ASHRAE Handbook — HVAC Systems and Equipment, Heat Exchangers

ASHRAE Handbook — HVAC Systems and Equipment, Centrifugal Pumps

The cavitation noise (sounds like gravel passing through the pump) confirms insufficient NPSH available. Continued operation will erode the impeller vanes, damage seals, and ultimately destroy the pump. The pump must be shut down and suction piping corrected before returning to service.

ASHRAE Handbook — HVAC Systems and Equipment, Chiller Plant Piping

The condenser water return from the cooling tower is piped to the supply header instead of the return header. This reverses flow through the condenser, sending warm water from the tower back through the supply side. The chiller will see elevated condensing temperatures, causing high head pressure, reduced capacity, and potential high-pressure safety trips.

ASHRAE Handbook — HVAC Systems and Equipment, Cooling Towers

The basin heater thermostat has failed, not activating the heater in freezing conditions. Without basin heat, water in the sump and exposed piping will freeze, cracking the basin and potentially rupturing condenser water piping. Basin heaters must be verified annually before cold weather.

ASHRAE Handbook — HVAC Systems and Equipment, Primary-Secondary Pumping

The decoupler (bridge) pipe must be sized to match the largest system pipe — in this case 10". An undersized decoupler creates excessive pressure drop between primary and secondary loops, causing flow interference and unpredictable delta-T performance.

ASHRAE Handbook — HVAC Systems and Equipment, Valves

Leaking 2-way valves allow chilled water to bypass through coils that should be off, reducing system delta-T. Low delta-T syndrome forces additional chillers online prematurely and wastes energy. Valves must be replaced or repacked. ASHRAE recommends close-off pressure ratings that exceed pump shutoff head.

ASHRAE Standard 188 — Legionellosis: Risk Management for Building Water Systems

Conductivity of 4,500 µS/cm is nearly double the upper target limit, confirming excessive mineral concentration. High conductivity accelerates scale formation, promotes corrosion, and creates conditions favorable for Legionella growth. Immediate blowdown is needed to reduce conductivity to target range.