ASHRAE Handbook — HVAC Systems and Equipment, Chiller Plant Piping
What it means on the job
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.
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Related ASHRAE sections
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 / ASME B31.9
Valve stems and packing glands must not be insulated over. Covering valve operators prevents maintenance access and traps moisture that accelerates stem corrosion and packing failure.
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, 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, Heat Exchangers
Heavy scale buildup on heat exchanger plates indicates failed water treatment. Fouling reduces heat transfer efficiency and increases pressure drop across the exchanger. Scale deposits as thin as 1/32" can reduce heat transfer by 25%. The plates must be cleaned with an approved chemical descaler and water treatment program corrected.
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.
CraftIQ explanations are original educational commentary written in trade language and verified against the cited standards. Always confirm requirements against the code edition adopted by your jurisdiction — this is training material, not a substitute for the code book or your AHJ.