Water Heating Systems Flashcards
7 cards from real HERS practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Water Heating Systems flashcards as text
What does UEF stand for in the context of residential water heaters?
Answer: Uniform Energy Factor
UEF stands for Uniform Energy Factor, the current DOE metric that replaced the Energy Factor (EF) for measuring water heater efficiency.
Which type of water heater typically achieves the highest UEF rating for residential use?
Answer: Heat pump water heater
Heat pump water heaters move heat from ambient air rather than generating it, achieving UEF values of 3.0 or higher — far exceeding other residential water heater types.
According to RESNET/ANSI 301, the HERS reference design water heater efficiency is based on what?
Answer: Federal minimum efficiency standards for the installed fuel type
The HERS reference design uses federal minimum efficiency standards for water heaters matching the rated home's installed fuel type.
How does insulating hot water pipes typically affect a HERS rating?
Answer: It lowers the HERS Index by reducing heat loss in the distribution system
Insulating hot water pipes reduces standby heat losses in the distribution system, which lowers the HERS Index, indicating better energy performance.
What is drain water heat recovery (DWHR)?
Answer: A device that captures heat from draining shower water to preheat incoming cold water
DWHR devices capture thermal energy from warm drain water (typically from showers) and use it to preheat cold water entering the water heater, reducing energy consumption.
In HERS rating calculations, on what is the daily domestic hot water consumption estimate primarily based?
Answer: Number of bedrooms in the home
RESNET/ANSI 301 uses the number of bedrooms as a standardized proxy for occupancy to calculate daily hot water consumption in HERS ratings.
Which hot water distribution system configuration typically results in the best delivery efficiency in a HERS rating?
Answer: Compact distribution system with short runs and small-diameter pipes
Compact distribution systems minimize the pipe volume between the water heater and fixtures, reducing both wait time for hot water and water wasted while purging cooled water.