Back to basics
ANDREW PERKS
Andrew Perks is a subject expert in ammonia refrigeration. Since undertaking his apprenticeship in Glasgow in the
1960s he has held positions of contracts engineer, project engineer, refrigeration design engineer, company director for
a refrigeration contracting company and eventually owning his own contracting company and low temperature cold
store. He is now involved in adding skills to the ammonia industry, is merSETA accredited and has written a variety of unit
standards for SAQA that define the levels to be achieved in training in our industry.
WHY USE AMMONIA INSTEAD
OF THE NEW RANGE OF HFCS
ON THE MARKET?
By Andrew Perks
I get asked this a lot, especially with the advent of ammonia plants becoming
major hazardous installations.
I
have news for you, a lot of HFCs have their own issues as
well so don’t tell me Ammonia is dangerous. It’s not just
about prime costs. What about the environmental impact?
Today we are caught up in global warming and climate
change issues. There are not many of the new refrigerants
that have zero impact. The natural refrigerants are the way
to go.
The other question is the supply and installation costs,
it really is horses for courses. We need to look beyond the
initial cost of things sometimes and consider the longer-term
investment and ongoing operational expenses. It’s not only
about the installation cost, but also about the longevity of
the equipment. It’s a well-known fact in the industry that
HFC systems are said to have an effective life span of 10
to 15 years, while ammonia is 30 to 40 years. Operating
efficiencies over these protracted periods are a prime
consideration.
With global warming we are seeing a marked increase in
ambient temperatures throughout the world. Considering
that the majority of HFC refrigerants are air-cooled
condensing systems, every degree increase in the ambient
temperature will push up the operating delivery pressure
which, yes you got it, will push up the absorbed power. More
demand for power results in the burning of more fossil fuel
which increases global warming resulting in higher levels of
CO 2 emissions and so the cycle escalates.
I think Greta Thunberg, a teenage Swedish environmental
activist got it right when she said, “What you are leaving
us – we will have to deal with the consequences of your
www.hvacronline.co.za
short-sightedness for generations to come.” A damning
indictment if ever there was one and it’s here right now. In
Australia they are looking at dry bulb temperatures between
45 and 48ºC.
With the push now on to use natural refrigerants the
ammonia industry is not being left behind. There has been
a serious move towards simplifying systems, reducing
their refrigerant charges, and improving overall equipment
energy efficiencies. There was a recent paper tabled in
Australia’s Climate Control News by Stefan James from
Scantec Refrigeration, where he spoke of a retrofit of an old
R404A refrigeration plant with a modern centralised, low
charge ammonia system.
With global warming we are seeing
a marked increase in ambient
temperatures throughout the world.
The energy efficiency improvements were measured to be
between 57 and 59% measured in kWh/m³ of cold room
volume. That’s without taking into account heat recovery
providing underfloor heating as opposed to electrical
elements which were retained due to the disruption and
costs to modify the freezer room floor. Jensen goes on
to state that the low charge ammonia system energy
RACA Journal I May 2020
65