Projects
1
Each rack has six Frascold semi-hermetic compressors, two on
the medium temperature circuit (-5 o C suction), two on parallel
compression/MT and two much smaller compressors on the
low temperature. The installed refrigeration power on each
rack totals 98kWr on MT/Parallel and 15kWr on LT.
Built and tested at the Mainstream Refrigeration factory in
Ottery, the overall dimensions of racks fit through a standard
height doorway.
REDUCTION IN ENERGY USAGE
2
3
CO 2 as a refrigerant with zero ODP and a GWP of 1, has
reduced the environmental carbon footprint of Woolworths’s
refrigeration plants and with other interventions, has reduced
energy usage.
Variable speed drives on each rack compressor to balance
the temperature set point closely with the refrigeration
demand of all the cabinets and cold freezer rooms is one of
many design features to reduce energy usage to a minimum.
Floating suction temperatures to match demand, electronic
expansion valves, parallel compression, EC variable speed
fans (4 x 800mm diameter) on each of the two roof mounted
gas coolers, air defrost on the MT cabinets, alarms to warn
when cold room doors are left open, all contribute towards
lower energy usage. For food safety and quality control, the
temperature of product in the different cabinets are closely
monitored by probes in artificial ‘hams’ which have the same
thermodynamic properties as the actual product in the
cabinets, for example chicken, cheese, milk.
1.
2.
3.
4.
4
5.
In the event of a severe CO 2 leak in the plant room a fan
automatically exhausts the CO 2 from ground level via
a duct. A CO 2 sensor is mounted close to the inlet to the
exhaust duct.
Backup cold stores are fitted with Thermo Coil CO 2
evaporator blowers.
The store has two backup low temperature stores.
Cold room doors are fitted with a ‘talking’ alarm to warn
when doors are left open and buzzers to warn when CO 2
levels are high. Open doors and high CO 2 levels are also
indicated on the monitor of the Guardian Controls PMS.
Entrance to the food market is directly from the basement
car park.
5
54
RACA Journal I March 2020
www.hvacronline.co.za