C6.2.27/0716-0219/E
15
5.5
Discharge temperature protection
5.5.1 ASTP Advanced Scroll Temperature Protection
Scroll compressor models ZB50KCE to ZB114KCE have the addition of the Advanced Scroll
Temperature Protection (ASTP). The Advanced Scroll Temperature Protection is also a
temperature sensitive thermo-disc that acts to protect the compressor from discharge gas
overheating. Once the discharge gas reaches a critical temperature, the ASTP feature will cause
the scrolls to separate and stop pumping although the motor continues to run. After running for
some time without pumping gas, the motor protector will open.
Figure 13: Advanced Scroll Temperature Protection (ASTP)
ASTP was developed to protect the compressor, not for envelope control. Applications where
compressors are used in the upper left corner of the operation envelope may lead to undesired
downtime and cut-offs for safety. Therefore the envelope needs to be controlled properly. For such
applications, it is strongly advised to install an additional external discharge thermostat.
To identify compressors with Advanced Scroll Temperature Protection, a label has been added
above the terminal box.
NOTE: Depending upon the heat build-up in the compressor, it may take up to two hours
for the ASTP and motor protector to reset!
5.5.2 Discharge line thermostat
The use of an external discharge thermostat is required for all ZF*K5E and ZB*K5E compressors
and a discharge thermostat is included in the standard delivery of all these models.
Internal
discharge
temperatures
can
reach
unacceptable values under some extreme operating
conditions (such as loss of refrigerant injection charge
or extremely high compression ratio). This could cause
compressor damage.
The ZF*K5E and ZB*K5E dedicated discharge
thermostat has a cut-out setting of 130°C ± 4K with
closing at 101°C ± 8K and should be installed
approximately 120 mm from the discharge valve outlet
(see
Figure 14
). In order to avoid improper functioning
due to false readings this thermostat needs to be
insulated (see "X" in
Figure 14
).
Figure
14:
Discharge
temperature
protection: recommended position
X
