What happens after the hot contacts close in the burner safety switch?

• A. The safety switch heater remains energized
• B. The safety switch heater is taken out of the circuit and the burner continues to operate
• C. The burner shuts off immediately
• D. The flame goes out

Answer: (B)

When the burner safety switch is in action, a small heater inside it is used to heat a bi-metal or similar element and close two hot contacts, creating a hold-in circuit that lets the burner start and keep running. After those contacts have closed, that heater is taken out of the circuit, and the closed contacts stay engaged to keep the burner energized even though the heater isn’t actively heating anymore. This allows the burner to continue operating safely, as long as flame sensing indicates a valid flame. If the flame goes out, the safety switch will open, cutting off the gas to stop the burner.