Which component triggers heat sensing devices at 160 ± 3 °F?

Which component triggers heat sensing devices at 160 ± 3 °F?

• A. Thermostatic switch
• B. Fusible link
• C. Bi-metal strip
• D. Capacitive sensor

Answer: (B)

A fusible link is used because it is a metal element designed to melt at a precise temperature. When the ambient reaches 160 ± 3 °F, the fusible link melts, triggering the heat-sensing device reliably at that specific temperature. This provides a one-shot, well-defined temperature threshold, which is ideal for heat-triggered safety devices. In contrast, a thermostatic switch relies on a bi-metal strip to open or close a circuit at a set temperature and can reset after cooling, which isn’t the same kind of fixed, melt-based trigger. The bi-metal strip is the sensing element inside that switch, not the trigger itself. A capacitive sensor measures changes in capacitance and isn’t used to trigger at a fixed heat threshold.

A fusible link is used because it is a metal element designed to melt at a precise temperature. When the ambient reaches 160 ± 3 °F, the fusible link melts, triggering the heat-sensing device reliably at that specific temperature. This provides a one-shot, well-defined temperature threshold, which is ideal for heat-triggered safety devices.

In contrast, a thermostatic switch relies on a bi-metal strip to open or close a circuit at a set temperature and can reset after cooling, which isn’t the same kind of fixed, melt-based trigger. The bi-metal strip is the sensing element inside that switch, not the trigger itself. A capacitive sensor measures changes in capacitance and isn’t used to trigger at a fixed heat threshold.