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
Which RESNET/ANSI standard governs water heating energy calculations in HERS ratings?
Answer: ANSI/RESNET/ICC 301-2014 (and subsequent amendments)
ANSI/RESNET/ICC 301 is the core standard that establishes the calculation methodology for HERS ratings, including all water heating energy use calculations.
What impact does replacing a gas storage water heater with a gas tankless (on-demand) water heater typically have on the HERS Index?
Answer: Tankless heaters typically lower the HERS Index by eliminating storage tank standby losses
Gas tankless water heaters eliminate standby heat losses from maintaining a hot storage tank, which typically results in higher efficiency and a lower (better) HERS Index.
A HERS rater evaluating a home with a water heater located in an unconditioned garage should ensure what is accurately modeled?
Answer: That the ambient garage temperature is accounted for, as it affects standby heat losses from the tank
Ambient temperature affects standby heat losses from the water heater tank; a colder unconditioned garage results in greater standby losses than conditioned space installation.
From an energy perspective in HERS ratings, what is the primary purpose of a hot water recirculation system?
Answer: To ensure hot water is quickly available at fixtures, reducing water waste from purging cooled water
Recirculation systems keep hot water ready at fixtures, reducing both the water and the embodied energy wasted purging cooled water from pipes before hot water arrives.
In HERS rating calculations, how is an electric heat pump water heater (HPWH) treated differently from a standard electric resistance water heater?
Answer: The HPWH's higher UEF is credited, resulting in lower modeled water heating energy consumption
The HPWH's significantly higher UEF (typically 2.0–4.0 vs 0.9–0.95 for resistance) is entered into HERS software, directly reducing the modeled energy consumption for water heating.
For HERS verification, what must a rater confirm about an installed water heater to properly credit its efficiency?
Answer: That the unit's UEF or EF rating, model number, and fuel type match what was entered in the HERS software
Raters must verify that the installed water heater's model number, UEF/EF rating, and fuel type match the inputs in the HERS energy model to ensure accurate efficiency credit.
Which of the following hot water distribution improvements would most directly earn a HERS distribution efficiency credit?
Answer: Installing a structured plumbing system with a central manifold and small-diameter individual home runs
Structured plumbing (central manifold with individual small-diameter home runs) minimizes pipe volume and water wasted awaiting hot water, earning recognized HERS distribution efficiency credits.