Project
1 2
Some of the electrical wiring at the site . 1 and 2 . The fresh produce AHU and condensing units .
whether to repair the existing system as a ‘ quick-fix ’ and then replace the entire system the following winter , or replace the entire system now in a similar time frame to that which the costly repairs would take .
Additionally , the supermarket chain wanted the requirements of their latest specifications to be adhered to as far as possible . The supermarket chain also wanted the facility to , sometime in the future , control the air conditioning and to use it in some sort of dehumidification process . The subsequent upgraded controls included in the project would allow VMG to easily achieve this and would include off-site monitoring and control . So , the system can be monitored and controlled from anywhere and all data can be recorded and analysed at will .
Generally , with the advancement of technology , the heat load and checks against what is installed within a facility – and further making sure that the new heat load is correct , there is invariably a significantly lower requirement to what was originally installed – and with that , obviously energy savings , capex savings and operational savings . For this project , VMG ’ s heat load calculation ended with a 960kW system – a big difference from the estimated 1 400kW of the original system . And further , the new system uses about half the energy the original system did , and of course , absolutely no water ! Chillers were not considered for this installation replacement as variable refrigerant flow ( VRF ) systems provided a far more efficient solution and were immediately available . This equipment also forms part of this supermarket ’ s standard air-conditioning specification . Using readily available equipment , VMG quickly realised that indeed an entirely new plant could be installed in a slightly longer period than
repairing the existing installation . With an assurance that a new plant could be up and running by 22 December 2020 , the landlord gave the go-ahead .
The cooling towers that were on piers in the outside plant area of the building were removed . The piers were then adjusted , waterproofed , and used to create a platform to install the new VRF condensing units .
VMG selected the LG brand specifically because all the condensing units already meet coastal conditions – in other words black-fin coated condenser coils and the casings are very high spec – ( in fact you can ' t buy a lower spec unit for inland applications ). This saves having to do any additional corrosion treatment to units and was considered a big plus .
Again , in accordance with the supermarket ’ s specification , EC plug fans were selected as they offer huge savings , not just in running costs , but also maintenance costs . There are no belts to replace or adjust – besides that , this skill is one that has not survived well into modern times – some technicians just don ’ t know how to carry out the correct tensioning . Incorrect tensioning can accelerate wearing on bearings and create all sorts of other challenges .
The existing plant had two very large backward curved centrifugal fans ( see accommodating photos ). The outer shells were kept and essentially the new EC plug fans were mounted onto the casings . This itself generated further savings for the client as fan walls were not required . This also meant no need to modify the ducting because the ducting was already connected to the original fans .
The old coils were also removed and replaced . The LG electronic expansion valves ( EEV ) and controlling kits were added to the system . According to all participants to this
www . hvacronline . co . za RACA Journal I August 2021 35