Nanjing Central Air Conditioning Cleaning & Maintenance Service

1. Overview of Central AC Maintenance Demand in Nanjing

As a megacity in the Yangtze River Delta, Nanjing experiences distinctively hot and humid summers, with an air conditioning cooling season lasting up to 5 months (late May through early October) and extreme temperatures reaching above 40℃. The urban core, Jiangbei New District, and Jiangning Development Zone concentrate a large number of commercial complexes, office buildings, star-rated hotels, and high-tech manufacturing enterprises — all of which widely depend on large-scale central air conditioning systems to maintain indoor environments.

According to Nanjing Municipal Bureau of Statistics data, the tertiary sector accounted for over 65% of GDP in 2025, with AC coverage approaching 100% in commercial, financial, and technology service buildings. On the industrial side, electronics manufacturing, biomedical, and automotive parts enterprises in Jiangning and Pukou Districts extensively use chillers and constant temperature/humidity AC systems. The main challenges currently facing central AC system operation and maintenance in the Nanjing area include: scaling and biofouling deposition from long-term cooling water system operation, gradual annual decline in refrigerant system efficiency, and air quality hazards such as mold growth in ventilation ducts.

As large integrated electromechanical systems, central AC systems left uncleaned for extended periods not only increase energy consumption by 15%~30% but also cause reduced cooling capacity, shortened equipment lifespan, and even public health risks from pathogen proliferation such as Legionella. Therefore, the national "Hygienic Specification for Central Air Conditioning Ventilation Systems in Public Places" explicitly requires regular central AC system cleaning — generally 1~2 times per year for commercial buildings and quarterly maintenance for industrial cleanrooms.

2. Analysis of Common Central AC Problems in Nanjing

2.1 Cooling Water Quality and Scaling Characteristics

Surface water in the Nanjing area is primarily sourced from the Yangtze River, with medium-to-hard water quality: total hardness approximately 120~180 mg/L (as CaCO₃) and Cl⁻ content approximately 20~40 mg/L. Under open-loop circulation conditions, the central AC cooling water system continuously evaporates and concentrates, with Ca²⁺ and Mg²⁺ concentrations in the circulating water gradually rising. Upon contact with atmospheric CO₂, CaCO₃ scale layers form and adhere to the inner walls of condenser copper tubes. Each 0.6mm increase in scale thickness reduces heat exchange efficiency by approximately 20% and increases compressor energy consumption by approximately 10%.

Simultaneously, in Nanjing's hot and humid summer environment, algae and biofouling readily proliferate on cooling tower fill surfaces. These organic materials intertwine with inorganic scale to form composite fouling, making chemical cleaning significantly more difficult than for purely inorganic scale.

2.2 System Types and Common Faults

The distribution of central AC system types in Nanjing is as follows: commercial buildings predominantly use Freon chiller + cooling tower configurations, with some earlier projects employing lithium bromide absorption units; industrial plants mostly use large screw-type or centrifugal chillers; high-end office buildings and hotels often feature independent ductwork systems and terminal fan coil units. Common issues by system:

3. Central AC Cleaning Technical Solutions

3.1 Condenser Chemical Cleaning Process

For the typical CaCO₃ + biofouling composite scale in the Nanjing area, a three-step process of "biocide stripping → acid descaling → neutralization passivation" is employed:

Step 1: Biocide Stripping. Add non-oxidizing biocide (e.g., isothiazolinone) and slime stripping agent to the cooling water system, circulate for 4~6 hours to disperse and detach biofilm from metal surfaces. This step is crucial for the algae problems prevalent in Nanjing summers — if skipped and acid cleaning is performed directly, the acid solution cannot effectively contact the underlying inorganic scale.

Step 2: Acid Descaling. Use 5%~10% Sulfamic Acid as the primary agent, supplemented with corrosion inhibitor BTA (Benzotriazole) and Lan-826, pH controlled at 2~3, ambient temperature circulation cleaning for 4~8 hours. Sulfamic Acid has strong CaCO₃ dissolution capability with extremely low corrosion rates on copper tubes (≤0.5 g/m²·h), making it the preferred acid for copper tube condenser cleaning. For stainless steel plate heat exchangers, switch to Citric Acid 3%~5% formulation to avoid Cl⁻-induced stress corrosion cracking.

Step 3: Neutralization and Passivation. After acid cleaning, drain the acid solution, flush with clean water to pH≈6, add Na₂CO₃ (Sodium Carbonate) for neutralization, then apply NaNO₂ (Sodium Nitrite) 0.5%~1% or Sodium Molybdate passivation treatment to form a protective film on copper tube surfaces.

3.2 Lithium Bromide Unit Cleaning and Maintenance

The cleaning focus for lithium bromide absorption units is chemical descaling of generator copper tubes and solution regeneration. Using a Sulfamic Acid 8% + BTA 0.3% formulation, check vacuum recovery after circulation cleaning. Simultaneously check solution concentration and pH, performing solution filtration for impurity removal or replacement/regeneration as needed. For some 20+ year-old legacy units in Nanjing, special attention must be paid to copper tube ammonia corrosion issues — copper tubes in contact with ammonia during operation form cuprammonium complex ions, and the risk of tube wall thinning cannot be ignored.

3.3 Cooling Tower and Ductwork Cleaning

Cooling towers are cleaned using high-pressure water jetting at 15~25 MPa, combined with biocide/algaecide immersion treatment. Ductwork systems are cleaned using mechanical brushing + negative pressure vacuuming, with dust accumulation and microbiological indicator testing conducted after cleaning in accordance with the "Hygienic Specification for Central Air Conditioning Ventilation Systems in Public Places."

4. Service Coverage and Response Mechanism

Danyang Blue Star Cleaning serves all 11 municipal districts of Nanjing:

Response time: Urban core districts: on-site inspection within 4 hours; new urban districts: within 8 hours. 24-hour standby for emergency repairs. Danyang is approximately 90 km from downtown Nanjing, with a 1~1.5 hour drive, enabling same-day round-trip operations.

Service process: Free on-site inspection → scale sample analysis → customized cleaning solution → service contract signing → site mobilization → quality acceptance → maintenance recommendations → regular follow-up visits.

5. Local Cleaning Case Studies

Case 1: Lithium Bromide Unit Cleaning at a Nanjing Commercial Complex

This complex is located in the Hexi CBD of Jianye District, using two 2 million kcal lithium bromide absorption units. After 11 years of operation, cooling capacity had dropped by approximately 35%. On-site testing revealed: CaCO₃ scale thickness on generator copper tube inner walls approximately 1.2mm, solution concentration deviated 15% from normal values. The Sulfamic Acid 8% + BTA formulation was used for circulation cleaning for 6 hours, achieving >95% copper tube descaling rate; simultaneous solution filtration and regeneration treatment was performed. After cleaning, unit cooling capacity was restored to 92% of rated value, with annual natural gas savings of approximately 80,000 m³.

Case 2: Online Condenser Cleaning for a Nanjing Pharmaceutical Enterprise Chiller

This pharmaceutical plant is located in Jiangning High-Tech Zone, with 4 screw-type chillers used for cleanroom temperature and humidity control. Since production could not be interrupted, an online chemical cleaning protocol was adopted: a cleaning pump station was connected in parallel to the cooling water pipeline, injecting Sulfamic Acid 5% + corrosion inhibitor, with circulation flow rate controlled at 0.5~1.0 m/s, cleaning duration 8 hours. After cleaning, the condenser approach temperature (difference between condensing temperature and cooling water outlet temperature) decreased from 6.8℃ before cleaning to 2.1℃, with unit COP improving by approximately 18%.

6. Why Choose Danyang Blue Star Cleaning?

• China Industrial Cleaning Association member, 20 years of professional experience, serving the Nanjing market for over 15 years, having provided central AC cleaning services to over 50 enterprises and institutions in the Nanjing area
• Dual technology full coverage: Chemical cleaning + high-pressure water jet cleaning, customized optimal solutions for different scale types and equipment materials
• Safety and environmental compliance: Cleaning agent formulations use biodegradable environmentally friendly acids, waste liquid is neutralized and discharged in compliance with standards; operators are certified and equipped with full PPE protective gear
• Complete central AC system cleaning capability: Covering chillers, lithium bromide units, cooling towers, ductwork systems, and terminal coils, providing one-stop cleaning and maintenance services
• Rapid response: Danyang to Nanjing in 1 hour direct access, 4-hour emergency response in urban core districts, without disrupting commercial operations or production schedules