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Klixon Probe Packages

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Here’s a breakdown of our part numbering system for probe packages:

Field 1
(or 21546, 21544, 21547, or 21550)
Basic package describes general physical appearance and basic thermostat incorporated into device
Field 2
Probe length times 2 (probe length is the length in inches from bottom of the hex to bottom of the device)
Field 3
Operating characteristics, assigned consecutively (Sensata will assign this number at the time your order is taken)
Field 4
For wire leads, this is the length of wire in 6 inch increments (for 6" it would be 1, for 12" it would be 2, for 18" it would be 3, etc.). For connectors, contact Sensata Technologies for this code.

So, a ¾" - 16 thread with connector (see "Standard Part Numbers and Configurations" at right) with probe length of 3" and with an 18" wire lead would be numbered: 21546-06-xxx-03.

Site Updated February 16, 2018

* * * Sensata > Products > Klixon Brand > Thermostats > Precision Thermostats >

Klixon® Thermostat Probe Packages: Narrow Differential Control

This snap–acting, probe–type thermal switch incorporates the reliable Klixon® 4286 thermostat.

These thermostat probes accurately open and close within a narrow 2° to 8° F differential providing close temperature control in critical applications.

For more information, see the page of free drawings available or download the data sheet (file type: PDF).


The standard narrow differential probe utilizes silver contacts. Gold plated contacts can be furnished to assure reliable circuit switching under low wattage conditions. (See second table below.)

Contact Ratings (Resistive) Based on standard differential
125 VAC
Life Cycles
2.0 Amps
2.0 Amps

Gold Contact Ratings (Resistive) Gold-plated contacts are not suitable for higher loads.
500 mA and below
115 VAC
200 mA and below
230 VAC
100 mA and below

Contact Resistance
0.100 ohms per MIL-STD-202, Method 307
Dielectric Strength
1250 VAC, rms, 60 cycles for 1 minute, per MIL-STD-202, Method 301
Salt Spray Resistance
Per MIL-STD-202, Method 101, Condition B, 5% Solution
Ambient Temperature Range
-65°F to 400°F (-53.9°C to 204.4°C)
Maximum ambient exposure should be limited to 100°F above operating temperature for close on rise devices or 100°F below the operating temperature for open on rise devices.
Operating Temperature Range
0°F to +275°F, (-17.8°C to 135°C)

The standard operating temperature ranges, differential and tolerances are shown in the table below, but can be customized to meet your specific requirements.

Operating Temp.
Closing Temperature Tolerance*
0 to 250°F
(-117.8 to 121.1°C)
2 to 5°F
(1.1 to 2.8°C)
+/- 5°F
(+/- 2.8°C)
251 to 275°F
(121.7 to 135°C)
3 to 8°F
(1.7 to 4.4°C)
+/- 6°F
(+/- 3.4°C)
* Tolerances are based on precision factory calibration and test equipment. Customers checking tolerances should allow for differences in test equipment of ±1°F.


Standard narrow differential probe packages are comprised of the following physical features, but many other variants are available to meet your needs.

PLEASE NOTE: The orientation of the connector with respect to the package body is not controlled.

Configuration Options - Custom configurations are available
Probe Body Thread Sizes
Standard lengths are available in ½" increments, from 1.5" to 6". Standard probe bodies are available with the following thread sizes:
¾" - 16
½" - 14 NPT
Standard connector is a Sealtron B8002G-10SL-4P-F (or equivalent)
Standard wire leads are AWG #18 stranded wire with white or black Teflon* insulation (per MIL-W-22759) (Teflon is a trademark of E. I. Dupont de Namers and Co.)
The standard material is stainless steel
Other styles are available, as well as custom designs

Standard Part Numbers and Configurations - Many other styles are available Also, see free drawings available for download.
½" pipe thread with leads
¾" - 16 thread with connector
¾" - 16 thread with leads
½" pipe thread with connector
* * *
Miniature Thermostats

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