ZX Platform Condensing Unit
10
OUTSIDE
INSIDE UNIT
End of tube
During brazing
protect housing with
damp cloth
During brazing
pull back fire
insulation
Start Up and Operation
Before commissioning, ensure that all valves on the condensing unit are fully opened.
Evacuation
The evacuation procedure is based upon achieving an actual system vacuum standard and is not time dependent. Before the
installation is put into commission, it has to be evacuated with a vacuum pump. Proper evacuation reduces residual moisture to
50ppm. The installation of adequately sized access valves at the furthest point from the compressor in the suction and liquid lines
is advisable. To achieve undisturbed operation, the compressor valves are closed and the system is evacuated down to 0.3 mbar /
0.225 Torr. Pressure must be measured using a vacuum pressure (Torr) gauge on the access valves and not on the vacuum pump; this
serves to avoid incorrect measurements resulting from the pressure gradient along the connecting lines to the pump.
Charging Procedure
Refrigerant Charging Procedure
The scroll compressor design requires system charging as quickly as possible with liquid refrigerant into the liquid line. This will
avoid running the compressor under conditions where there is insufficient suction gas. Sufficient suction gas is available to cool not
only the motor but also the scrolls. Temperature builds up very quickly in the scrolls if this is not done. Do not charge vapor (gas)
refrigerant into the ZX Scroll unit. The suction service valve must not be fully closed at any time while the compressor is running. To
do so would cause damage to the compressor in the same manner as explained above. This valve is provided for ease of connection
and for the fitting of service gauges without removing the unit panel. It is recommended to charge the ZX unit with refrigerant via
its service valves. It is recommended to break the vacuum in the system with a partial charge of the refrigerant, before starting the
system. For charge adjustment, it is recommended to check the liquid sight glass just before the expansion valve.
Oil Charging Procedure
ZX CDUs are delivered with a full oil charge in both the compressor and the oil separator. The oil level should be visible in the compressor
sight glass. All systems will trap some oil and in some cases it may be necessary to add oil if pipes are long, if the vertical rise is high
and if the piping is not well designed. The oil level should be monitored carefully during commissioning, checked after 4 – 8 hours and
checked again after 24 hours of normal operation. The ideal oil level is between ¼ and ¾ sight glass level but if any oil is visible in the
sight glass the compressor can operate safely. If oil is not visible in the sight glass proceed as follows:
1. Perform a manual defrost on all evaporators simultaneously.
2. Operate the compressor (at 100% load for ZXD) for 5 minutes after defrost is complete. The unit will automatically tend to
operate (at 100% load for ZXD) after defrost as the evaporators recover their set-point temperatures.
3. Check that the oil level is at ¼ sight glass or higher but not over the top of the sight glass.
4. If oil is not visible add oil until the level reaches the ¾ sight glass level.
Brazing Recommendations
Maintain a flow of oxygen-free nitrogen through the system
at a very low pressure during brazing. Nitrogen displaces the air and
prevents the formation of copper oxides in the system. If copper oxidization is 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.
This minimizes any entry of contaminants and moisture.
•
Remove the liquid line connection cap.
•
Then remove the suction connection cap.
•
Open both valves midway. Care should be taken to avoid the holding
charge from releasing too quickly.
•
Be sure that tube fitting inner diameter and tube outer diameter are
clean prior to assembly.
•
Since both tubes are extended from the condensing unit housing,
we recommend insulating the housing by using a wet cloth on the
copper tubing.
•
Recommended brazing materials: a copper / phosphorous or copper
/ phosphorous / silver alloy rod should be used for joining copper to
copper whereas to join dissimilar or ferric metals, use a silver alloy
rod, either flux coated or with a separate coating.
•
Use a double tip torch.
Typical Values With Individual Values /-5
o
C
Note:
ZXL CDU is designed with vapor injection technology. The condenser liquid line temperature will be sub cooled by the vapor injection plate heat exchanger.
R22
Ambient
°
C
-15
10
13
21
21
25
30
-10
15
17
25
25
29
-5
20
22
29
29
33
0
26
26
33
33
37
R404A
Ambient
°
C
-15
13
18
21
24
28
34
-10
16
22
25
29
33
-5
20
26
29
33
37
0
23
29
33
38
42
