Back to basics
performance beats transcritical CO 2 systems by about 40%.
The low charge ammonia system envisaged has a gravity
feed plate heat exchanger incorporating a propylene glycol
loop for the medium temperature circuit. It incorporates
three compressors all mounted on a skid base. The unit
would be fully assembled and only require to be positioned
in place and connected to the evaporative condensing
circuit and a dry expansion high pressure refrigerant loop
supplied to the low temperature cold rooms. Variable speed
drives have been used throughout to ensure the maximum
efficiency of the system.
Reducing costs and ensuring maximum efficiency with
all engineering and the majority of the construction work
completed prior to deliver to site is a neat concept.
That said, the extra capital cost of the low charge ammonia
system when compared with the initial cost of a transcritical
CO 2 system should be returned in about four years based on
the energy savings. It should also be noted that the ammonia
system is reputed to have twice the effective life of a CO 2
system. This is significant when you look at the investment – a
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RACA Journal I May 2020
new low charge ammonia system to replace an existing HFC
system can be cash flow positive from day one. When we look
at the effect on operating costs of the energy savings it can
exceed the finance costs. Each project needs to be evaluated
on its own particular merits but with the projected savings in
operational energy costs, the balance sheet should show a
positive effect allowing further investment.
Assuming the client continues to use these savings
towards paying off his loan a new low charge ammonia
system could be paid off in 5 to 7 years, which makes it a win-
win situation.
Of course, this does not consider the current issues that
we have with HFCs as to which refrigerant is going to be
available in a few years, and the escalating refrigerants
costs. Ammonia has been around since 1834 and is the
cheapest refrigerant. I’m not sure what the longevity will be
with this current range of HFCs.
To quote Confucius “May you live in interesting times”. A
curse or a prediction!
Chat next month. RACA
www.hvacronline.co.za