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

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.

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 TC 9.9 / TIA-942 5.3.5

Cables routed across perforated floor tiles obstruct cold air delivery to server inlets. Under-floor cable routing must maintain clear pathways around perforated tiles. Cable obstruction can reduce tile airflow by 50% or more.

ASHRAE TC 9.9 / TIA-942 Annex G

Propping open hot aisle containment doors defeats the purpose of airflow separation. Containment doors must remain closed and self-closing to maintain the pressure differential between hot and cold aisles.

ASHRAE TC 9.9 Thermal Guidelines

Blocking the CRAH return air path forces the unit to recirculate already-cooled air or starve for airflow, reducing capacity and creating hot spots. Return air must have an unobstructed path from the hot aisle per ASHRAE TC 9.9 best practices.