Temperature conditions
Tf, holding temperature Th and maximum temperature limit Tm are different parameters. Ambient temperature and heat generated by the equipment must also be considered.
KUNANTENSEIBETTERFUSE / BTT SERIES
Thermal fuses
A non-resettable protective component that interrupts the circuit
when excessive temperature occurs.
BETTERFUSE / BTT01 — THERMAL FUSE
Metal case · Non-resettableØ 4.0 mm
10 / 15ARated current
250V ACRated voltage
21typesTemperature ratings
01PRODUCT OVERVIEW
One interruption.
A protective function.
The BTT series combines a metal case with an organic thermal sensing material. It opens the circuit under specified temperature conditions and cannot reset after operation.
Its role differs from a thermostat used for repeated temperature control. Suitability must be checked against the equipment's temperature, load and installation conditions.
As a Betterfuse sales agent in Japan, Kunantensei supports product information checks and communication with the manufacturer.
—02 / TECHNICAL DATA
Specifications
- Operating type
- Single operation, non-resettable
- Rated current
- 10 A / 15 A
- Rated voltage
- AC 250 V
- Rated functioning temperature Tf
- 73–257°C (21 discrete ratings)
- Body diameter
- Ø 4.0 ± 0.1 mm
- Body length
- 10.3 ± 0.5 mm
- Lead diameter
- Ø 1.0 ± 0.03 mm
Rated functioning temperatures
21 discrete ratings. All listed approvals for the 147°C option are pending in the source.
73°C77°C84°C94°C99°C113°C121°C128°C133°C142°C147°C *152°C157°C167°C172°C184°C192°C216°C229°C240°C257°C
Source: manufacturer OT-BTT-EPS-F/5 and BTT datasheet, dated 22 May 2026 (files marked effective 1 July 2026). Verify approvals, Th and Tm for the selected model and rated current.
—03 / SELECTION GUIDE
Selection goes beyond
a temperature rating.
Consider the application, electrical load and actual installation together.
Electrical conditions
Please provide operating voltage, normal and abnormal current, and load type.
Installation & evaluation
Check the heat transfer path, mounting position and connection method against the manufacturer's specified conditions.
Applications to discussHeating appliances / Coffee makers / Hot-water and warming equipment / Heating assemblies
These application examples are starting points for discussion, not confirmations of suitability or supply experience for a particular device.
See the introduction process—BTT / TEMPERATURE CHARACTERISTICS
Temperature data by rating.
| Tf (°C) | Operating temp. (°C) | Th / 10 A (°C) | Th / 15 A (°C) | Tm (°C) |
|---|---|---|---|---|
| 73 | 69±2 | 58 | 50 | 300 |
| 77 | 74±2 | 62 | 54 | 300 |
| 84 | 80±3 | 69 | 61 | 300 |
| 94 | 91 +3/−2 | 79 | 71 | 300 |
| 99 | 95±2 | 84 | 76 | 300 |
| 113 | 108 +2/−3 | 98 | 90 | 400 |
| 121 | 117±3 | 106 | 98 | 400 |
| 128 | 124±3 | 113 | 105 | 400 |
| 133 | 129 +3/−2 | 118 | 110 | 400 |
| 142 | 140±2 | 127 | 119 | 400 |
| 147 * | 142±2 | 117 | 107 | 400 |
| 152 | 149±2 | 137 | 129 | 400 |
| 157 | 152±2 | 142 | 134 | 400 |
| 167 | 164 +2/−3 | 152 | 144 | 400 |
| 172 | 168±3 | 157 | 149 | 400 |
| 184 | 180±2 | 169 | 161 | 400 |
| 192 | 189±2 | 177 | 169 | 400 |
| 216 | 213±3 | 200 | 193 | 480 |
| 229 | 225±2 | 210 | 205 | 480 |
| 240 | 238±2 | 210 | 205 | 480 |
| 257 | 254±3 | 210 | 205 | 480 |
Th is holding temperature; Tm is maximum temperature limit. The datasheet identifies Th/Tm as PSE parameters, but marks every approval for 147°C (*) as pending. The values in that row do not indicate approval.
Approval coverage varies by temperature. For example, the source marks UL for 94°C and TUV for 184°C as pending. Share the required approval and rating so the relevant documents can be checked.
—PART NUMBER / BTT
Read the BTT part number.
BT · T · 010 · 142 · B
Example BTT010142B: 010 means 10 A (015 means 15 A); 142 means Tf 142°C; B means the normal series with an 18 mm lead. A/B designate 18 mm and C/D designate 43 mm. A/C are special series; B/D are normal series. Check L1 and L2 against the drawing.
Confirm lead length, connection method and operating conditions before ordering. A thermal fuse must not be used as a current fuse.
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