Thermal Fuses

What are thermal fuses?

Thermal fuses, also called thermal cutoffs, are a safety device used in electrical circuits to provide protection against appliances overheating. Thermal fuses are normally supplied in an axial or radial package, although some thermal fuses are now available as a chip.

How do thermal fuses work?

Thermal fuses work in a similar way to electrical cartridge fuses; when the conditions exceed a certain limit, the circuit will be broken. For thermal fuses, the limit is based on temperature. Thermal fuses typically contain a small pellet within them or have a thin piece of wire which melts at a certain temperature. When the pellet or piece of wire melts, the circuit breaks. This is called 'blowing out' or 'burning out'.

Single-use thermal fuses and resettable thermal fuses

Most thermal fuses are single-use and non-resettable. Once the pellet or piece or wire has melted, the thermal fuse will need replacing before you can operate your appliance again. Resettable fuses are available but tend to have a higher upfront cost than single-use counterparts. For resettable fuses, when the wax pellet within melts, the circuit is broken. However, as the appliance cools, the wax pellet will cool and solidify. This will complete the circuit again and your appliance can be used.

What are thermal fuses used for?

Thermal fuses are used to protect appliances from overheating and can be found in domestic and industrial applications. They are a safety device that helps to prevent fires. For example, thermal fuses can be found in hairdryers, tumble dryers and coffee machines.

What is the difference between functioning temperature and holding temperature?

All thermal fuses have a holding temperature rating and functioning temperature rating. These are key measurements to consider when choosing the right thermal fuse for your application. The holding temperature, normally measured in Celsius, defines what temperature the fuse can operate at continuously without blowing. This is the limit of the safe temperature range for the fuse. The functioning temperature is the lowest temperature rating (also in Celsius) at which the thermal fuse will blow and the circuit will break.

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Description Price Functioning Temperature Holding Temperature Maximum Current Voltage Rating Lead Orientation Series Body Diameter Body Height Body Length Body Width Wire Diameter Wire Length
RS Stock No. 797-6049
Mfr. Part No.SF 090 R
BrandLimitor
TWD39.00
Each (In a Pack of 10)
units
+94°C +79°C 15 A 250 V ac Axial - 4mm 8.5mm - - 1mm 18.5mm
RS Stock No. 797-6030
Mfr. Part No.SF 229 R
BrandLimitor
TWD39.00
Each (In a Pack of 10)
units
+229°C +200°C 15 A 250 V ac Axial - 4mm 8.5mm - - 1mm 18.5mm
RS Stock No. 797-6064
Mfr. Part No.SF 094 R
BrandLimitor
TWD39.00
Each (In a Pack of 10)
units
+99°C +84°C 15 A 250 V ac Axial - 4mm 8.5mm - - 1mm 18.5mm
RS Stock No. 797-6046
Mfr. Part No.SF 070 R
BrandLimitor
TWD39.00
Each (In a Pack of 10)
units
+73°C +58°C 15 A 250 V ac Axial - 4mm 8.5mm - - 1mm 18.5mm
RS Stock No. 712-7284
Mfr. Part No.EYP2BN109
BrandPanasonic
TWD14.30
Each (In a Pack of 10)
units
+114°C +90°C 5 A 250 V ac Axial - 3mm 9mm 9mm - 0.6mm 38mm
RS Stock No. 176-9198
Mfr. Part No.P82 125 05100
BrandLimitor
TWD178.00
Each
units
+125°C - 2.5 A 250 V ac Radial - - 8mm 17.5mm 4mm 0.51mm 100mm
RS Stock No. 176-9148
Mfr. Part No.P82 80 05100
BrandLimitor
TWD178.00
Each
units
+80°C - 2.5 A 250 V ac Radial - - 8mm 17.5mm 4mm 0.51mm 100mm
RS Stock No. 176-9081
Mfr. Part No.P82 45 05100
BrandLimitor
TWD121.00
Each
units
+45°C - 2.5 A 250 V ac Radial - - 8mm 17.5mm 4mm 0.51mm 100mm
RS Stock No. 712-7332
Mfr. Part No.EYP05BE145
BrandPanasonic
TWD12.20
Each (In a Pack of 10)
units
+145°C +125°C 5 A 250 V ac Axial - 1.8mm 5mm 5mm - 0.53mm 38mm
RS Stock No. 176-9097
Mfr. Part No.P82 50 05100
BrandLimitor
TWD200.00
Each
units
+50°C - 2.5 A 250 V ac Radial - - 8mm 17.5mm 4mm 0.51mm 100mm
RS Stock No. 195-8752
Mfr. Part No.NIS6350MT1TXG
TWD17.00
Each (On a Reel of 3000)
units
- - 3 A 5 V - NIS6350 - 0.75mm 3.1mm 3.1mm - -
RS Stock No. 124-5059
Mfr. Part No.A2-5AF
BrandLimitor
TWD43.60
Each (In a Pack of 5)
units
+115°C +75°C 5 A 250 V ac Radial A-5A-F - 8mm 6.6mm 2.6mm 0.6mm -
RS Stock No. 124-5062
Mfr. Part No.A8-5AF
BrandLimitor
TWD36.80
Each (In a Pack of 5)
units
+150°C +105°C 5 A 250 V ac Radial A-5A-F - 8mm 6.6mm 2.6mm 0.6mm -
RS Stock No. 111-7808
Mfr. Part No.SWTC-306-3535
BrandSelco
TWD52.40
Each (In a Pack of 10)
units
+152°C +127°C 10 A 250 V ac Axial SWTC Series 4mm 10mm - - 1mm 35mm
RS Stock No. 111-7813
Mfr. Part No.SWTC-464-3535
BrandSelco
TWD55.50
Each (In a Pack of 10)
units
+240°C +193°C 10 A 250 V ac Axial SWTC Series 4mm 10mm - - 1mm 35mm
RS Stock No. 204-7405
Mfr. Part No.Q82 A 70 05 100
BrandLimitor
TWD209.00
Each
units
+70°C - 2.5 A 250 V ac Radial - - 8mm 17.5mm 4mm 0.51mm 100mm
RS Stock No. 797-6052
Mfr. Part No.SF 167 R
BrandLimitor
TWD34.40
Each (In a Pack of 10)
units
+167°C +153°C 15 A 250 V ac Axial - 4mm 8.5mm - - 1mm 18.5mm
RS Stock No. 204-7382
Mfr. Part No.Q82 A 55 05 100
BrandLimitor
TWD171.00
Each
units
+55°C - 2.5 A 250 V ac Radial - - 8mm 17.5mm 4mm 0.51mm 100mm
RS Stock No. 195-8749
Mfr. Part No.NIS6150MT1TXG
TWD26.90
Each (In a Pack of 50)
units
- - 1 A 5 V - NIS6150 - 0.75mm 3.1mm 3.1mm - -
RS Stock No. 195-8753
Mfr. Part No.NIS6350MT1TXG
TWD23.30
Each (In a Pack of 250)
units
- - 3 A 5 V - NIS6350 - 0.75mm 3.1mm 3.1mm - -