C6.2.24/0215-0515/E
11
Figure 13: Wet v apour inj ection cycle for R407A & R407F low temperature applications
NOTE
: For Digital compressors ZFD13KVE and ZFD25KVE, the DTC valve bulb must
replace the existing NTC sensor located at the side of the compressor top cap. The
previous NTC sensor has to be removed and the controller, eg, ALCO EC3-D*, has to be
modified (disable discharge se nsor input). A new thermostat must be installed on the
discharge line. DO NOT use the previous solution NTC controller as a discharge
temperature protection since its rating is not suitable for R407A and R407F.
3.4 Discharge check valve
There is no discharge check valve at the discharge port of Copeland Scroll Digital compressors
ZBD21K* to ZBD57K* and ZFD13KVE to ZFD25KVE since the high-side pressure is needed to
support the operation of the unloader mechanism.
To avoid by-passing during the unloading process back to suction, a dynamic discharge valve is
fitted internally on the discharge port of the fixed scroll. This discharge valve cannot be used with
recycling pump down because it is not leak-proof during the off period.
Models ZBD58K* to ZBD114K* work with an internal unloader mechanism and are equipped
with a check valve in the discharge fitting that will prevent backward flow of gas through the
scroll when the compressor shuts off.
3.5 Brazing procedure
IMPORTANT
Blockage! Compressor breakdown!
Maintain a flow of oxygen-free
nitrogen through the system at very low pressure during brazing. Nitrogen
displaces the air and prevents the formation of copper oxides in the system.
If allowed to form, the copper oxide material can later be swept through the
system and block screens such as those protecting capillary tubes, thermal
expansion valves, and accumulator oil return holes.
Contamination or moisture!
Bearing failure!
Do not remove the plugs
until the compressor is set into the unit. This minimises any entry of
contaminants and moisture.
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