ASHRAE Handbook — HVAC Systems / ASME B31.9

ASHRAE Handbook — HVAC Applications

Rooftop units must have vibration isolation to prevent noise and vibration transmission to the building structure. Required by ASHRAE and most building codes.

ASHRAE Handbook — HVAC Applications, Water Treatment

Visible scale on condenser tubes indicates water treatment failure. Scale acts as insulation on heat transfer surfaces — 1/16" of scale increases energy consumption by approximately 11%. The condenser must be chemically or mechanically cleaned, and the water treatment program must be corrected to prevent recurrence.

ASHRAE Handbook — HVAC Systems

Hot water reheat coils must have isolation valves for maintenance and balancing. Without them, the entire zone piping loop must be drained for any coil work.

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.