FEATURES
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cylinder (bottle) to the site. Calculating the size and number
of LPG cylinders required to ensure a sufficient flow of hot
water and establishing the pipe sizing requirements can
be a challenge, which is best left to trained and registered
LPG practitioners who are also competent in ensuring that
the entire installation complies with the various regulations
that cover LPG installations. Installations not undertaken by
such an installer could be potentially hazardous and may
not be covered by insurance companies.
HEAT PUMPS
Wil Jansen, divisional director of Alliance heat pumps,
explains more about the intricacies of heat pumps, with
input from the director of SARACCA, John Parry.
How it works
Parry explains that water heat pumps work on a
similar principle to air conditioners and chillers.
The refrigerant gas is compressed, condensed to
a liquid, expanded back to a gas and then back to
the compressor. In the process of condensing the
compressed refrigerant to a liquid, heat is rejected,
which is absorbed by the water in the condenser
heat exchanger. The liquid is then expanded before
it enters the evaporator (heat exchanger). Ambient
air is then drawn through the evaporator, removing
the cold air at approximately 8°C and ‘dumping’ it
into atmosphere. A heat pump replaces the electric
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elements of a geyser and uses a third of
the electricity.
The heat pump heats small quantities of water at a
time and recirculates it with the aid of a pump to and
from a tank (the geyser), heating the water gradually
until it reaches the desired temperature. The water
from the mains enters near the bottom of the tank
and the hot water exits at the top. An expansion relief
safety valve is also fitted on the tank. The temperature
in the tank that can be obtained from a heat pump is
approximately 55°C, but if higher temperatures are
required, electric elements can be installed in the tank
to raise it.
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Heat pump for
residential use.
Heat pump for industrial
use.
Heat pumps.
Heat pumps are
effective water heating
systems for schools.
Cost
Jansen admits that installation can be more expensive
than conventional electric geysers and solar geysers.
However, as with SWH, the payback period becomes
shorter as the electricity prices increase. A heat pump
can effectively save domestic and commercial users as
much as 70% of their geyser heating costs. Since the
Eskom rebate system stopped, there has been a definite
drop in the number of specialist heat pump installation
companies, but Jansen says there are several good
partners that have been “around the block” and know
their stuff, meaning there is growth potential in the
foreseeable future.
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February 2018 Volume 23 I Number 12