28 PROJECT
Most systems are a combined unit which creates the problem
that it cannot be located in a basement where it would
recirculate cold air unless expensive ducting is provided
which can also have an adverse effect on the heat pump’s
performance due to back pressure on the fans. “When you have
heavy tanks, as with the 30 tonnes we have here, engineers
don’t want to locate them on the roof where additional load
bearing costs would be incurred, but in the basement or ground
level. That’s the attraction of the split system: the tanks can go
in the basement with the heat pump, and the evaporators or ‘air
coil’ can go wherever there is better air supply, such as the floor
above or even the roof. Noise is another factor in placing the
plantroom in the basement.
The side panel on the left shows the building’s various return-leg temperatures; the panel
on the right shows primary (entering temperature) and secondary (leaving temperature)
water temperatures. The primary pumps run on Danfoss variable speed drives.
Custom designed and manufactured locally – one of the two 150kW evaporators installed
one level above the plant room at Jewel City.
Two Bitzer semi-sealed compressors are the main heating component of this 450kW heat
pump located in the basement.
“The noise from the coils is a major consideration, they cannot
be placed close to apartments. They must expel the cold air
to the outside, and so in this project they have been located in
the ground floor parking area.”
Features
The brazed plate heat exchangers (BPHE) operate by means
of two separate mediums (water) exchanging heat with one
another. Cold water (the secondary circuit) supplied from the
building’s pressure pumps enters the heat exchanger and
is instantaneously heated to 60°C. The hot water system
(primary circuit) is a closed loop which never gets consumed,
while the cold water after instantaneous heating goes on to
be used in the residential units, or returned from the building
to the system and re-heated to the required temperature by
the BPHE and recirculated. The heat exchanger is a doublepass
system which ensures that the return water – on the
primary side is returned to the thermal storage vessels at
as low a temperature as possible. The lower the entering
temperature of the water for the heat pump, the more
efficiently it operates.
“The heat pump was manufactured to our specifications by
SCM – a division of Metraclarck. We also use HC Heating
Centre in Johannesburg, and also manufacture our own units.
The software has been designed by us and the IP is ours.
These commercial heat pumps are based on commercial
‘Multiplex’ refrigeration systems and have a number of safety
features that other, more economical all-in-one types do not.
These include:
• Liquid Receiver – enables system to be serviced and
filters changed without loss of refrigerant
• Oil separator – ensures oil return to compressors
• Oil management – for systems with multiple
compressors; ensures all compressors oil levels are kept
at optimum
• Semi-sealed compressors – can be serviced and
repaired and typically last 10-20 years
• Variable speed drives – used on compressors and water
pumps – increases overall efficiency
A web-based monitoring panel enables EESCO to keep
tabs from its offices and respond timeously if anything goes
wrong. This system also monitors and meters the KWH used
to heat the water, the KL of hot water used and the water
temperature. Historical Graphs are available and managing
companies can easily access data such as cost per KL or
building delivery temperatures.
www.plumbingafrica.co.za @plumbingonline @plumbingonline @PlumbingAfricaOnline September 2020 Volume 26 I Number 07