A snap-action two-temperature valve provides rapid response to temperature changes in HVAC systems. It is commonly used with multiple evaporator systems.

A snap-action two-temperature valve provides rapid response to temperature changes in HVAC systems. It is commonly used with multiple evaporator systems.

• A. They are used with single evaporator systems
• B. They require a positive pressure to operate
• C. They are commonly used with multiple evaporator systems
• D. They do not respond to temperature changes

Answer: (C)

Two-temperature snap-action valves are driven by a temperature-sensing bulb that causes the valve to snap between two positions as soon as a setpoint is reached. This rapid switching makes them particularly useful in systems with multiple evaporators, where you want to quickly direct refrigerant to the evaporator that’s calling for cooling and prevent sluggish responses across zones. In a single-evaporator setup there’s typically no need to swap flow between evaporators, so the advantage of fast, discrete switching is less relevant. The valve operates on temperature changes at the sensing bulb; while system pressures influence overall operation, it’s the temperature signal—not a required positive pressure—that triggers the snap action.

Two-temperature snap-action valves are driven by a temperature-sensing bulb that causes the valve to snap between two positions as soon as a setpoint is reached. This rapid switching makes them particularly useful in systems with multiple evaporators, where you want to quickly direct refrigerant to the evaporator that’s calling for cooling and prevent sluggish responses across zones. In a single-evaporator setup there’s typically no need to swap flow between evaporators, so the advantage of fast, discrete switching is less relevant. The valve operates on temperature changes at the sensing bulb; while system pressures influence overall operation, it’s the temperature signal—not a required positive pressure—that triggers the snap action.