Addressing chiller drift from design

For decades, the HVAC industry has focused heavily on replacing ageing centrifugal chillers, often assuming that age alone determines performance, efficiency and reliability. Through nearly 50 years of work across the United States, Middle East, Latin America and the Caribbean, I have found that this assumption is frequently incorrect. One of the most successful developments of my career has been the advancement and implementation of the Centrifugal Chiller Recommissioning (RCx) programme, an engineering approach designed to restore operating performance; recover lost efficiency; improve reliability and extend equipment life, regardless of the age of the chiller. This methodology has produced significant success not only throughout the Middle East but also increasingly across the United States, where facility owners are facing rising energy costs, ageing infrastructure, sustainability targets and capital budget constraints.

The problem: chiller drift from design

Very few chillers operate today as they did when originally commissioned. Over years of operation, systems experience:

• Tube fouling and condenser degradation
• Refrigerant charge imbalance
• Control drift and sensor inaccuracies
• Oil contamination
• Variable flow issues
• Improper condenser water temperatures
• Excessive lift conditions
• Inefficient loading strategies
• Partial-load instability
• Mechanical wear

A chiller may still “run”, but running is not the same as operating efficiently. In many facilities, chillers that appear reliable are consuming 15-30% more energy than design conditions while slowly losing operating margin and reliability. As a matter of fact, I have seen chillers operating at 50% inefficiency and the operations team had no idea the chiller was operating this poorly.

RCx changes the conversation

Traditional maintenance keeps equipment operational. RCx restores performance.

The objective of RCx is to return the entire machine and supporting plant to optimised operating conditions through detailed engineering analysis and corrective actions.

A complete recommissioning process evaluates:

• Compressor performance
• Heat transfer efficiency
• Evaporator and condenser approach temperatures
• Refrigerant condition and charge optimisation
• Oil quality and management
• Control sequences
• VFD operation
• Sensor calibration
• Tower performance
• Pump interaction
• Plant sequencing logic
• Seasonal operating strategies

The result is not simply maintenance; it is a return to engineered performance.

Success in the Middle East

The Middle East became one of the proving grounds for large-scale recommissioning initiatives.

Many facilities in Dubai, Abu Dhabi, Qatar, Bahrain, Oman and Saudi Arabia operate under extreme ambient temperatures and very demanding cooling loads. Chillers often run continuously under high lift conditions, making energy consumption and reliability absolutely critical.

Through RCx programmes, facilities have achieved:

• Significant reductions in energy consumption
• Improved stability during peak summer loads
• Extended operating life of existing assets
• Reduced emergency shutdown events
• Increased confidence in older machines

Some chillers previously considered candidates for replacement demonstrated years of additional reliable operation after recommissioning. The lesson was clear: Age alone does not determine replacement; performance does.

Growing success across the United States

The same principles are now delivering results throughout the United States. Many North American facilities operate centrifugal chillers that are 20, 30 and even 40+ years old. These machines are frequently well maintained mechanically but have never undergone comprehensive recommissioning.

Owners are discovering that RCx can provide:

• Immediate energy savings
• Deferred capital expenditure
• Improved sustainability metrics
• Lower operating cost per ton
• Enhanced reliability
• Better plant visibility and diagnostics

In many cases, RCx becomes the bridge between maintaining an existing asset and planning future modernisation.

RCx should become standard practice

The industry has accepted commissioning for new installations. The next evolution should be mandatory periodic recommissioning for operating chillers. Every centrifugal chiller, be it five years old or 50 years old, can benefit.

Indeed, RCx should become standard, because it addresses:

Energy efficiency: Restores lost kW/ton performance and reduces operating costs

Reliability: Identifies hidden operating deficiencies before failure occurs

Sustainability: Reduces energy use and extends asset life

Capital preservation: Allows owners to make informed replacement decisions

Operational confidence: Ensures machines perform closer to original design intent

The future of chiller optimisation

The HVAC industry is entering a period where energy, carbon reduction and reliability are no longer optional objectives, they are business requirements. RCx provides a practical and proven path forward. My experience across multiple continents has shown that a properly engineered RCx programme can transform chiller performance regardless of manufacturer, refrigerant type or equipment age. A well-maintained chiller is valuable; a recommissioned chiller becomes an optimised asset. The future of plant efficiency will not be driven only by new equipment – it will be driven by how intelligently we restore and operate the equipment already installed.

The writer is an industry-recognised expert on Large Tonnage Liquid Chillers and industrial District Cooling plants with almost 50 years industry experience. Dan is a Member of ASHRAE, RSES, IDEA, MCAA, MSCA, ACCA and The Independent Contractors Exchange Group. He may be contacted at <dmizesko@aol.com>.