What device acts as a safety shutoff by responding to temperature changes to prevent equipment overheating in HVAC systems?

What device acts as a safety shutoff by responding to temperature changes to prevent equipment overheating in HVAC systems?

• A. circuit breaker
• B. limit control
• C. thermostat
• D. pressure relief valve

Answer: (B)

Limit controls act as temperature-sensitive safety switches that shut off heating when the system overheats. They monitor the temperature near the heat exchanger or in the discharge path, and when a preset high limit is reached, they open the electrical circuit to the burner or other heat source. This stops heat production and prevents damage or fire from excessive temperatures. Some limit controls reset automatically after cooling, while others require manual resetting. This role is distinct from a circuit breaker, which protects against electrical overload rather than high temperature; a thermostat, which regulates operation to reach a setpoint for comfort, not as a safety cutoff; and a pressure relief valve, which protects against overpressure rather than overheating.

Limit controls act as temperature-sensitive safety switches that shut off heating when the system overheats. They monitor the temperature near the heat exchanger or in the discharge path, and when a preset high limit is reached, they open the electrical circuit to the burner or other heat source. This stops heat production and prevents damage or fire from excessive temperatures. Some limit controls reset automatically after cooling, while others require manual resetting. This role is distinct from a circuit breaker, which protects against electrical overload rather than high temperature; a thermostat, which regulates operation to reach a setpoint for comfort, not as a safety cutoff; and a pressure relief valve, which protects against overpressure rather than overheating.