Water Heating Systems Flashcards
6 cards from real 306A practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Water Heating Systems flashcards as text
What is a 'heat pump' water heater?
Answer: A water heater that extracts heat from ambient air and transfers it to the water, operating like a refrigerator in reverse
A heat pump water heater uses a refrigeration cycle to extract heat energy from the surrounding air and transfer it to the water in the tank. It is 2 to 3 times more efficient than a conventional electric resistance heater.
What is the energy factor (EF) or uniform energy factor (UEF) used to measure in water heaters?
Answer: The overall efficiency of the heater, accounting for recovery efficiency, standby losses, and cycling losses
The energy factor (or the newer uniform energy factor) measures the overall efficiency of a water heater by accounting for how efficiently it heats water (recovery), how much heat it loses from the stored water (standby), and the energy consumed during cycling on and off.
When installing a solar water heating system, what is the purpose of the backup heating element?
Answer: To provide supplemental heating when solar energy is insufficient, such as during cloudy days or high demand
The backup heating element (electric, gas, or a conventional water heater in series) ensures hot water availability when solar energy cannot meet the demand, such as during extended cloudy periods, winter months, or peak usage times.
What is the purpose of a mixing valve at the water heater outlet?
Answer: To blend the hot water stored at 60°C with cold water to deliver a safe temperature (typically 49°C) to fixtures
A thermostatic mixing valve at the water heater outlet blends the 60°C stored water (maintained at this temperature to kill Legionella) with cold water to deliver tempered water at a safe 49°C to fixtures, preventing scald injuries.
What is 'first-hour rating' (FHR) for a storage water heater?
Answer: The number of litres of hot water a fully heated tank can deliver in the first hour, combining stored volume and recovery capacity
The first-hour rating represents the total litres of hot water the heater can deliver starting with a fully heated tank, combining the stored hot water with the water heated during that hour (recovery). This is the best indicator of the heater's ability to meet peak demand.
What safety device prevents a gas water heater from operating if the flue is blocked?
Answer: A spill switch or blocked vent safety shutoff that detects exhaust gas spillage
A spill switch (or blocked vent safety device) detects when combustion gases are spilling from the draft hood instead of going up the flue. It shuts off the gas supply to prevent carbon monoxide from accumulating in the living space.