Thermocouple Extension Wire


Standard Limits of error | Insulated | Stranded or solid

Thermocouple Extension Wire is used to complete the thermocouple circuit from the thermocouple element to the temperature instrument. Note that extension grade wire should not be used to make thermocouple elements. Extension wires can be divided into two categories. Category 1 extension wire are made with conductors which are the same material as the thermocouple elements. Category 2 extension wire are made from conductors which are different from the thermocouple elements. The base metal thermocouples are used with a Category 1 extension wire. Noble metal thermocouples and some of the non standardized thermocouples are used with Category 2 extension wires.

The extension wire and thermocouple wire must be of the same calibration type to maintain the accuracy of the thermocouple sensor. The polarity of each set of wires must also be maintained during installation in order for the thermocouple circuit to function properly. The RED wire is always the NEGATIVE leg of the the extension wire and thermocouple wire. The outer jacket of extension grade thermocouple wire is also color coded to help with the identification and installation.

Thermocouple extension wire which will be subject to frequent flexing, should have stranded conductors to prevent fatigue and later potential wire failure. For most typical installations, a 20 gauge, solid conductor with PVC insulation (20KX-PP) is an excellent choice.


  • Standard Limits of Error
  • 20 to 14 Wire Gauge Sizes
  • Stranded or Solid Conductors
  • Thermocouple Types, B, E, C, J, K, N, T, R, and S
  • High Temperature Insulations
  • Moisture Resistant Insulations
  • Stainless Steel or Inconel 600 Overbraids
Thermocouple Extension Wire | Type KX
Mgo Thermocouples With Male Plug
Part Number
Wire Gauge

Wire Form

Insulation Max Temp Lbs / 1000 Ft. Wire Sizes Inches
14KX-PP 14 Solid Polyvinyl Plastic 200°F 34.5 5.6 x 3.8
16KX-GG 16 Solid Fibre Glass, Impregnated 400°F 17.9 3.8 x 2.2
16KX-GG-S 16 Stranded Fibre Glass, Impregnated 400°F 20.8 4.1 x 2.5
16KX-PP 16 Solid Polyvinyl Plastic 220°F 25.0 5.1 x 3.3
16KX-TT 16 Solid Teflon TFE (Fused Tape) 400°F 25.0 4.1 x 2.5
16KX-TT-S 16 Stranded Teflon TFE (Fused Tape) 400°F 27.8 4.8 x 2.5
20KX-GG* 20 Solid Fibre Glass, Impregnated 900°F 7.7 2.3 x 1.5
20KX-PP 20 Solid Polyvinyl Plastic 220°F 12.5 4.1 x 2.5
20KX-PP-S 20 Stranded Polyvinyl Plastic 220°F 14.0 4.7 x 2.7
20KX-PP-TW-SD 20 Stranded Polyvinyl Plastic 220°F 16.0 4.32 x 4.32
20K-TT-EX* 20 Solid Teflon FEP (Extruded) 400°F 11.0 3.1 x 1.8

Color Code - Yellow (Positive, Non-magnetic, Ni, 10% Cr) and Red (Negative, Magnetic, Ni, 5% Al, Si)
Outer Jacket - Brown, with Yellow tracer.
*Thermocouple Grade has Overall Brown and Yellow Tracer Outer Jacket