A hydronic heating system is being installed in a commercial building. To ensure proper heat delivery and prevent air-related issues, the air separator should be installed at which location in the system?
- AOn the discharge side of the circulator pump.
- BOn the supply line, just after the boiler.
- COn the return line, just before the boiler.
- DOn the suction side of the circulator pump.
Show answer & explanationAnswer & explanation
Correct answer: B. On the supply line, just after the boiler.
An air separator is most effective when installed on the supply side of the boiler, immediately after the boiler and before the circulator pump (if the pump is on the supply side, which is often preferred for 'pumping away'). At this point, the water is at its highest temperature and lowest pressure (relatively), causing dissolved air to come out of solution as bubbles, which the separator can then efficiently remove.
Why the other options are wrong
- A. If the circulator is on the return, placing the air separator after it on the discharge (supply) side is effective, but generally, the ideal spot is immediately after the boiler.
- C. On the return line, water is cooler, and air is more likely to remain dissolved or be entrained. The highest temperature, lowest pressure point is ideal.
- D. While some air might be removed here, the water is cooler and under higher pressure, making air separation less effective.
Air Separator Placement
The optimal location for an air separator in a hydronic system is where the water is hottest and under the lowest pressure, typically on the boiler supply, to maximize the removal of dissolved and entrained air.
- Prevents noise, corrosion, and inefficient heat transfer.
- Highest temperature, lowest pressure point is ideal.
- Often paired with the expansion tank connection.
Memory trick: Boiler's hot, air bubbles float, separator's there, to keep them out of the boat.