70
8024252/AE00/V1-0/2020-07| SICK
O P E R A T I N G I N S T R U C T I O N S | ZIRKOR200 Ex-D
Subject to change without notice
10
HEATING SHUTDOWN IN CASE OF MALFUNCTION
Fig. 40: Control unit Safe Area
Fig. 41: HCU LED opening
10.2
Functional description
The fail-safe heating shutdown can be used for heating shutdown when the limit
temperature of heaters is exceeded, especially of ATEX-certified O
2
probes.
The heating shutdown is permanently set to the temperature specified in the order code
(standard is 810 °C).
The temperature is measured by means of two type K thermocouples housed in a sheathed
thermoelement. The device has two independent channels. Each of these channels
switches a relay when the specified maximum temperature is reached.
The contacts of both relays are connected in series so that the heating is switched off when
the temperature in one channel is exceeded. The heating is also switched off when the
operating voltage is lost. Furthermore, the difference between the two channels is
monitored; the heating is switched off when the difference is more than 32 °C.
10.3
Maintenance
The heating monitoring is checked by the manufacturer before delivery.
The heating monitoring device must be returned to SICK for inspection at the latest by the
date noted on the calibration label (
see “Display and operating elements”, page 69
There is an opening in the front panel marked
“HCU LED”. The error LEDs can be seen through
this opening. The electronics must be reset when
a fault occurs. This is done by switching the
system off and on again.
19" rack
