How do you convert PSIG to PSIA?

To convert PSIG (pounds per square inch gauge) to PSIA (pounds per square inch absolute), it is essential to understand the relationship between gauge pressure and absolute pressure. PSIG measures pressure relative to atmospheric pressure, meaning it does not include the weight of the atmosphere's pressure above the measurement point. In contrast, PSIA accounts for this atmospheric pressure.

The atmospheric pressure at sea level is approximately 14.7 psi. Therefore, to convert a gauge pressure reading to an absolute pressure reading, you add this atmospheric pressure to the PSIG value. For example, if you have a PSIG measurement of 30 psi, the PSIA would be calculated as follows: 30 PSI + 14.7 PSI = 44.7 PSIA. This relationship holds true regardless of the specific PSIG value, thus confirming the correct approach to conversion.

This understanding of pressure types is crucial in HVAC applications for ensuring accurate measurements and calculations related to system performance and safety. The other potential methods involving subtraction, multiplication, or division of the PSIG value by 14.7 would not yield the proper absolute pressure calculation, as they do not accurately reflect the addition of atmospheric pressure.