What does a closed chilled water system require?

What does a closed chilled water system require?

• A. Open reservoir
• B. Pressure-rated expansion tank
• C. Bypass valve
• D. Unpressurized tank

Answer: (B)

In a closed chilled water loop, the liquid is confined and cannot escape to the atmosphere, so it must be able to expand without causing dangerous pressure buildup. The way this is accomplished is with an expansion device that is designed to withstand the system’s operating pressure. A pressure-rated expansion tank provides a flexible volume (often with a bladder or diaphragm) that compresses as water expands when heated, keeping the loop pressure within design limits and preventing stress on the piping, pumps, and equipment. An open reservoir would defeat the purpose of a closed system by creating an atmospheric vent and allowing continual water level and pressure changes, along with air ingress. An unpressurized tank wouldn’t offer a stable cushion to absorb thermal expansion. A bypass valve serves flow balancing or maintenance needs, not the expansion compensation essential to a closed loop.

In a closed chilled water loop, the liquid is confined and cannot escape to the atmosphere, so it must be able to expand without causing dangerous pressure buildup. The way this is accomplished is with an expansion device that is designed to withstand the system’s operating pressure. A pressure-rated expansion tank provides a flexible volume (often with a bladder or diaphragm) that compresses as water expands when heated, keeping the loop pressure within design limits and preventing stress on the piping, pumps, and equipment.

An open reservoir would defeat the purpose of a closed system by creating an atmospheric vent and allowing continual water level and pressure changes, along with air ingress. An unpressurized tank wouldn’t offer a stable cushion to absorb thermal expansion. A bypass valve serves flow balancing or maintenance needs, not the expansion compensation essential to a closed loop.