HVAC Maintenance: Tiered Maintenance for Screw Chillers and Modular Air-Cooled Chillers

For chillers, all of the HVAC Maintenance tasks are to be performed in strict compliance with the currently applicable industry standards for new Screw Chillers Maintenance and for Air-Cooled Chillers Maintenance. For these tasks the primary references are GB/T 18430.1-2024 “Steam compression cycle Air Cooled Chiller for industrial/commercial use” and T/GXAR 005-2024 “Operation and maintenance regulations for refrigeration mACHine rooms” and GB 9237 “Safety regulations for refrigeration systems”. These standards list out the scheduled inspection frequency and corresponding acceptance criteria, which together form the basis of the work to be done in performing the scheduled maintenance on chillers in order to safely maintain their reliable operation.

Chillers, like people, require regular maintenance to operate at peak efficiency. (Image: Deiiang™)

Our team at Deiiang™ has implemented a structured tiered approach to discover potential failures at the Daily, Monthly, Quarterly, Semi-annual and Annual levels. The approach is implemented as checklists to screw chillers and modular air-cooled heat pumps that can be immediately put to use by the facility managers, under the technical leadership of Jason.peng, product designer of Deiiang™.

Daily Routine Inspection

The daily checks of HVAC Maintenance are very important and usually recorded by the operators for both screw and air-cooled chillers on a shift basis. Below you will find a summary of the most important inspection points for the daily checks and as you can see, the Screw Chillers Maintenance requires more attention for the oil-level and the sound of the compressor than the Air-Cooled Chillers Maintenance requires attention for the air inlet / outlet temperature-differentials and the fin condition.

Unit-Specific Daily Inspections

While a universal checklist for all types of compressors and chillers is provided, specialized maintenance procedures are described for the different types of compressors. In particular, for centrifugal chillers it is important to monitor the compressor speed to avoid surge. Also, for screw chillers, it is crucial to check whether the rotors are running smoothly and to look for oil circuit pressure relief or seal leakage. Magnetic bearing units require particular attention to the bearing levitation and to the temperature of the Variable Frequency Drive (VFD) module. Air-Cooled Chillers require special maintenance of the outdoor fans as well as of the air flow passages through the fan coil units to ensure that there is no dust blockage between the fin folds.

Fig. 2: Daily logging of evaporator and condenser pressures is fundamental to chiller longevity.

Monthly Maintenance

In addition to the routine checks on a daily basis, Monthly HVAC Maintenance allows for trend analysis and protective device verification by compiling the monthly data and comparing it against the same data from the previous year as well as the rated parameters for the piece of equipment. Typically this type of analysis would highlight any deterioration of the Screw Chillers Maintenance or Air-Cooled Chillers Maintenance prior to it becoming a critical issue. This approach is at the core of the Deiiang™ service offering promoted by Jason.peng.

Unit-Specific Monthly Tasks

The following are the monthly maintenance activities required for Screw Chillers and Centrifugal Chillers. The Magnetic bearing units require testing of the VFD for the Magnetic bearing and the Power supply modules for the bearing. The Air-Cooled Chillers require cleaning of debris from the fins of the tubes and a stand by check of the defrost system.

Quarterly Maintenance

Quarterly HVAC Maintenance focuses on the fundamental aspects of the air conditioning equipment’s structure and dynamic parts. For example, the water flow switch needs to be checked for sensitivity and interlocks to ensure that the chiller safely trips in case of no flow. This is a critical safety function and is addressed in the Screw Chillers Maintenance or Air-Cooled Chillers Maintenance program. In addition to the water flow switch, the foundations for all of the equipment, the vibration isolators and the various parts of the drivetrain (motors, fans, compressors, etc.) should be inspected for any signs of wear or settling.

Unit-Specific Quarterly Checks

During the quarterly Screw Chillers Maintenance check it’s a good idea to pay attention to the compressor shaft seal lubrication/cooling system for possible leakage. For the magnetic bearing chillers, measure the bearing clearance and check the variable frequency drive for proper heat dissipation. Air-Cooled Chillers Maintenance checks should include inspection of fin deformation and ensure proper cooling of the fan motor.

Quarterly inspection of heat exchanger approach temperatures reveals fouling trends.

Semi-Annual Maintenance

Within Semi-annual HVAC Maintenance we are now entering into the deeper cleaning of the HVAC components as well as electrical insulation testing. Dirt is removed from the accumulated deposits in the sumps of the cooling towers as well as from the water distribution pans of these towers, which strongly influences the heat transfer. The electrical insulation is checked by measuring the insulation resistance. This has to be within the limits given in GB/T 18430.1-2024. Vibration and noise of the whole system are measured and by comparing with the measurement data from the factory the Bearing can be checked for wear. This is also the target of the Screw Chillers Maintenance as well as of the Air-Cooled Chillers Maintenance.

Unit-Specific Semi-Annual Tasks

For screw and centrifugal chillers, clean the oil circuit filters. For Magnetic bearing chillers, recheck the variable frequency parameters and clean the control cabinet of any dust. For Air-Cooled Chillers, test defrost system and four-way reversing valve for proper operation as part of heat pump maintenance.

Annual Maintenance

The Annual HVAC Maintenance is the most in-depth service offered at Deiiang™ by Jason.peng. This pre-cooling season startup (April–May) and in-season sustained operation (May–September) maintenance program for Screw Chillers Maintenance and Air-Cooled Chillers Maintenance is designed to return your HVAC systems to near-factory form by having a complete lubrication system over-hauled, the heat exchanger’s cleaned deep and the safety valve(s) calibrated. Jason.peng recommends this service to be completed by an authorized service provider.

Pre-Cooling Season Startup (April–May)

Cooling Season Operation Period (May–September)

For the cooling season, continue performing the daily, monthly, and quarterly work for the HVAC Maintenance as appropriate. Review and document the operating data on a weekly basis and fix any faults as they occur. Minor issues can become major problems during periods of high load for both the Screw Chillers Maintenance and the Air-Cooled Chillers Maintenance. The Deiiang™ approach is to perform a dedicated weekly review of trend logs to detect any efficiency drift.

Annual deep cleaning and oil replacement restore chiller efficiency and reliability.

Maintenance Cycle and Standard Basis Summary

Below is a table showing all of the complete scheduled maintenance for all types of Chillers and compare to other HVAC equipment. Use this table to plan maintenance for the Screw Chillers and the Air-Cooled Chillers as well as other equipment at the facility on a yearly basis according to the respective published standards.

References

• GB/T 18430.1-2024 — Steam compression cycle Part 1: Industrial or commercial and similar. View Standard

• T/GXAR 005-2024 — Refrigeration Room Operation and Maintenance Procedures. View Standard

• GB 9237 — Refrigeration System Safety Specifications. View Standard

• iso 5149-1:2014 — Refrigerating systems and heat pumps — Safety and environmental requirements. View Standard

• Deiiang™ HVAC Maintenance Documentation. Visit Deiiang™

© Deiiang™ · Product Designer: Jason.peng · All rights reserved.