instruction and operation manual ZHK NANO
46 / 116
V04-18
The control of the electric heater always takes place in such a way, that the air temperature after
the electric heater never exceeds the permitted air temperature in the unit (40 °C, if not differently
specified in the technical data). This item must be especially observed, when the air handling unit
is only operated with a partial air flow (e.g. in times of reduced use of the building).
As the heat output of an electric heater is provided very quickly and with ON-
OFF operation in the full amount, arises a significant risk of overheating the unit,
which results in damaging several components, especially when the unit is oper-
ated with low airflows.
For this purpose, the air handling is equipped with a supply air sensor, which directly measures
and monitors the air temperature generated by the electric heater. The control engineering is used
to ensure that the heating power of the electric heater is controlled so, that the temperature re-
mains within the permitted air temperature in the unit.
Avoid overheating of AHU components by residual heat of electric heater
In order to avoid excessive heating of components by residual heat of electric heater control en-
sures that fan motor keeps on running for at least 5 min after cut off of electric heater! By the use
of an enabling contact (see
Figure 87
) the control engineering also ensures, that the electric
heater can only start its operation when the fan is running.
If in case of main power failure (for example lightning stroke) this automatic run
cannot be ensured, AHU may become damaged by the residual heat of electric
heater.
In order to avoid damages, an uninterrupted power supply is recommended. If AHU is not operated
by an uninterrupted power supply after every main power failure an AHU inspection is requested
as indicated in
chapter 9 (Maintenance)
.
Safety concept
Electric heater power supply is equipped with 2 contactors in serial connection!
The 2 safety thermostats are connected such to protect the AHU both, by contactors in power sup-
ply and by software of control. In case of failure contactors must immediately cut off electric heater
from power supply
-
The 2 safety thermostats are connected in serial connection
-
The 2 safety thermostats are equipped with manual reset.
-
After triggering the reason for stopping must be detected and eliminated before reset of the
thermostat!
Thermostat 1 (Figure 84 and Figure 85)
-
Position of thermostat body: fastened on electric heater at connection side, accessible by re-
moving the electric heater access panel.
-
Triggering
temperature:
pre-set
±
value must not be changed.
-
Sensor
position:
between heating bars.
-
Function: alarm stop in case of over temperature because of low airflow.
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