Project Case Study: Ice Rink Chiller Replacement – The Fessenden School

Lesson: Assessing the building as a holistic integrated system can reveal benefits that are not obvious when looking at individual components.

Background: The chiller equipment had reached the end of its useful life. RPM was asked to review project quotes from two different mechanical contractors and provide guidance on suggested equipment replacement.

Strategy: After reviewing the quotes, RPM observed operations and data logged critical systems. We then developed a holistic solution that took rink operations and the building envelop into consideration.

Outcome: By taking this approach, we significantly improved efficiency, downsized equipment, reused some ancillary equipment, reduced on-going maintenance costs, and qualified for additional utility incentives. The integrated solution is expected to save approximately 225,000 kWh and nearly $34,000 annually (calculated at $0.15/kWh). Maintenance, peak demand and some thermal savings are added benefits. In addition, the project received approximately $60,000 in utility incentives.

RPM's Role:

  • Converted the Zamboni from gas to propane because it burns more cleanly. This allowed us to reduce ventilation flows, and the load on the new chiller, while maintaining superior indoor air quality for minimal cost.
  • Refurbished and added new controls to a legacy air handler and chilled water coil unit further reducing the design load on the new chiller at minimal cost.
  • Taken together, the above measures enabled us to downsize the new chiller and pump equipment. This reduced first cost, operational costs and increased incentive dollars. These measures also eliminated fogging inside the arena during summer months and improved the quality of the ice surface.
  • Rather than a like-for-like replacement, RPM evaluated multiple compressor designs resulting in a switch from a reciprocating to screw compressor model. The screw compressor is a better fit for this application and will result in lower first cost plus reduced maintenance and on-going operating costs.
  • Adding efficiency measures to the chiller system design yielded additional energy savings and higher incentive dollars. These included chiller controls, time scheduling, VFD motor control, activity-based infrared ice temperature reset, hot water wash down controls, and remote system access. RPM also recommended construction details, such as housekeeping pads, to facilitate on-going maintenance of the mechanical room.
  • During initial explorations, we found incompatibilities between the proposed chiller system and the existing electrical service that would have caused equipment interruptions down the road. Our holistic approach included design and installation of new electrical service to avoid such problems.
  • We determined that some ancillary equipment, like the water tower, could be repaired and reused at significant cost savings to the School. The low-e ceiling and lighting fixtures were also adequate and not cost-effective to replace.
  • Operator training was included as an integral part of the chiller contract.
  • We also optimized and administered utility incentive process.

Next Steps: Additional opportunities related to the overall ice rink structure are being explored including an ice melt pit, building shell insulation, fuel conversion, entryway changes and parking lot upgrades.

In addition, RPM is working with School management to improve efficiency and increase the focus on sustainability elsewhere on campus. To date, we have completed lighting retrofits, steam-trap repairs, a review of third-party suppliers, and a boiler replacement. Prioritization of other campus-wide as well as building specific opportunities is underway.