PROJECT
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block’s ‘secondary circuit’ via our imported ‘Alfa Laval’
double pass plate heat exchangers. The municipal water
enters the BPHE (Brazed Plate Heat Exchanger) at a design
pressure of four bar and incoming temperature of between
12°C and 20°C and is instantly heated via the highly
efficient ‘double pass’ unit, to the setpoint which is currently
58°C,” says Lowe.
“The primary heating circuit is a water / glycol mixture
which is heated to between 65°C and 70°C by our
locally manufactured heat pump via its BPHE condensing
component. The primary heating liquid is stored in three
8 000ℓ steel glass flake epoxy lined low pressure storage
vessels. The design pressure for the primary storage is
only two bar making these tanks more economical than the
standard four bar rated vessels. These storage vessels are
stored on ground level, the heat pump however has been
installed inside the roof plant room with a V-coil evaporator
installed alongside in the open air where it achieves
maximum heat absorption and has a lower noise impact.
“The reason for the ‘double pass’ type of heat exchangers
is so that we can get the lowest possible return temperature
from the primary loop. The lower the temperature of the
water entering our heat pumps condensing unit, the more
efficient the heat pump is – this is primarily due to the ‘de-
superheating’ of the refrigerant when it is condensed in the
heat exchanger. We can achieve water outlet temperatures
5°C to 7°C higher than the condensing temperature of the
refrigerant which further increases the efficiency of the
unit. The central heating plant is a more economical way of
providing the entire complex with hot water. The 320kW heat
pump is designed to heat 24 000ℓ of water twice a day in
seven hours when the ambient temperature is down at 8°C,”
says Lowe.
“The advantage of this alternative to a heat pump and tank
in each block is that there is only one plant room, which
uses less space and requires less maintenance. Then there
are the additional benefits of less power supply needed
for the entire complex and fewer main electrical cable
supplies. Such a system isn’t more commonplace only
because the concept isn’t better known in South Africa –
this is only the second time we have done this, and as far
as I know we are the only company doing this design. The
circumstances of the site were ideal for it. We previously
did the same concept at the Sierra Hotel in Randburg,
which was of a smaller scale.
A commercial heat pump installed at The Village, Bramley.
“The savings are huge, and the bigger a development the
greater the savings in electricity consumption. It’s a function
of more people, more water, more saving.”
The system was designed and recommended to the
developers by EESCO for the potential savings that could
be achieved. The design team consisted of Lowe, who is
a qualified plumber, the owner Bruce Thomas who has
a background in commercial refrigeration, and Shaughn
McRae who is the technical adviser.
The expected COP for the heat pump is between 2.5 and
4.5 depending on the ambient temperature.
One of the features of these heat pumps, primarily designed
by EESCO, is that the evaporator has been separated from
the condensing (heating) unit, which enables the product to
be positioned more-or-less anywhere, because one of the
issues with all-in-one type heat pumps is that sometimes
April 2020 Volume 26 I Number 02
Andrew Lowe, a qualified plumber at EESCO.
www.plumbingafrica.co.za