Arkansas HVACR NewsMagazine November 2024

HVACR NewsMagazine November 2024

Tech News

air in the space is <60% and the supply RH is 85 – 100%?

It ’ s All Relative

Humidity

Florida's got a lot of great qualities: some pretty neat wildlife, beaches all around, and theme parks. On the flip side, Florida also has hurricanes and a lot of humidity. As much of a pain as it might be for residents and contractors alike, humidity is one of my favorite topics. We see relative humidity (RH) levels in the 70 – 80% range consistently on extremely hot, muggy Florida days. However, the cooler nights feel a lot less muggy but often have RH values approaching 100%. What gives? It doesn't feel more humid, but the RH is higher — why? It's the same reason why the supply relative humidity can be near 100%, even though the HVAC system is supposed to dehumidify the air. In this tech tip, we'll talk a bit about how the same relative humidity level can feel so much different at different temperatures, and we'll answer the age-old question: If the HVAC unit is supposed to remove moisture from the air, how come the relative humidity of the This article was furnished by Brian Orr and HVAC School For Techs by Techs. It is an amazing article on a subject that is affecting us more than ever before. We appreciate them sharing their excellent articles and encourage our readers to subscribe to their site at https://hvacrschool.com/start/

The Two Types of Humidity

We measure relative humidity (RH) in the work we do, as do meteorologists and weather reporters. RH is the ratio of the moisture in the air to the amount of moisture the air can hold. It is NOT the total amount of moisture in the air. The total amount of moisture in the air is absolute humidity , and we measure it in grains. We can see how many grains there are if we plot the temperature and relative humidity on a psychrometric chart. (Use the dry-bulb temperature horizontally and RH vertically; the grains of moisture will be visible on the right-hand side.)