What cold inlet and rise temperatures are commonly used when selecting a hot water heater?

When selecting a hot water heater, the cold inlet and rise temperatures are critical for determining the unit's efficiency and capacity to meet hot water demand. The commonly used cold inlet temperature is about 40 degrees Fahrenheit, as this reflects average ground and surface water temperatures in many regions. The temperature rise refers to the difference between the cold inlet water temperature and the desired output temperature of the hot water. Typically, a rise of around 100 degrees Fahrenheit is standard, aligning with the usual output temperature expectations in residential and commercial settings, which often target around 140 degrees Fahrenheit for hot water.

Option B aligns with industry practices by using a cold inlet temperature of 40 degrees Fahrenheit combined with a rise of 100 degrees Fahrenheit. This selection provides a balanced representation of typical conditions and is practical for sizing and selecting appropriate hot water heaters for most applications.