Name the regulator used in a combination gas valve to reduce the building gas pressure to the correct burner working pressure.

The correct answer is the appliance regulator. This device is specifically designed to reduce the gas pressure from the supply line to the lower pressure used by the appliances, ensuring they operate safely and efficiently at their required working pressure. The appliance regulator is essentially tailored for specific gas-burning appliances and is integral to providing precise and stable gas pressure control, which is crucial for the safe operation of gas appliances such as furnaces and water heaters.

This regulator actively manages the delivery of gas by compensating for fluctuations in supply pressure, thereby maintaining a steady pressure at the appliance's inlet. The design considers both the specific requirements of the appliance and the characteristics of the gas being used, ensuring optimal performance.