Compared to R22 systems, the flow rate of a thermostatic expansion valve (TEV) in a 410A system is approximately what?

Compared to R22 systems, the flow rate of a thermostatic expansion valve (TEV) in a 410A system is approximately what?

• A. Approximately 15% greater
• B. Approximately 15% less
• C. Approximately the same
• D. Approximately 30% greater

Answer: (A)

TEVs meter refrigerant to the evaporator, and their flow depends on the refrigerant’s density and the pressure forces across the valve. In a 410A system, pressures are higher than in an R22 system, so the liquid entering the valve is denser. To achieve the same cooling and maintain proper superheat, the valve must pass more mass flow. This tendency to higher flow for 410A is typically about 15% greater than for R22 systems. So the best choice reflects a modest increase in flow to accommodate the higher pressure and density of 410A. The other options either imply less flow, no change, or too large a difference, which doesn’t align with how TEVs are adjusted for 410A.

TEVs meter refrigerant to the evaporator, and their flow depends on the refrigerant’s density and the pressure forces across the valve. In a 410A system, pressures are higher than in an R22 system, so the liquid entering the valve is denser. To achieve the same cooling and maintain proper superheat, the valve must pass more mass flow. This tendency to higher flow for 410A is typically about 15% greater than for R22 systems. So the best choice reflects a modest increase in flow to accommodate the higher pressure and density of 410A. The other options either imply less flow, no change, or too large a difference, which doesn’t align with how TEVs are adjusted for 410A.