Chiller Preventive Maintenance Procedure
Chillers are the core equipment of a hotel's air-conditioning system, and their operating status directly affects the availability and energy efficiency of the entire system. According to Section 11.3 of GB 50243 "Code for Acceptance of Construction Quality of Ventilation and Air Conditioning Works" and the relevant requirements of ASHRAE Standard 180, a complete preventive maintenance system for chillers should be established, covering everything from daily inspection to annual overhaul. Daily inspection (every day): Check and record unit operating parameters, including evaporator entering/leaving water temperatures, condenser entering/leaving water temperatures, refrigerant saturation temperatures (evaporating temperature and condensing temperature), compressor current and voltage, oil pressure and oil temperature, and cooling water entering/leaving temperature difference. Observe whether unit operating sound and vibration are abnormal, and check for signs of refrigerant leakage (oil stains, bubbles). The above parameters should be recorded in the operating log and compared with baseline data to analyze trend changes. Weekly inspection: Check compressor lubricating oil level and oil quality, confirming the oil level is within ±1/4 of the center line of the sight glass; check the refrigerant sight glass indication to determine whether the refrigerant charge is appropriate (no bubbles in the sight glass is normal); check whether safety valves and pressure relief devices are intact; test whether unit loading/unloading actions are normal. Monthly inspection: Analyze unit operating data, calculate COP and EER values, and compare with design values; check water-side fouling of the evaporator and condenser, and perform backflush cleaning if necessary; check contactor contacts and wiring terminals in the electrical control cabinet for overheating and discoloration; test whether safety protection devices (high-pressure protection, low-pressure protection, antifreeze protection, oil pressure differential protection, etc.) function properly. Quarterly inspection (seasonal maintenance): Conducted before and after the cooling season. Seasonal maintenance contents: Thoroughly clean the water side of the condenser and evaporator (using chemical cleaning or mechanical brush cleaning), check the tube bundle for leakage (perform hydrostatic test if necessary); replace compressor oil (or take samples for testing and decide whether to replace based on oil test results); replace the filter drier core; perform refrigerant chemical composition analysis to detect acidity, moisture and impurity content; test compressor motor insulation resistance (not less than 2 MΩ). Annual inspection (annual overhaul): Conducted by inviting a professional maintenance company, including: compressor disassembly inspection (bearings, seals, rotor clearance, etc.); replacement of lubricating oil and oil filter; cleaning or replacement of condenser and evaporator end cover gaskets; comprehensive calibration of control system instruments and sensors; overall unit performance testing to verify key indicators such as cooling capacity and COP. Article 11.3.2 of GB 50243 stipulates that the overhaul cycle for chillers is generally 2-3 years or 15,000-20,000 operating hours. The Marriott MIDS standard requires hotels to establish chiller maintenance files recording the content, date and operators of each maintenance activity, and to retain them for at least 5 years.
Maintenance Requirements for Air Handling Units and Fresh Air Units
Air handling units (AHU) and fresh air units (PAU) are the core terminal processing equipment of a hotel's air-conditioning system, and their maintenance quality directly affects supply air quality and system energy consumption. According to Sections 7.2 and 11.4 of GB 50243 "Code for Acceptance of Construction Quality of Ventilation and Air Conditioning Works," the maintenance of air handling units and fresh air units should cover all aspects including the filtration system, heat exchange coils, fans and transmission systems, condensate drainage, and cabinet sealing. Filter maintenance: Filters are the components with the highest maintenance frequency in air handling units. G4 coarse filters are recommended to be cleaned or replaced every 1-2 months (they must be replaced immediately when the filter medium is heavily loaded with dust or the pressure differential reaches 2 times the initial resistance); F7 medium-efficiency filters should be replaced every 3-4 months; F9 sub-high-efficiency filters should be replaced every 6 months. Establish a filter pressure differential monitoring system by installing pressure differential switches or pressure differential sensors before and after the filters, and automatically alarm for replacement when the resistance reaches the set value. When replacing filters, check installation sealing to ensure there is no bypass leakage between the filter and the frame. Heat exchange coil maintenance: Check monthly whether coil fins are collapsed, corroded or blocked, and clean the coil surface at least once a year (using a dedicated cleaning agent for aluminum fins, taking care to avoid corroding the fins). Perform water-side chemical cleaning of the coils every 3 years to remove internal fouling and improve heat exchange efficiency. After 3-5 years of operation of an air handling unit, it is recommended to test the coil heat transfer coefficient; if the heat transfer coefficient drops by more than 15%, replacement is required. Fan and transmission system maintenance: Check weekly whether fan operating current and voltage are normal, check monthly fan belt tension and wear (belt deflection should be controlled within 1/64 of the center distance between pulleys), and add fan bearing grease once per quarter (the amount added should not exceed 1/3 of the bearing housing). Perform fan impeller dynamic balance testing annually (balance grade G6.3), and test motor insulation resistance. Condensate drainage system: Check monthly whether the condensate drain pan is clean and whether the drain pipe is unobstructed (to prevent algae growth and blockage); the drain pan slope should be no less than 0.5% to ensure smooth drainage. Perform high-pressure flushing of condensate drain pipes annually before the cooling season begins. Cabinet sealing and insulation: Check quarterly the sealing of the air handling unit cabinet (especially door sealing strips) to prevent energy loss caused by air leakage. Check whether cabinet insulation and pipe insulation are intact, and whether the metal casing is corroded. Article 7.2.8 of GB 50243 stipulates that when installing air handling units, the cabinet sealing should be checked, and the air leakage rate should not exceed 3%. Fresh air units also require particular attention to antifreeze protection: before winter operation, check the working status of the antifreeze switch and preheating coil, and test the antifreeze interlock function (automatically close the fresh air damper and stop the fan when the supply air temperature falls below 5°C).
Maintenance Technology for Fan Coil Units and Terminal Equipment
Fan coil units (FCUs) are the most commonly used air-conditioning terminal equipment in hotel guest rooms, with large quantities (typically 600–1,200 units per hotel) and a huge maintenance workload. According to Section 7.3 of GB 50243 "Code for Acceptance of Construction Quality of Ventilation and Air Conditioning Works," fan coil units shall undergo regular maintenance and servicing to ensure their performance meets design requirements. Preventive maintenance contents for fan coil units: (1) Filter cleaning: The return-air filters of guest room fan coil units shall be cleaned every 3 months. In operating practice, it is recommended that housekeeping staff check filter condition while cleaning rooms and clean promptly when dust accumulation is severe. Filter blockage can cause airflow to drop by 30%–50%, significantly weakening cooling performance. (2) Coil cleaning: Clean the fins of fan coil units every 6–12 months. Spray foam cleaner onto the fin surface, wait 10–15 minutes for reaction, then rinse with low-pressure clean water. Take care to protect the condensate drain pan below the coil to prevent cleaning agent from flowing into the drain pipe. After cleaning, the coil heat transfer coefficient can recover to 90%–95% of that of a new unit. (3) Condensate drainage inspection: Check monthly whether the condensate drain pan and drain pipe are blocked. Biocides and algae-control tablets should be added to the drain pan to prevent algae and microbial growth from blocking the drain pipe. The drain pipe shall be flushed at least quarterly to maintain unobstructed drainage. (4) Fan motor maintenance: Check the fan motor operating current every six months, add lubricating oil (if an oil nipple is provided), and check fan impeller balance and noise. Replace motor bearings every 2 years. (5) Thermostats and motorized valves: Check quarterly the consistency between the thermostat's displayed temperature and the actual temperature (error should be ±0.5°C), and check whether the motorized valve operates flexibly and closes tightly. It is recommended to replace motorized valve actuators every 3–5 years (preventive replacement is preferred to avoid failures affecting the guest experience). Special requirements for guest room FCU maintenance: In hotel operations, guest room FCU maintenance needs to be carried out after guests check out or while rooms are vacant. It is recommended to establish a guest room FCU maintenance schedule and arrange maintenance during periods of low room occupancy (e.g., 10:00–16:00). Maintenance personnel should carry dedicated tools and spare parts into guest rooms, and after completing maintenance, test the supply air temperature and velocity to ensure normal operation is restored. Establish an FCU maintenance information system: Each FCU should have a unique number and maintenance file, recording the date, content, replaced parts, and results of each maintenance. Use QR codes or RFID tags for equipment identification; maintenance personnel scan the code to view equipment history. The Marriott MIDS standard requires hotels to conduct a comprehensive performance inspection and maintenance of guest room FCUs at least once per year, and maintenance records shall be uploaded to the hotel asset management system.
Preparation of Preventive Maintenance Plans and Application of CMMS Systems
A systematic preventive maintenance plan and a computerized maintenance management system (CMMS) are management tools for ensuring the long-term reliable operation of hotel HVAC systems. According to the requirements of ASHRAE Standard 180 "Standard Practice for Inspection and Maintenance of Commercial Building HVAC Systems," commercial buildings should establish preventive maintenance plans for HVAC systems and record maintenance activities. The preparation of preventive maintenance plans should be based on equipment manufacturers' technical manuals and industry best practices, combined with the operational characteristics of the hotel. Four-tier structure of the maintenance plan: (1) Tier 1 - Daily inspection (daily/weekly): Completed by the duty engineer of the hotel engineering department, checking key operating parameters and equipment status, and filling in inspection record forms. Inspection contents should cover chiller operating parameters, pump operating current and vibration, cooling tower operating status, air handling unit supply air temperature and pressure, etc. (2) Tier 2 - Regular servicing (monthly/quarterly): Completed by technicians of the hotel engineering department, including filter replacement, belt tensioning, bearing lubrication, electrical inspection, etc. (3) Tier 3 - Annual maintenance (annual): Completed by the hotel engineering department or an external professional company, including heat exchanger cleaning, refrigerant recovery and charging, safety valve calibration, performance testing, etc. (4) Tier 4 - Overhaul (every 3–5 years): Completed by the equipment manufacturer or a professional maintenance company, including compressor overhaul, replacement of worn parts, control system upgrades, etc. Functional requirements of the CMMS system: (1) Asset registration: Establish an equipment ledger (including equipment number, model, installation location, maintenance history, spare parts list, etc.). (2) Work order management: Automatically generate periodic maintenance work orders (triggered by calendar time or operating hours), and assign maintenance personnel and planned completion times. (3) Mobile inspection: Maintenance personnel receive work orders, record maintenance data, and upload photos via mobile APP. (4) Spare parts management: Automatically generate spare parts procurement recommendations based on consumption data, and provide early warning of low inventory. (5) Data analysis: Generate KPI reports such as equipment failure rate, MTBF (mean time between failures), and MTTR (mean time to repair). (6) Maintenance plan optimization: Automatically adjust maintenance frequency and content based on historical data, achieving an upgrade from preventive maintenance to predictive maintenance. Investment benefits of the CMMS system: The software license and implementation cost of a small-to-medium-scale CMMS system is approximately RMB 150,000–300,000 (one-time), with an annual service fee of approximately RMB 30,000–50,000. According to industry statistics, after implementing a CMMS system, equipment downtime is reduced by 20%–40%, maintenance costs are reduced by 10%–20%, and equipment life is extended by 10%–15%. Section 10.2 of GB 50736 on operation management requirements emphasizes that maintenance and servicing records of air-conditioning systems shall be kept complete. The Marriott MIDS standard recommends that hotels use CMMS systems to manage MEP equipment maintenance.