Lighting
For work on AHU (maintenance and inspection work) is to provide adequate lighting.
Firefighting in case of fire
In general, the local fire protection regulations must be observed.
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If the AHU is part of the smoke extraction concept, then the specifications of
this concept have to be observed.
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Otherwise, the power supply of the AHU must be interrupted immediately at
all conductors. In addition, the dampers must be closed to consequently
prevent oxygen supply and fire spread.
Exposure to harmful substances in case of fire
In case of fire, some materials can produce noxious substances. In addition, harm-
ful vapours can escape from the unit. Therefore, severe respiratory protective
equipment is required and the danger zone has to be avoided.
Exposure to rotating parts / hot surfaces / electrocution
When working on AHU note the following risks:
Indentation of body parts in moving parts (belt drive, fan impeller, ...).
Burns and scalds on hot AHU components such as heat registers, heat exchangers,
...
Electrocution on current-carrying parts such as electric motors, frequency convert-
ers, electric heaters, control cabinets, interior lighting etc.
Therefore must be ensured prior working on the unit, that…
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all current-carrying parts, such as fan motors, valves, motors and electric heaters are discon-
nected from the power supply by using the repair switch (emergency stop) and that the switch
is locked in position 'off' in order to effectively prevent a re-activation during the work.
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the housing of the AHU interior lighting (can have separate supply) is not current-carrying.
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all moving parts, especially fan wheel, motor and heat wheel have come to a standstill; wait at
least 2 minutes after switching off before opening the doors.
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for maintenance of frequency controlled motors, a waiting time of 15 minutes is recommended
– time to break down the residual capacitive charge of the frequency converter.
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Remove the key from doors with door lock before entering in the casing of the AHU. Keep the
key out of reach of unauthorized persons.
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Check that the hot media supply such as steam is interrupted and all the heat registers, heat
exchangers, etc. are cooled to ambient temperature.
In case of standstill of the plant (e.g. power failure), the repair switch is always to
check. Only when it is in the off position and secured against unintentional restart,
appliance doors can be opened and work on the device can be carried out.
Start of the AHU
Be ensured after working and before the start that…
