J&M CellarPlus 70-S1/S3, Technical Manual

Page: 14 / 32

Issue: 01.06.2023 Page 11
Ensure an adequate liquid charge has been
introduced to the high side of the system
before starting to ensure a minimum operating
pressure on the suction side of 0.5 bar is
maintained, otherwise overheating of the
scrolls and subsequent damage may occur.
Dual Pressure Switch
The dual pressure switch fitted to condensing units is auto
reset for low pressure side and manual reset for high
pressure (fixed differential) are
NOT factory preset for
application.
Figure 14: Adjustment on
Danfoss KP17WB
KP17WB has high pressure convertible reset feature. Insert
screwdriver into the slot on the lock disc and turn it to the
desired reset configuration as shown in
Figure 15 .
Do not turn the screw on the lock disc as it may damage the
convertible reset mechanism.
Figure 15: KP17WB: H igh Pressure Reset Option
When high pressure trip is changed to auto reset on
KP17WB, the compressor is ready to turn ON when
discharge pressure drops below the setting value of (Cut
Out
– Fixed Differential).
When HP switch cut out mode is changed
from Manual to Auto operation, the fitting of
an ART (anti-recycle timer) is recommended
to protect the compressor.
Table 9: Dual Pressure Switch Manufacturer
Setting
Model
High (barg) Low (barg)
Cut Out
Diff.
(Fixed)
Cut
In
Diff (adj)
KP17WB 18 4 3 2
Pressure Switch Settings
Both the LP and HP switch settings must be adjusted to
suit application before starting the unit.
Ensure that the
setting should be kept within the working pressure range
shown in
Table 10 .
High pressure safety
•
The high-pressure safety switch is required to stop the
compressor should the discharge pressure exceed the
compressor’s high side operating pressure.
•
The high-pressure switch can be set to lower values
depending on the application and ambient conditions.
Low pressure protection
•
The low-pressure protection cut out switch protects the
compressor against deep vacuum operation, a potential
cause of failure due to internal arcing and operating
outside the compressor limits.
•
The low-pressure protection cut-out should never be set
lower than the min. Low Pressure Cut Out value in
Table
10 . If the unit fails to pump down, the pump down
pressure should be reset to a higher value.
•
Care should be taken because the scroll sets will unload
at a pressure ratio of approximately 10:1. Thus, system
operating pressures should be kept within the range
shown in
Table 10 .
Table 10: Working Pressure (R448A/R449A)
Description Pressure (barg)
Min. Low Pressure Cut Out 2.0
Max. High Pressure Cut Out 27.7
Low Pressure Operating Range 2.0~7.1
High Pressure Operating Range 7.1~27.7
Service & Maintenance
Disconnect the mains electrical supply
before servicing or opening the unit.
The units are designed to give long life operation with
minimum maintenance. However, they should be routinely
checked, and the following service schedule is
recommended under normal circumstances:
1. Indoor and Outdoor units – Inspect at regular
intervals.
•
Check for refrigerant leaks on all joints and fittings.
•
Check mountings for tightness and wear.
•
Inspect pipework for any damage.
•
Check all electrical connections.
•
Ensure that no abnormal noise or vibration is detected
during the test run.
2. Condenser and Evaporator Fan Motors & Blades –
Clean and inspect at regular intervals.
•
Check for abnormal noise, vibration, and fan imbalance.
•
Ensure that the fan motors are clean and spin freely.
•
Check that the fan blades are clean and free from
restriction and damage/imbalance.