 3/8 male connection, but confirm whether your installation needs an adapter, isolation valve, siphon, snubber, or gauge cock.

7. Media Compatibility

Confirm whether the switch is being used with air, water, oil, steam, refrigerant, or another process media. Media temperature and compatibility must match the datasheet.

8. Electrical Load

Check whether the switch is switching a relay/contactor coil, PLC digital input, alarm circuit, or direct load. Use interposing relays where needed.

Common Applications

Danfoss RT Series pressure switches are commonly used in:

Air compressors
Industrial pumps
Hydraulic power packs
Boiler and burner systems
Marine machinery
HVAC and utility systems
Lubrication oil pressure monitoring
Water treatment systems
Process pressure alarms
OEM machine panels
Control and safety interlock panels

Common Mistakes to Avoid

Mistake	Why It Creates Problems
Selecting only by model number	Old installation may have used a variant that is not ideal for the current application
Ignoring reset type	Auto reset and manual reset behave differently in safety circuits
Not checking differential	Wrong differential can cause short cycling or delayed switching
Choosing the wrong pressure range	Accuracy and switching behavior may suffer near scale extremes
Ignoring IP rating	Dust, humidity, and outdoor exposure can reduce switch life
Not checking process connection	Installation may require adapter or isolation accessory
Using switch output like transmitter output	Pressure switches give relay/contact action, not continuous 4–20 mA pressure signal
Not confirming datasheet	Product codes and variants can change selection details

Do This, Not That

Do This	Not This
Select the model based on actual set point and differential	Select only by “RT Series” name
Confirm auto reset or manual reset requirement	Assume every pressure switch resets automatically
Use RT 121 for vacuum range applications	Use a positive pressure switch for suction/vacuum service
Confirm enclosure rating and installation area	Install IP54 model in a wet or harsh area without checking
Check wiring with PLC, relay, or contactor logic	Assume contact rating and wiring are always suitable
Confirm exact Danfoss code before purchase	Order only from partial model name

Quick Selection Checklist

Confirm whether the application is pressure, vacuum, or differential pressure.
Note the normal operating pressure, alarm point, cut-in, and cut-out pressure.
Select the correct pressure range with margin.
Confirm required differential.
Decide whether auto reset or manual reset is required.
Check SPDT wiring logic for PLC, relay, contactor, or alarm panel.
Verify process connection and adapter requirement.
Confirm IP rating and installation environment.
Check media compatibility and temperature condition.
Confirm exact Danfoss product code and datasheet before ordering.

Specifications to Confirm Before Purchase

Before buying any Danfoss RT Series pressure switch, confirm:

Exact model and product code
Pressure regulation range
Differential range
Reset function: auto, manual minimum, or manual maximum
Contact function and contact rating
Process connection size and type
Maximum working pressure
Maximum test pressure
Enclosure rating
Ambient temperature range
Media temperature range
Media compatibility
Electrical cable entry
Mounting arrangement
Required approval or certification
Compatibility with PLC, relay, contactor, alarm, or safety circuit

Why Buy from Radical TechMart?

At Radical TechMart, the focus is not only to supply the product, but to help customers select the right instrument for the right application.

For Danfoss RT Series pressure switches, correct selection matters because the same product family includes different pressure ranges, reset types, enclosure ratings, and application roles. A buyer may ask for Danfoss RT 116 or RT 200, but the final choice should depend on actual process pressure, switching logic, installation environment, and maintenance requirement.

Radical TechMart can support OEMs, factories, system integrators, panel builders, EPC contractors, MRO teams, and process industries with product selection, pricing, availability, datasheet support, and technical inquiry guidance.

Final Thoughts

The Danfoss RT Series is a strong choice for industrial pressure switching, but the right model must be selected by application logic. RT 5, RT 110, RT 112, RT 116, RT 121, and RT 200 are not interchangeable just because they belong to the same series. Each model fits a different pressure band, reset requirement, and control purpose.

In industrial applications, the right pressure switch is not selected only by price or model number. It is selected by understanding the process, the pressure range, the switching logic, the environment, and the final control requirement.

FAQs

1. What is the use of Danfoss RT Series pressure switch?

Danfoss RT Series pressure switches are used to switch an electrical contact when pressure reaches a set value. They are commonly used in pumps, compressors, hydraulic systems, boiler plants, marine systems, and industrial control panels.

2. What is the difference between Danfoss RT 116 and RT 200?

RT 116 is commonly selected for 1–10 bar applications, while RT 200 is commonly selected for 0.2–6 bar applications. Final selection should be based on set pressure, differential, reset type, and exact product code.

3. Which Danfoss RT model is suitable for vacuum applications?

Danfoss RT 121 is suitable for vacuum or negative pressure applications because it has a regulation range of -1 to 0 bar.

4. Can Danfoss RT pressure switches connect to PLC panels?

Yes, RT pressure switches with SPDT contacts can be wired into PLC digital inputs, relay circuits, alarm panels, or contactor control circuits, provided the wiring and electrical rating are suitable for the application.

5. What does manual reset mean in a pressure switch?

Manual reset means the switch will not automatically return to normal after pressure recovers. Operator action is required. This is useful in safety or fault conditions where automatic restart may not be desirable.

6. Is Danfoss RT 5 suitable for high-pressure applications?

RT 5 has a 4–17 bar regulation range and 22 bar maximum working pressure in the listed Danfoss data, making it suitable for higher pressure applications within its rating. Confirm the final datasheet and exact product code before purchase.

7. What should be checked before buying a Danfoss RT pressure switch?

Check pressure range, differential, reset type, contact rating, process connection, IP rating, media compatibility, working pressure, electrical wiring, mounting, and exact product code.

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Danfoss KP/ KPI Series Pressure Switch Selection Guide for Industrial Pressure Control

Sat, 23 May 2026 08:23:46 +0000

Danfoss KP 35, KP 36 & KPI 38 Pressure Switch Selection Guide

Buy Danfoss products here
A pressure switch is usually noticed only when something stops working.

A pump does not cut off at the right pressure. A compressor trips too late. A boiler or utility line needs pressure protection. A maintenance engineer checks the panel and finds that the old pressure switch has failed, the differential is wrongly selected, or the pressure range does not match the actual process condition.

This is where the Danfoss KP / KPI Series pressure switches become useful for industrial buyers. They are not just on/off switches. They are control and safety devices used to monitor pressure and operate electrical contacts when the pressure reaches a set value.

For Radical TechMart buyers, the key models in this category are:

Danfoss KP 35
Danfoss KP 36
Danfoss KPI 38 / KP 38

The selection should not be done only by model number. The buyer must confirm pressure range, differential, process connection, contact system, media compatibility, enclosure requirement, reset type, and actual application.

What is a Danfoss KP / KPI Pressure Switch?

A Danfoss KP / KPI pressure switch is an electromechanical device that senses pressure and changes an electrical contact when the set pressure point is reached.

In simple words:

Pressure increases or decreases in the system.
The pressure acts on the bellows mechanism inside the switch.
When the pressure reaches the selected cut-in or cut-out point, the electrical contact changes state.
This contact can be used for pump control, compressor control, alarm, trip, interlock, or panel indication.

The Danfoss data shows KP / KPI pressure switches use an SPDT contact system, which is useful for control-panel wiring because one common input can be wired to either normally open or normally closed logic depending on the application. The PDF also explains that the snap-action contact function helps reduce contact bounce and supports accurate changeover at the cut-out point.

Why Correct Pressure Switch Selection Matters

In actual plant conditions, wrong pressure switch selection can create repeated downtime.

A low-range switch used in a higher-pressure system may fail early or become unsafe. A high-range switch used in a low-pressure application may not give accurate switching control. A wrong differential can cause short cycling in pumps or compressors. A wrong enclosure can create problems in dusty or wet installations.

For example, if a pump system needs automatic start-stop control, the differential is very important. If the differential is too narrow, the pump may cycle frequently. If it is too wide, pressure may drop more than acceptable before restart.

This is why the buyer should not ask only, “What is the price of Danfoss KP 35?” A better question is:

“Is Danfoss KP 35 suitable for my pressure range, media, switch logic, enclosure condition, and control panel wiring?”

How Danfoss KP / KPI Pressure Switches Work

The pressure switch works through a mechanical pressure-sensing system and electrical switching mechanism.

When process pressure enters the pressure connection, it acts on the bellows. The bellows movement is transferred to a spring and contact mechanism. Once the set pressure is reached, the contact changes over quickly through a snap-action function.

This matters because industrial systems often have vibration, pressure pulsation, motor starting current, and repeated switching cycles. A stable snap-action contact helps the switch operate more reliably than a slow or weak contact movement.

The Danfoss PDF also defines key terms clearly:

Range setting / set point: pressure range where contact changeover happens.
Differential: difference between contact changeover on rising and falling pressure.
Automatic reset: unit restarts automatically after stop.
Manual reset: unit requires external reset action before operation resumes.
Permissible operating pressure: highest pressure the unit can be continuously exposed to.

Types of Danfoss KP / KPI Series Products Available

Danfoss KP 35

Danfoss KP 35 is suitable when the application needs low-pressure to medium-pressure control. It is commonly selected for systems where pressure monitoring, pump control, compressor protection, or general industrial pressure switching is required.

Best for:

Low to medium pressure control where the pressure point falls within the KP 35 working range.

Why this model makes sense:

KP 35 is useful when the system pressure is not very high but still needs dependable switching for control or protection. For panel builders and maintenance teams, this type is practical when an electrical contact is needed to start, stop, alarm, or interlock equipment based on pressure condition.

Technical points to note:

Product type: Pressure switch
Model: Danfoss KP 35
Setting range: -0.2 to 7.5 bar
Differential: 0.7 to 4.0 bar
Permissible operating pressure: 17 bar
Max. test pressure: 22 bar
Pressure connection: G 1/4 A
Contact material options: silver / gold-plated depending on variant
Variants include IP55 transparent enclosure and stainless steel version options in the PDF listing.

Where it is commonly used:

Pump control panels
Compressor control circuits
HVAC pressure monitoring
Utility pressure control
Process equipment pressure interlock
General industrial automation panels

Selection caution:

Do not select KP 35 only because it is a popular model. Confirm that the normal operating pressure and required switching point fall comfortably inside the -0.2 to 7.5 bar range. Also confirm whether automatic reset, manual reset, enclosure, contact material, and process connection match the site requirement.

Danfoss KP 36

Danfoss KP 36 is suitable when the pressure requirement is higher than KP 35. It is often selected for medium-pressure applications where the switch must operate in a stronger pressure range.

Best for:

Medium-pressure industrial applications where the pressure set point is above the practical range of KP 35.

Why this model makes sense:

KP 36 gives a higher setting range compared to KP 35. This makes it useful for systems where the operating pressure is not low enough for KP 35 but still within a moderate industrial pressure range. In actual maintenance work, selecting KP 36 instead of KP 35 can prevent wrong switching, poor control accuracy, or unsafe over-range use.

Technical points to note:

Product type: Pressure switch
Model: Danfoss KP 36
Setting range: 2.0 to 14.0 bar for common listed variants
Differential: 0.7 to 4.0 bar
Additional listed range option: 4.0 to 12.0 bar with 0.5 to 1.6 bar differential
Permissible operating pressure: 17 bar
Max. test pressure: 22 bar
Pressure connection: G 1/4 A
Contact material options: silver / gold depending on variant
IP55 transparent enclosure and stainless steel version options are shown for selected variants.

Where it is commonly used:

Compressor pressure control
Pump discharge pressure monitoring
HVAC and refrigeration utility lines
Industrial skid control panels
Hydraulic or pneumatic support systems where compatible
Alarm and trip logic in machine panels

Selection caution:

KP 36 should be selected when the process pressure range actually requires it. If the system operates mostly below 2 bar, KP 35 may be more suitable. If the system pressure goes beyond the permissible limit, a higher-rated model should be checked instead.

Danfoss KPI 38

In your store category, KPI 38 can be positioned as the high-pressure option in this KP / KPI product group. It is suitable when the application needs higher pressure switching than KP 35 or KP 36.

Best for:

Higher-pressure control and protection applications where the switching set point is in the 8 to 28 bar range.

Why this model makes sense:

KPI 38 is the model buyers should consider when the application pressure is clearly above the KP 35 and KP 36 selection zone. This makes it useful for high-pressure alarm, cut-out, compressor protection, pump protection, and control-panel interlock functions.

Technical points to note:

Product type: Pressure switch
Model: Danfoss KPI 38
Setting range: 8.0 to 28.0 bar
Differential: 1.8 to 6.0 bar
Permissible operating pressure: 30 bar
Max. test pressure: 30 bar
Pressure connection: G 1/4 A
Contact material: silver in listed variants
Listed code numbers include 060-508166 and 060-541866 depending on variant.

Where it is commonly used:

High-pressure compressor applications
Pump discharge pressure protection
Industrial pressure alarm systems
Process utility pressure monitoring
Machine safety interlock circuits
HVAC and refrigeration pressure control where compatible

Selection caution:

Before selecting KPI 38, confirm the media, pressure pulsation, maximum system pressure, differential requirement, and whether the electrical contact rating is suitable for the connected load. Do not use it as a direct replacement only by physical appearance; always match the pressure range and connection.

Quick Comparison: KP 35 vs KP 36 vs KPI 38

Model	Practical Selection Zone	Setting Range	Differential	Best Use Case
Danfoss KP 35	Low to medium pressure	-0.2 to 7.5 bar	0.7 to 4.0 bar	Pump, compressor, HVAC and general pressure control
Danfoss KP 36	Medium pressure	2.0 to 14.0 bar	0.7 to 4.0 bar	Higher pump/compressor pressure switching than KP 35
Danfoss KPI 38	Higher pressure	8.0 to 28.0 bar	1.8 to 6.0 bar	High-pressure cut-out, alarm, protection and control

Key Selection Factors

1. Pressure Range

First confirm the actual working pressure and required switching pressure.

Do not select the switch at the extreme end of its range if avoidable. A better selection keeps the normal switching point comfortably inside the working range.

2. Differential

Differential controls the gap between cut-in and cut-out.

This matters in pump and compressor applications. Too small a differential may cause frequent cycling. Too large a differential may allow pressure to drop or rise more than the process can tolerate.

3. Reset Type

Automatic reset is useful for normal control. Manual reset is better for safety or fault conditions where the operator must check the system before restarting.

4. Contact Rating

Check the contact rating before connecting the switch directly to a motor starter, relay, contactor, PLC input, alarm circuit, or panel indication. The Danfoss PDF lists SPDT contact systems and contact load data for KP / KPI models.

5. Enclosure Requirement

The PDF mentions IP30 / IP44 / IP55 enclosure possibilities depending on mounting and enclosure arrangement. IP55 requires mounting in a suitable IP55 enclosure.

6. Media Compatibility

Confirm whether the pressure switch is suitable for the actual media: air, water, refrigerant, gas, steam, oil, or other fluid. Do not assume one model suits every media.

7. Process Connection

Confirm G 1/4 A or the required connection thread before ordering. Wrong pressure connection can delay installation and may require unsafe site modification.

Common Applications

Danfoss KP / KPI pressure switches are commonly used in:

Pump control systems
Compressor panels
HVAC systems
Refrigeration support systems
Industrial utility lines
Boiler and pressure monitoring systems
OEM machines
Process automation panels
Alarm and interlock circuits
Maintenance replacement applications

Common Mistakes to Avoid

Mistake	Why It Creates Problems
Selecting only by model number	Same-looking switches may have different ranges and reset types
Ignoring differential	Can cause pump/compressor short cycling
Not checking pressure connection	Installation may not match existing piping
Using KP 35 where KP 36 or KPI 38 is needed	The switch may operate outside the correct range
Ignoring enclosure/IP requirement	Dust, moisture or outdoor exposure can reduce service life
Not confirming contact rating	Electrical load may exceed switch capability
Ignoring media compatibility	Internal parts may not suit the actual fluid
Replacing old switch without checking datasheet	Old installation may already have been wrongly selected

Do This, Not That

Do This	Not This
Select by pressure range and differential	Select only by lowest price
Confirm reset type	Assume every model is automatic reset
Check process connection	Force-fit at site
Match contact rating with panel wiring	Directly connect unknown load
Confirm IP/enclosure requirement	Use standard enclosure in wet/dusty area
Verify media compatibility	Use one model for every application

Quick Selection Checklist

Confirm actual working pressure.
Confirm required cut-in and cut-out pressure.
Select KP 35, KP 36, or KPI 38 based on pressure range.
Check differential requirement.
Confirm automatic or manual reset.
Confirm pressure connection.
Check media compatibility.
Check contact rating and wiring logic.
Confirm enclosure/IP requirement.
Verify datasheet, code number, and availability before purchase.

Why Buy Danfoss KP / KPI Pressure Switches from Radical TechMart?

At Radical TechMart, the focus is not only to supply the product, but to help customers select the right pressure switch for the right application.

This matters because a pressure switch is often part of a larger control system. It may connect to a relay, contactor, PLC input, alarm circuit, compressor panel, pump panel, or machine interlock. A wrong selection can create repeated trips, wrong switching, maintenance difficulty, and downtime.

Radical TechMart can support buyers with:

Danfoss KP / KPI pressure switch selection
Model comparison between KP 35, KP 36 and KPI 38
Datasheet and specification checking
Pricing and availability support
Replacement selection guidance
Industrial pressure control product inquiry support

Final Thoughts

The right Danfoss KP / KPI pressure switch is not selected only by price or model number. It is selected by understanding the pressure range, differential, reset logic, contact rating, process connection, enclosure requirement, and actual field application.

For low to medium pressure applications, Danfoss KP 35 may be suitable. For medium-pressure applications, Danfoss KP 36 becomes a stronger option. For higher-pressure switching, Danfoss KPI 38 should be checked.

In industrial applications, the right instrument is not selected only by price or model number. It is selected by understanding the process, the signal, the environment, and the final control requirement.

FAQs

1. What is the difference between Danfoss KP 35 and KP 36?

Danfoss KP 35 is generally used for lower pressure range applications, while KP 36 is selected for higher pressure requirements. KP 35 is listed with a -0.2 to 7.5 bar setting range, while KP 36 is listed with common variants around 2.0 to 14.0 bar.

2. What is Danfoss KPI 38 used for?

Danfoss KPI 38 / KP 38 is suitable for higher-pressure switching applications. It is commonly selected for compressor, pump, high-pressure alarm, cut-out, and control-panel interlock applications.

3. Can Danfoss KP / KPI pressure switches connect to PLC panels?

Yes, they can be wired into PLC, relay, alarm, or control-panel circuits using their electrical contact output. However, contact rating, wiring logic, and electrical load must be confirmed before installation.

4. What does differential mean in a pressure switch?

Differential is the difference between the pressure point where the switch changes state and the pressure point where it resets. It is important for stable pump and compressor operation.

5. Which is better: automatic reset or manual reset?

Automatic reset is suitable for normal control applications. Manual reset is better for safety or fault conditions where the operator must inspect the system before restarting.

6. Is KP 35 suitable for high-pressure applications?

No, KP 35 should not be selected for high-pressure applications beyond its suitable range. For higher pressure, KP 36 or KPI 38 should be checked depending on the actual pressure requirement.

7. What should I confirm before buying a Danfoss KP / KPI pressure switch?

Confirm pressure range, differential, reset type, pressure connection, media compatibility, contact rating, enclosure/IP requirement, code number, and datasheet before purchase.