CG-SVX039C-GB
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BPHE Evaporator Maintenance
The Trane Model CGAF / CXAF chiller and Heat Pump
uses a brazed plate heat exchanger (BPHE) (or) a Shell &
tube evaporator with factory installed flow switch that is
positioned in the evaporator water pipe. The evaporator
inlet also includes a water strainer that must be kept in
place to keep debris out of the evaporator.
Note: Strainer maintenance is critical to proper operation
and reliability. Any particles larger than 1.6 mm entering
the BPHE evaporator may cause the evaporator to fail,
requiring replacement.
Acceptable BPHE evaporator water flow rate is 1.4 to
4.2 l/ min per nominal unit kW capacity. To maintain
12-7°C in/out chilled water temperatures, the nominal
water flow rate is 2.8 l/min per cooling kW.
Minimum water flow rate must be maintained to avoid
laminar flow, potential evaporator freezing, scaling and
poor temperature control.
Maximum water flow is 6 m/s. Flow rates greater than
this will cause excessive erosion.
The BPHE evaporator is difficult to clean should it
become plugged with debris. Indications of a plugged
BPHE evaporator include “wet” suction due to lack of
heat exchange, loss of superheat control, discharge
superheat less than 35°C, compressor oil dilution and/or
starvation and premature compressor failure.
BPHE Evaporator replacement
If the CGAF / CXAF BPHE evaporator requires
replacement, it is very important that the new evaporator
be replaced correctly and with the correct refrigerant and
water piping connections. The refrigerant inlet/ liquid
connection is at the bottom of the evaporator and the
refrigerant outlet/ suction connection is at the top of the
evaporator and both are on the same side. Pay particular
attention to evaporators with dual circuits. Avoid cross-
circuiting when installing the new evaporator.
BPHE Evaporator Maintenance
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