Regarding servicing air cooled condensers, the correct pressure may be determined as follows. first, add ___ degrees to 35 degrees F.

• A. 30
• B. 10
• C. 50
• D. 5

Answer: (A)

For air‑cooled condensers, a quick way to estimate the high‑side pressure is to link condensing temperature to outdoor conditions with a simple add‑on rule. Start from a baseline of 35 °F and add a fixed amount to approximate the condensing temperature you’ll use on the pressure–temperature chart. The standard value used here is 30 degrees, giving about 65 °F as the condensing temperature to reference on the P–T chart. Once you have that estimated condensing temperature, you look up the corresponding high‑side pressure (psig) for the refrigerant being serviced. This Rule of Thumb lets you quickly check whether pressures are in a reasonable range for the current outdoor temperature.

Adding a smaller amount would underpredict head pressure on warmer days, while adding more than 30 would push the estimate too high and become less accurate in practice. The 30‑degree addition provides a balanced, commonly used quick estimate.