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
A heat pump water heater (HPWH) will operate most efficiently when installed in which location?
Answer: An unconditioned space such as a garage with sufficient air volume
HPWHs need access to a large volume of ambient air to extract heat efficiently; unconditioned spaces like garages provide a heat source without penalizing conditioned space HVAC loads.
For HERS purposes, what does the 'hot water distribution system efficiency' credit account for?
Answer: Energy losses from pipe heat dissipation and water wasted waiting for hot water to arrive
Hot water distribution efficiency credits in HERS account for both thermal losses from pipes and water wasted waiting for hot water to arrive at fixtures.
What credit does a solar water heating system receive in a HERS rating?
Answer: Credit based on the calculated solar fraction and system efficiency per RESNET standards
Solar water heating systems receive HERS credit based on the calculated solar fraction and system efficiency as specified in RESNET/ANSI 301 standards.
Which of the following best describes a 'compact' hot water distribution system as recognized in HERS ratings?
Answer: A system where total pipe volume from water heater to all fixtures is minimized using small-diameter pipes and short runs
Compact distribution systems minimize the pipe volume between the water heater and fixtures, reducing the amount of cooled water that must be purged before hot water arrives.
Compared to a continuous recirculation system, how does a demand-controlled recirculation system affect energy use in HERS?
Answer: Demand-controlled systems reduce standby heat losses by running only when activated by occupant demand
Demand-controlled recirculation systems activate only when hot water is requested, significantly reducing standby circulation losses compared to continuous or timer-based systems.
In HERS energy modeling, how is incoming cold water (mains) temperature typically determined?
Answer: Location-dependent values based on ground temperature data
RESNET/ANSI 301 uses location-specific mains water temperatures based on geographic ground temperature data, as cold water temperatures vary significantly across US climate zones.
What is the primary advantage of a structured plumbing (central manifold) system over a traditional trunk-and-branch distribution system in HERS?
Answer: Reduced pipe volume per fixture, minimizing water waste and improving distribution efficiency
Structured plumbing systems use individual small-diameter home runs from a central manifold to each fixture, minimizing total pipe volume and reducing water wasted waiting for hot water.