CSLB C-20 HVAC ContractorHeating SystemsMedium
A hydronic heating system develops persistent air bubbles in the baseboard radiators, causing gurgling noises and reduced heat output. Which component is designed to remove entrained air from the system?
- AAir separator
- BAquastat
- CBackflow preventer
- DZone valve
Show answer & explanationAnswer & explanation
Correct answer: A. Air separator
An air separator, often installed near the boiler supply and paired with the expansion tank, collects and vents entrained air bubbles from the circulating water, preventing airlock and noise in the piping and terminal units.
Why the other options are wrong
- B. An aquastat controls boiler water temperature, unrelated to air issues.
- C. A backflow preventer stops reverse flow of water into the potable supply, not air removal.
- D. A zone valve controls flow to individual heating zones, not air removal.
Hydronic Air Separator
A device installed in a closed hydronic loop that removes entrained air bubbles from circulating water to prevent noise, corrosion, and reduced heat transfer.
- Typically installed near the boiler and expansion tank
- Uses reduced velocity or coalescing media to release air
- Air is vented via an automatic air vent at the top
Memory trick: Bubbles out, heat flows better.