Hi all!
I wanted to follow up on a great discussion we had this past Sunday, 11/17, during the PDD HVAC, Electrical, and Plumbing workshop, regarding question #4 in the mechanical section.
The question asks you to find the cooling load for a building in Denver, CO using the provided Denver Climate data. This is a great, but somewhat tricky, question because if you read too quickly, you may miss a key word. It’s easy to assume that because the location is Denver, CO, you’d want to find the heating load, because Denver is a colder location. But the second to last word is critical because it says to calculate the annual cooling load. It’s also important to pay attention to the hint about substituting the CDD for HDD. Using the annual HDD will not get you the right answer. Luckily, the actual exam is multiple choice so if you use HDD and get an answer that’s way off base, it will encourage you to reread the question and realize that you need to use CDD.
As a refresher:
HDD “measures how many days a building would need to be heated by 1 degree to meet its heating needs. HDD is calculated by subtracting the mean daily temperature from 65°F for each day of the year, and then adding up the results. For example, a day with a temperature of 55°F is worth 10 HDD because it’s 10°F below 65°F.”
CDD “measures how many days a building would need to be cooled by 1 degree to meet its cooling needs. CDD is calculated by subtracting 65°F from the mean daily temperature for each day of the year, and then adding up the results. For example, a day with a temperature of 80°F is worth 15 CDD because it’s 15°F above 65°F.”
Good luck studying!