PROJECT
27
The EESCO design team consisted of Andrew Lowe,
who is a qualified plumber, the owner Bruce Thomas
who has a background in commercial refrigeration,
and Shawn McRae who is the technical adviser.
“Beacon Road, which is now called ‘Elevate’, is a project that
was developed by Ithemba Property Development (alone)
for Divercity Urban Property Fund. The link to Jewel City is
that Divercity is also the landlord/owner of Jewel City, and
we think of all of these developments as part of a combined
investment in improving this part of the city,” says Carel
Kleynhans, Director: Ithemba Property Development.
Jewel City is a wider project which is changing the face of
Johannesburg’s CBD and revitalising several city blocks that
had been closed to the public for decades. This development
is a mixed-use and amenity-rich affordable housing precinct.
The Jewel City redevelopment initiative is a substantial
investment in Joburg by Divercity, a new investment fund
that is renewing and re-energising South Africa’s urban
centres with unique inner-city precinct development.
The system
The brief EESCO tendered on was to ‘heat 30 000l
from 15°C to 55°C in six hours in winter conditions of
0°C ambient temperature’, winter being the worst-case
scenario, according to Trinesh Chanka, a director at Izazi
Consulting Engineers.
“The original tender was for an imported ‘all-in-one’ type
heat pump that would have needed the evaporator cold air to
be ducted out of the basement. We proposed our alternative
locally manufactured hear pump. Our scope ended with the
plant, and the plumbing company (Plumbcon) took over from
there with the ring-main systems and sanitaryware,” says
Thomas. The system was installed in November 2019 and
the building has subsequently been populated floor by floor
and wing by wing.
“This is an indirect heating system, but our system is
different. There are other systems in the market which use a
stainless-steel coil dropped into the inside of a square tank
to heat the water. In our experience, that is an inefficient
means of heat transfer. With our more modern doublepass
brazed plate-heat exchanger. The efficiency is up to
about 98%, because of the greater amount of contact area
between the two mediums,” says Thomas.
The holding tank and pressure sets are designed to counter
the risk of dips in municipal water pressure, he says. “In
addition to the storage in the basement, there is storage up
on the roof so the complex is not reliant on municipal water
pressure but on its own system.
The hot water system itself is low pressure and unaffected by
water pressure, which is why we can have more economical
fibreglass tanks rather than steel pressure tanks.”
The three fibreglass tanks, 450kW heat pump and two 1 000kW
heat exchangers are located in a plantroom in the basement,
with a backup boiler (which has never yet been used). “The
R134 A refrigerant used in our heat pumps enable us to heat
water up to 80°C, which means you can use less storage (for
instance, 20 000l as opposed to 30 000l at 60°C). “Another
advantage of a plate heater exchange over a coil in a tank is that
we can locate the plate closer to the delivery point, and with that
higher temperature you can run smaller pipelines. Instead of a
two-inch pipe running 60°C water, for example, you could have
a 40mm pipe running 70°C water.”
Fresh water is pumped into the plate exchanger and once
it is heated is transferred up to the two separate ring main
feeds. The fresh municipal water is instantaneously heated
by the primary water stored in the thermal fibre-glass
storage vessels. The consulting engineers – Izazi Consulting
Engineers – made the choice to split it into two systems.
As to the saving, Thomas points out that compared to
the electric boiler back-up system it has, the savings are
expected to be on average 65%. A minimum of 50% in
winter and as much as 70% in summer.
“The three
fibreglass tanks,
450kW heat
pump and two
1 000kW heat
exchangers
are located in
a plantroom in
the basement,
with a backup
boiler (which
has never yet
been used).”
September 2020 Volume 26 I Number 07
www.plumbingafrica.co.za