Project
GOING GREEN WITH COMBINED NATREF SYSTEM SOLUTION
By Ricky Savvides , HVAC and building services engineer at ACS Consulting Engineers
This project , for the largest retailer in South Africa , comprised several HVAC and refrigeration aspects as the planned new benchmark for future sites , ticking the boxes of efficiency and low environmental impacts .
ACS Consulting Engineers ( ACS ) were appointed by
Massmart to design the HVAC , refrigeration , and plumbing and drainage aspects for their new store in Parsonsvlei , Gqeberha . This would be the eleventh new Makro store designed by ACS , this one however with a major twist .
Designs for the project began in 2019 and construction commenced in early 2020 - although due to the COVID -19 pandemic it was subsequently delayed . The project thus reached completion in April of 2021 .
PROJECT SPECIFICATIONS AND FACILITY REQUIREMENTS The client brief was to provide an energy efficient system for the facility ’ s HVAC and refrigeration requirements that is sustainable , that uses low ozone depleting potential ( ODP ) and global warming potential ( GWP ) refrigerants , that provided a combined system that would offer economy of scale including thermal storage , and which would produce hot water from free heat captured from the system . is provided from the same system , and that the refrigeration requirements are met .
Two racks were installed - each with two packs incorporating medium , low and HVAC Bitzer compressors ( each for 50 % capacity ), electrical distribution boards and controls . Each rack comprises four HVAC compressors , four MT compressors , three LT compressors and three intermediate compressors .
LT compressors discharge into MT compressors and the lead compressors incorporate VSDs .
Refrigeration capacity was approx . 400kwR for MT and LT applications per pack . HVAC capacity was approx . 470kWR in day mode and 370kw in ice mode per pack . All compressors discharge
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THE HVAC & R SYSTEM SOLUTION AND RATIONALE The twist of this particular facility was the first occurrence in the eleven sites handled by ACS in the requirement for a design to combine the HVAC and refrigeration systems onto a set of common CO 2 chillers / packs using two-stage transcritical booster packs with parallel compression operating above and below the critical point of 31 ° C and above the triple point of 38 ° C , and , at high compressor discharge pressures between 7 500-10 000 Kpa as the heart of the two systems . The site further incorporated the now standard Massmart request for thermal storage for the HVAC portion , the low ( LT ) and medium temperature ( MT ) cold rooms , freezers , and cabinets on the refrigeration installation , and to provide hot water for domestic use and winter space heating .
At time of completion , ACS believes this was the first combined project of its kind in South Africa , especially because of its capacity and the fact that ice thermal storage was used for HVAC , domestic hot water , that winter heating
RACA Journal I January 2023
All image credits © ACS Consulting Engineers
A walk-around freezer in assembly . www . refrigerationandaircon . co . za