Danfoss KP switches are used for regulating,
monitoring and alarm systems in the industry.
They provide automatic limit protection or
manual reset limit protection for pressure
systems. Can be used with steam, air, gaseous
and liquid media.
The pressure switches are tted with singlepole changeover switch (SPDT). The position of
the switch depends on the setting of the
pressure switch and the pressure in the
connector.
KP Thermostats
KP thermostats are temperature-operated
electric circuit breakers. The thermostats are
tted with single-pole changeover switch
(SPDT)
The position of the switch depends on the
thermostat setting and sensor temperature. A
KP thermostat can be connected and switch to
single-phase alternating current motors of up
to 2 kW.
AI209986438809en-000602
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Key sketch of KP pressure switch
Simplied drawing of KP pressure switch without front cover and scale.
Version with manual reset.
Range setting spindle
Dierential setting spindle
Main arm
Main spring
Dierential spring
Bellows
Pressure connector
Contact system
Switch terminals
Ground terminal
Cable entry: ½ in female NPSM
Tumbler
Locking screw
Manual reset
Distance plate
Pressure switches and thermostats, Type KP
Features
• Wide regulating range
• Small dimensions
⁃ Space-saving, easy to install in panels
• Shock and impact resistant
• Ultra-short bounce time. Limits wear to an absolute minimum and increases reliability
• Snap action electrical contacts minimize chatter, bounce, and wear, and ensure long term electrical and
mechanical reliability
• Electrical connection from front of the unit. Makes rack mounting easier and also saves space
• Suitable for alternating current and direct current
• Screwed wiring, makes rewiring easy
• Manual trip allows electrical function test without tools
• Versions with automatic and manual reset available
Functions
Pressure switches
Table 1: Design and function
The contact system of KP switches has a snap-action function and the bellows moves only when cut-in or cut-out
set point is reached.
Terminals 1 – 4 close high and open low
Terminals 1 – 2 can be used as low temperature alarm
Low pressure cut-out
Terminals 1 – 2 open high and close low
Terminals 1 – 4 can be used as high temperature alarm
High pressure cut-out
Pressure switches and thermostats, Type KP
Thermostats
Table 6: Contact system and application
Setting
Pressure switches
Cut-in and cut-out pressures of the system should always be checked with an accurate pressure gauge.
Pressure setting for switches with automatic reset.
Set the cut-out pressure on RANGE scale and dierential on DIFF scale.
NOTE:
Restart pressure is equal to cut-out pressure minus dierential value.
Pressure switches with manual reset
Set the cut-out pressure on the RANGE scale. Pressure limiters can be manually reset by pressing reset button when
the pressure is equal to the cut-out pressure minus xed value of the dierential.
Thermostats
Thermostats with automatic reset
Set the cut-out temperature on the RANGE scale and dierential on the DIFF scale. Restart temperature is equal to
the cut-out temperature minus dierential value.
NOTE:
The dierential scale is only a reference. The exact value of distances on the scale depends on where in its range the
switch cut-in is set. Use the dierential scale as a guide, and if precise function is required, establish the dierential
setting by comparing function with an accurate thermometer in the controlled zone.
Thermostats with manual reset
Set the cut-out temperature on the range scale.
The dierential is xed. Restart the system by pressing the reset button after the temperature of the sensor falls to a
value equal to the range scale setting minus the xeddierential.
Terminology
Pressure switches
Set point
A predetermined value to which a switch is adjusted and at which it performs its intended function.
Reset:
1.
Manual reset: Units with manual reset can only be restored to operational mode by activation of the external
reset button.
2.
Automatic reset: Units with automatic reset is restored to operational mode automatically.
Maximum working pressure
The maximum permissible pressure for safe functioning of a heating system or any of its part.
Snap function
A specic contact force is maintained until snap is initiated. The time over which contact force reaches zero is a few
milliseconds; therefore, contact bounce cannot occur as a result, for example, of slight vibrations before cut-out. The
snap-action contact system will continue to function even when micro-welds are created between the contacts
during cut-in. The force created to separate the contacts is strong, and instantly shears o all contact surface welds
that have been created as the result of cut-in action. These design features ensure that the cut-out point of the KP
switch remains very accurate and completely independent of the magnitude of the current load.
FLA - Motor Full Load Amperes
FLA is the largest current that a motor or other device is designed to carry at rated voltage and other specic
conditions. Also often called current at rated conditions.
LRA - Locked Rotor Amperes
LRA is the current in amperes drawn by an electric motor with the shaft or rotor immobilized.
Thermostats
Dierential
The dierential is the dierence between the cut-in and cut-out temperatures.
The dierential is necessary for satisfactory automatic operation of the controlled system. Mechanical dierential
(intrinsic dierential). The mechanical dierential is the dierential set by the dierential spindle.
Reset:
1.
Manual reset: Units with manual reset can only be restarted after activation of the reset button. On max reset
units the set value is equal to cut-out value for rising temperature.
2.
Automatic reset: Units with automatic reset is restored to operational mode automatically.
Snap function
A specic contact force is maintained until snap is initiated. The time over which contact force reaches zero is a few
milliseconds; therefore, contact bounce cannot occur as a result, for example, of slight vibrations before cut-out. The
snap-action contact system will continue to function even when micro-welds are created between the contacts
during cut-in. The force created to separate the contacts is strong, and instantly shears o all contact surface welds
that have been created as the result of cut-in action. These design features ensure that the cut-out point of the KP
switch remains very accurate and completely independent of the magnitude of the current load.
FLA - Motor Full Load Amperes
FLA is the largest current that a motor or other device is designed to carry at rated voltage and other specic
conditions. Also often called current at rated conditions.
LRA - Locked Rotor Amperes
LRA is the current in amperes drawn by an electric motor with the shaft or rotor immobilized.
Thermostat charge
Figure 1: Thermostat charge
Sensors with adsorption charges contain a superheated gas together with a solid having a large adsorption surface.
The sensor can be placed in zones that are warmer or colder than the switch housing and capillary tube, but
variations of more than 70 °F may inuence scale accuracy.
Brackets with mounting screws and
washers for pressure switches and
thermostats
Angle bracket
4 screws 10–32 UNC + 4 washers
060-105366
Top cover for pressure switches and
thermostats
When the bracket is mounted on the back plate of the housing, the grade of enclosure of the KP switch is IP44. Top cover
covers the setting spindles.
060-109766
Document type
Approvals Authority
Electrical - Safety
Certicate
CCC
Manufacturer Declaration
EAC
EU Declaration
CE/ LVD
Food and Health - Performance
Certicate
PZH
Marine safety
certicate
RINA
Marine Approval
RMRS
Manufacturer Declaration
RoHS China
Electrical - Safety
Certicate
FM
Electrical - Safety
Certicate
UL
Pressure switches and thermostats, Type KP
Ordering
Pressure switches
Table 8: Ordering
Thermostats
Table 9: Ordering
Table 10: Accessories
Certicates, declarations, and approvals
The list contains all certicates, declarations, and approvals for this product type. Individual code number may have
some or all of these approvals, and certain local approvals may not appear on the list.
Some approvals may change over time. You can check the most current status at danfoss.com or contact your local
Danfoss representative if you have any questions.
Table 11: Certicates, declarations, and approvals
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