Hydronic Heating Systems Flashcards
7 cards from real HVAC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Hydronic Heating Systems flashcards as text
What is the function of a differential pressure bypass valve in a variable-flow hydronic system?
Answer: To maintain minimum flow through the boiler when zone valves close
The differential pressure bypass valve opens to create a short-circuit path for flow when zone valves close, ensuring the boiler and pump always have adequate minimum flow.
In radiant floor heating, what is the typical maximum supply water temperature to avoid damaging flooring materials?
Answer: 120°F
Radiant floor systems are typically limited to supply water temperatures of 120°F or less to protect flooring materials and maintain comfortable floor surface temperatures.
A hydronic boiler's aquastat controls which function?
Answer: Boiler water temperature by cycling the burner
The aquastat is a water temperature sensing control that cycles the boiler burner on and off to maintain the boiler water within a set temperature range.
What does outdoor reset control do in a hydronic heating system?
Answer: Lowers supply water temperature as outdoor temperature rises
Outdoor reset reduces boiler supply water temperature proportionally as outdoor temperatures warm, improving efficiency and comfort by matching heat output to actual load.
What is the purpose of a low-loss header (hydraulic separator) in a hydronic system?
Answer: To decouple primary and secondary circuits hydraulically
A low-loss header hydraulically decouples the primary boiler circuit from the secondary distribution circuits, allowing them to operate at different flow rates without interference.
When sizing a hydronic circulator pump, which two parameters are most critical?
Answer: Flow rate (GPM) and head pressure (feet of head)
Circulator pumps are selected based on the required flow rate in gallons per minute (GPM) and the total system head loss in feet of head that the pump must overcome.
In a series-loop one-pipe hydronic system, what happens to the water temperature as it progresses through successive terminal units?
Answer: Temperature gradually decreases with each successive unit
In a series loop, each terminal unit extracts heat from the same water stream, so the water temperature drops progressively from the first to the last unit in the circuit.