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Instruction Manual ZHK
92/140 V07-21.0
By using an enabling contact (see
Figure 194
) the control engineering also ensures that the elec-
tric heater can only start its operation when the fan is running.
WARNING!
If in case of main power failure (for example lightning strike) this automatic run-
ning cannot be ensured. The AHU could become damaged by the residual heat
of the electric heater.
Therefore, in order to avoid damages, an uninterrupted power supply is recommended. If the AHU
is not operated by an uninterrupted power supply after every main power failure, an AHU inspec-
tion is required as indicated in
chapter 9 (Maintenance)
.
Safety concept
Electric heater power supply is equipped with two contactors in serial connection!
The two safety thermostats protect the AHU in two independent ways:
Firstly: By hardware via contactors in the power supply.
Secondly: By software via controlling. In the event of failure, contactors can immediately cut off the
electric heater from the power supply.
-
The two safety thermostats are connected in serial connection.
-
The two safety thermostats are equipped with manual reset.
-
After triggering (the reason for stopping) must be detected and eliminated before the reset of
the thermostat!
Thermostat 1 (Figure 191 and Figure 192)
-
Position of thermostat body: attached on the electric heater at the connection side, is accessi-
ble by removing the electric heater access panel.
-
Triggering temperature: pre-set-value must not be changed.
-
Sensor position: between heating bars.
-
Function: alarm-triggered-stop in case of temperature levels exceeding set limits because of
low airflow issues.
Figure 191:
Thermostat with
cover cap on the reset button
Figure 192:
Thermostat with
uncovered reset button
Thermostat 2 (Figure 193)
-
Position of the thermostat casing: attached on the outside panel of AHU casing
-
Triggering temperature: set to 70 °C
–
value must not be changed
-
Sensor position: downstream of the electric heater in upper area of airflow
-
Function: alarm-triggered-shutdown in the event of temperatures exceeding set limits because
of lack of airflow
Cover cap on reset button
Reset button