1. Common HVAC System Issues
Common HVAC construction issues: Excessive air duct leakage — Causes: poorly sealed seams, unsealed flange gaskets, unsealed reinforcement holes. Solution: Strengthen self-inspection during fabrication; after installation, perform light-leak testing for low-pressure ducts or leakage rate testing for medium/high-pressure ducts. Air-conditioning water pipe hydraulic imbalance — large terminal temperature differential, near-end cold and far-end hot — Causes: no balancing valves installed or balancing valves not commissioned. Solution: Install static/dynamic balancing valves and perform hydraulic balancing commissioning so that flow deviation of each branch is ≤15%. Condensate pipe blockage causing water leakage — Causes: insufficient slope, no vent provided in trap, pipe with no slope.
2. Common Plumbing and Drainage System Issues
Common plumbing and drainage system issues: Poor drainage and backflow at sanitary fixtures — Causes: drainage pipe slope less than 0.5%, pipe blockage, poor venting system. Solution: Ensure drainage pipe slope ≥0.5% (except vertical stacks); use oblique wyes for horizontal pipe connections; provide cleanouts on each floor at 1 m above floor; vent stack extending through roof shall be no less than 1/2 the diameter of the drainage stack. Low terminal temperature in hot water system — Causes: circulation pipeline does not form a loop, return pipe design unreasonable, circulation pump undersized. Solution: Adopt reverse-return hot water circulation system; return pipe diameter no less than 1/2 the supply pipe diameter; circulation pump head calculated based on the most unfavorable loop.
3. Common Electrical System Issues
Common electrical system issues: Frequent tripping of residual current devices — Causes: poor line insulation with insulation resistance less than 0.5 MΩ, equipment leakage, MCCB undersized so normal leakage current plus equipment starting current causes tripping. Solution: Troubleshoot line insulation using a megohmmeter to test circuit by circuit; check suspect equipment such as electric water heaters and kitchen appliances. Cable overheating — Causes: insufficient ampacity, undersized design or actual load exceeding rating, poor heat dissipation, high joint resistance. Solution: Calculate actual load current, check joint quality with infrared thermal imaging, add heat dissipation measures or replace with larger cross-section cable. Excessive neutral-to-ground voltage greater than 2V — Causes: three-phase imbalance, undersized neutral conductor, poor grounding.
4. Construction Commissioning and Cross-Operation Issues
Common construction commissioning issues: Chaotic commissioning sequence — failing to follow the principle of single equipment first then system, no-load first then loaded — making problem localization difficult. Solution: Develop a detailed commissioning plan specifying commissioning steps and acceptance criteria. Uncalibrated commissioning instruments — e.g., large deviations in flow meters and thermometers — leading to inaccurate commissioning data. Solution: Send all instruments for inspection and calibration before commissioning, valid for 1 year; perform on-site comparison among multiple meters. Excessive noise and vibration — equipment foundations without vibration isolation or with failed vibration isolation. Solution: Check vibration isolator quality before equipment installation; measure vibration after installation of important equipment, ≤4 mm/s.