Case Study
Main AHU Chiller Replacement at York Hospital
Overview
Client: York Hospital
Industry: Healthcare
Project Overview: Newsome replaced two ageing air-cooled chillers serving the main AHU chilled water system at a hospital in York. The project included a rooftop crane lift, new stainless steel pipework, electrical works, insulation and commissioning, resulting in a more efficient and resilient cooling system.
Newsome was appointed to replace two ageing air-cooled chillers serving the main air handling unit cooling circuit at a hospital in York.
The project followed a detailed site evaluation focused on improving the overall energy efficiency, resilience and long-term performance of the existing chilled water system. The original installation used two York YAES 0415 air-cooled chillers. Following technical assessment, Newsome recommended replacing the existing units with new high-efficiency air-cooled chillers using low-GWP R454B refrigerant.
The completed project included removal of the old chillers from the roof, installation of two new units, new stainless steel pipework, electrical modifications, insulation, commissioning and final water quality checks.
The Challenge
The existing chillers were ageing and significantly less efficient than current-generation equipment. The system served the main AHU cooling circuit and had been designed around a duty of approximately 379.5kW, with chilled water supplied at 7°C and returned at 12°C.
During the original assessment, one of the existing chillers had already failed while the second remained operational. This made resilience a major concern and meant the replacement programme had to be carefully phased to maintain cooling availability throughout the works. The project also presented a significant logistical challenge because both existing chillers were located on the roof.
Their removal and replacement therefore required a carefully planned contract lift from the main car park, with the crane operation scheduled at the weekend to minimise disruption to hospital services.
Evaluating Energy Performance
Before the replacement was specified, Newsome carried out an energy and running cost analysis comparing the existing York chillers with new high-efficiency alternatives. The assessment considered expected operating conditions, cooling capacity and seasonal weather data based on the Leeds area.
The analysis indicated that replacing the existing chillers could reduce annual power consumption across the cooling system by approximately 28%, with the detailed single-unit comparison indicating an estimated efficiency improvement of around 33% under the assessed operating profile. This provided a strong technical case for replacement rather than continuing to invest in an ageing plant.
Newsome also evaluated the potential benefits of fitting adiabatic spray systems to both existing and replacement equipment. This allowed the client to understand the relative efficiency gains available from improving existing plant compared with investing in new equipment.
Selecting the Replacement Chillers
Newsome selected two CGAF 105 HE LN air-cooled chillers for the project.
Each chiller was capable of providing approximately 395kW of nominal cooling, comfortably meeting the required design duty while providing improved operating efficiency. The units incorporated scroll compressors and two independent refrigeration circuits, helping improve resilience if a refrigeration circuit required maintenance or experienced a fault. The chillers were also designed for external installation and offered a wide operating range, making them suitable for year-round operation at the hospital.
Moving to Low-GWP Refrigerant
An important part of the specification was the choice of refrigerant.
The new chillers used R454B, a lower-GWP alternative to older refrigerants such as R410A. R454B has a substantially lower Global Warming Potential than R410A, helping reduce the environmental impact associated with the refrigeration system while providing comparable heat transfer performance. Selecting a lower-GWP refrigerant also gave the hospital a more future-focused system as environmental legislation continues to drive the phase-down of higher-GWP refrigerants.
Careful Planning Around Live Hospital Operations
Replacing a major rooftop plant at an operational hospital required detailed sequencing.
Before work started, a Newsome Contracts Manager completed a project review meeting and agreed to the programme of works with the site team. Risk assessments and method statements were also produced for the complete installation. The failed chiller was disconnected first during a standard working day.
The main crane operation then took place at the weekend. The remaining operational chiller was isolated and disconnected before both existing units were lifted from the roof and the replacement chillers positioned. This staged approach reduced disruption and allowed the first new chiller to be connected and commissioned before work progressed onto the second unit.
Complex Contract Lift
The rooftop location meant removal and positioning of the equipment required a full contract lift. The crane was positioned within the hospital car park and the operation was scheduled outside normal weekday activity to reduce the effect on staff, visitors and hospital services. Local restrictions on mobile crane weights also had to be considered. The selected crane was transported without its ballast, with ballast delivered separately under the appropriate movement arrangements.
Once positioned, the crane removed both existing chillers and lifted the new units onto the roof in a single planned visit.
New Stainless Steel Chilled Water Pipework
Following positioning of the new equipment, Newsome’s pipework engineers installed new DN100 stainless steel pipework between the existing valve arrangements and the replacement chillers. The pipework was sized around the required chilled water flow and incorporated the necessary valves and fittings for isolation, filtration and flow control. All new pipework was appropriately supported using fabricated brackets, pipe clips and threaded rod in accordance with relevant installation standards. Once complete, the chilled water system was filled, vented and pressure tested before final commissioning.
Electrical Installation
Newsome’s electrical engineers isolated and removed the existing supply and control connections from the old chillers. The electrical installation was then adapted for the replacement equipment, including installation of IP-rated junction boxes where required and extension of existing control cabling. All cables were glanded, terminated, tested and energised before the chillers were commissioned. A NICEIC electrical certificate was provided following completion of the electrical works.
Water Quality and System Protection
Water quality is particularly important when new chillers are connected to an existing chilled water circuit. Before installation, Newsome collected a sample of the circulating fluid and arranged independent laboratory analysis. This provided an indication of the condition of the system fluid before the new equipment was connected and allowed any required corrective actions to be identified.
Following completion of the installation, a further sample was taken to confirm that the circulating fluid met the chiller manufacturer’s water quality recommendations. This approach helped protect the new heat exchangers and other components against corrosion, scale, sludge and microbiological fouling.
Thermal Insulation and Weather Protection
All new chilled water pipework was insulated using 30mm thermal insulation, with joints fully sealed. Valves, strainers and flanges requiring future access were provided with removable pre-insulated covers to simplify maintenance. External insulation was weatherproofed using PIB sheeting, helping protect the system from rain and external environmental conditions. Existing insulation around the modified sections was also repaired where required to leave the completed installation properly protected.
Commissioning the New System
Once the first chiller had been mechanically and electrically connected, Newsome filled the circuit and brought the unit into operation. A Newsome Service Engineer then completed full commissioning against the available heat load and produced commissioning records. The second chiller was connected and commissioned following the same process. This phased approach allowed the installation to return to full operational capacity progressively while reducing the risk associated with taking the complete cooling system offline at the same time.
Improved Efficiency and Resilience
The completed project replaced two ageing York chillers with modern, high-efficiency equipment using lower-GWP refrigerant. The new installation provided the cooling capacity required for the hospital’s main AHU system while significantly reducing the estimated annual energy demand compared with the previous plant. The two independent refrigeration circuits within each chiller also improved system resilience, while the new pipework, controls and electrical infrastructure provided a stronger foundation for future operation and maintenance.
The Outcome
Newsome successfully completed the full replacement of the hospital’s main AHU chillers, including removal and ethical disposal of the old equipment, a complex rooftop crane lift, new stainless steel pipework, electrical works, insulation, water quality checks and commissioning. The result was a more efficient, lower-GWP and more resilient chilled water system designed to support the hospital’s air handling requirements for years to come. The project demonstrates Newsome’s ability to manage complex chiller replacement programmes in live, operational environments where careful planning, engineering expertise and continuity of service are essential.