Which condition would you expect from an overcharged refrigerant in a capillary tube system?

Which condition would you expect from an overcharged refrigerant in a capillary tube system?

• A. Low suction pressure and low discharge pressure
• B. High suction pressure and lower than normal discharge pressure
• C. High suction pressure and high discharge pressure
• D. Low suction pressure and high discharge pressure

Answer: (C)

When there’s more refrigerant in a capillary tube system than the system can effectively use, extra liquid circulates through the cycle. The capillary tube is a fixed restriction, so the added refrigerant increases the amount that must be compressed and pushed through the condenser. That makes the condenser work harder, raising the discharge (high-side) pressure. At the same time, more refrigerant entering the evaporator raises the amount of vapor that is produced, increasing the evaporating pressure on the low side, which shows up as a higher suction pressure. So both sides rise: high suction pressure and high discharge pressure. If the system were undercharged, you’d expect both pressures to be low. If only the discharge pressure were high, that would point to a different issue (like condenser performance) without the accompanying rise on the low side. The combination of elevated pressures on both sides fits the overcharged, capillary-tube scenario.

When there’s more refrigerant in a capillary tube system than the system can effectively use, extra liquid circulates through the cycle. The capillary tube is a fixed restriction, so the added refrigerant increases the amount that must be compressed and pushed through the condenser. That makes the condenser work harder, raising the discharge (high-side) pressure. At the same time, more refrigerant entering the evaporator raises the amount of vapor that is produced, increasing the evaporating pressure on the low side, which shows up as a higher suction pressure. So both sides rise: high suction pressure and high discharge pressure.

If the system were undercharged, you’d expect both pressures to be low. If only the discharge pressure were high, that would point to a different issue (like condenser performance) without the accompanying rise on the low side. The combination of elevated pressures on both sides fits the overcharged, capillary-tube scenario.