This project was originally a specified design, however, it came in over budget. Summit Refrigeration Group was in the fortunate position to be one of two contractors selected to provide a design build solution for the central refrigeration system, which will cool the main 18,100sq/ft. freezer to -67°F and support areas that total approximately 5,500sq/ft with varying temps from +50°F to +15°F.
Our design team went to work with some innovative solutions, all designed with serviceability in mind considering the environment. We were successful to join the team responsible for what is said to be the largest -67°F freezer in North America. We don’t know if this is true, but it sounds pretty cool! Redundancy was on the forefront of the design, considering the temperatures needed. If the system went down, they couldn’t just move their product to a refrigerated trailer at another refrigerated ware-house since there aren’t too many -67°F facilities available. First, the design included redundancy in the coils (one in standby) as well as nitrogen sections on all of the coils in the event that the mechanical refrigeration system went down. Second, we have 100% redundancy on the compressors, pumps and designed bypass piping to allow the redirection of refrigerant if needed.
The design centered around four (4) specialty designed coil rooms that allowed for the coils to be isolated from the main area. This was accomplished by a series of low-temp damper and actuator systems (we had to heat the actuator housing) that would close and allow the coil to defrost. This also provided the ability to separate these areas to perform maintenance and service on the coils. If you’ve ever tried to service anything in -67°F temperatures, you will understand why this is so important. We worked with Colmac Coil Manufacturing to design the coils to deliver 18.5TR each, with one coil in standby at all times. The wind chill in the room, with the calculated air velocity at 30mph, is equal to -117°F.
The system was also designed around pumped ammonia (another challenge at those temps) and included stainless steel piping, a specialty steel recirculator and other vessels provided by Isotherm. When operating at -67°F, pressure drop in the piping and valve systems have a huge impact on the system operation. So we worked with Hantemp Controls on all of the ultra-low temp valve groups and used motorized ball valves. Being stainless steel, they met our design spec and the full port ball valve design provided extremely low pressure drops. On the larger isolation valves, Bray stainless butterfly valves were selected.
The compressors that were selected at 100% redundancy included two (2) Vilter booster single screw compressors designed for -76°F/-20°F, and the high stage with 100%redundancy included two (2) Vilter high stage single screw compressors designed for-20°F/+95°F. A BAC evaporative condenser, B&G water pumps, a Kelvion hot gas/glycol heat exchanger for the underfloor system, as well as Hansen Technologies and R/S (Refrigerating Specialties) valves, balanced out the rest of the design.
Controlling the humidity in the infiltrating air helps to minimize defrost and control frost build up by the entry points to the -67°F area. We worked with Climate by Design to design and select three (3) desiccant air handler systems to provide dehumidification and dry air to the entry vestibules serving the main freezer and service corridors to the coil rooms.
We turned to AAIM Controls, a Danfoss Company, to work in depth with us to come up with strategic programming, monitoring and notification systems to ensure this system would provide years of reliable operation. A separated power source system was designed to allow for the backup generator to operate part of the control system that handles the nitrogen back up cooling, as well as maintaining all the life safety systems.
Sourcing some of the specialty items integrated into our system proved to be challenging, however our Purchasing and PM team came through as usual. Try finding a strobe light to operate if the CO level rises in a -67°F environment. We actually had to add a heater to that also! A huge ‘Thank You’ to all of the Summit team members who contributed to this unique and successful project!