Compressor by Danfoss
 We're
looking at the North American model of the Prometeia Mach II GT, and at its heart is a Danfoss NF9FX refrigeration compressor.
Officially intended to run with R134a refrigerant, the Danfoss NF9FX draws up
to 310W of power during peak operation and is rated to work in ambient
temperatures up to 43°C.
At the front of the Mach II GT, you can see the small condenser
which is actively cooled with a 120mm Panaflo FBA12G12M fan, also known as the Panaflo
'Medium' fan to enthusiasts. This 120mm fan spins at 2100RPM while pushing 86.5CFM of air
with 35.5dB of noise.
The air
from the intake fan passes through the heat exchanger to cool down the refrigerant, it then passes by the compressor before being
exhausted from the rear of the enclosure by another Panaflo FBA12G12M. This fan has its own
wire guard, which is a great addition since there are quite a few wires in close proximity.
The intake Panaflo fan and heat exchanger.
Just below the rear exhaust fan we find the Mach II GT's
chip controller and control circuitry. As mentioned earlier, the Prometeia Mach
II GT can connect to the host PC via USB, and this allows the user to adjust
many of the cooler's characteristics using the included software program. We'll
touch base on the software in a minute.
Advantages of R404a over R134a
Refrigerant
The
Prometeia Mach II GT is charged with R404a refrigerant, which is a blend of
non-flammible Hydrofluorocarbon (HFC) gasses Pentafluoroethane /
1,1,1-Trifluoroethane / 1,1,1,2-Tetrafluoroethane. R404a is a near-azeotropic
'zero ozone depletion' HFC refrigerant specifically used for low-temperature
refrigeration applications. The term Azeotropic
describes "a liquid mixture of two
or more substances that retains the
same composition in the vapor state as in the liquid state when distilled
or partially evaporated under
a certain pressure." The boiling point at 1ATM pressure of R404a is -46.5°C, whereas the boiling
point for R134a is -26.1°C. Vapour pressure at 20°C for R404a is 167.2 PSIG, and
for R134a it is 84 PSIG.
The
original Mach I/II/II ST models ran with R134a, so the switch from R134a to
R404a essentially means that the Prometeia Mach II GT can attain lower evaporator (cold
head) temperatures and shorter start-up times. The trade off
being that the Danfoss NF9FX compressor has to work a little
harder. Compressor noise levels between the two refrigerants are no different, and the added
stress is apparently mitigated by changing the working pressure inside the Mach II
GT unit; 331 PSIG on the high side, 174 PSIG on the low
side.
ECT believe that the Danfoss
NF9FX compressor can run with R404a coolant in this very specialized application
without problems, and claim not to have had a single RMA case due to the change
from R134a to R404a.
Before
the Prometeia Mach II GT was released, the 'R404A mod' (as it is
known) was a common tactic amongst the higher echelon of enthusiast-overclockers. One of PCSTATS staffers had this mod done to a Prometeia Mach
I phase change cooler, recharging the compressor at a licensed HVAC service company
for about $230CDN, and that Mach I still runs well to this day.
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