T-CU11-OCT22-0
Page 10
Application Guidelines
The low-pressure safety cut out should never be set below the
settings as shown in the
THE SETTINGS MUST BE
ADJUSTED TO SUIT THE APPLICATION BEFORE STARTING THE
UNIT
.
Setting Procedure for Single Pressure Switch:
i.
Cut in range: Turning the range adjusting screw (4)
clockwise will decrease the cut-in pressure setting and
vice versa.
ii.
Differential range: Turning the differential adjusting screw
(5) clockwise will increase the differential pressure setting
and vice versa.
High Pressure Switch
Manual reset cartridge type high-pressure switch is integrated in the condensing unit to protect the compressor during
blocked fan or fan failure conditions. After fault is removed and high side pressure drops below 22barg, reset by
pressing the red button of the high-pressure switch.
Pump Down Recommendations
If pump down is used, the electrical circuitry should be arranged so that compressor
restart is triggered by demand from thermostat rather than a reset low pressure
switch.
The rotary/scroll compressor built in with a discharge valve to prevent high-pressure backflow into the low side. This
check valve prevents system pressures from equalizing and pump down could be achieved. However, there is potential
short cycling condition:
i.
If the low-pressure switch differentiate pressure is too close, the possibility of short cycling will increase. Refer
for the recommended settings to limit the short cycling.
ii.
If short cycling cannot be avoided for wiring where compressor restart triggered by low pressure switch, using
a 3-minute time delay will limit the cycling of the compressor to an acceptable level.
iii.
To eliminate the short cycling during defrost, the activation of compressor shall be triggered by demand from
thermostat.
Table 6: High- and Low-Pressure Switch Settings
Application Refrigerant
Low Pressure Settings bar(g) (Auto Reset)
High Pressure
Settings bar(g)
(Manual Reset)
Min.
Cut
Out
Factory Default
Pump Down System
(Recommended)
Cut in
Cut
Out
Cut
in
Differential
Cut in
Differential
MT
R404A/R448A/
R449A
1.5
3
1
4
2.5
22
28
