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Operation and Maintenance
Envistar Flex
DSEF191101.05.EN
Continuous product development may give rise to specification changes without notice.
6.5 Run-around coil unit (code EXL)
The run-around coil unit is used to recover heat from the extract air and trans-
fer this heat to the supply air for reduced energy use. The run-around coil unit
consists of the extract air coil with drip tray and the supply air coil (heating coil)
mounted in the casing.
Moisture precipitation in the extract air’s heat recovery coil entails a risk of
freezing and possibly frost/ice forming. This freezing is counteracted by installing
and connecting a freezing sensor that controls the valve actuator (liquid flow) in
the extract air coil.
The coils will have impaired capacity if dust forms a coating on the coil surfaces.
Not only does this impair the heat transfer capacity of the coil, it also increases
the pressure drop on the air side. Even if the ventilation system is fitted with
high quality filters, as time passes dust deposits will form on the front edges of
the coil fins (at the inlet side). To utilise its full capacity, the coils must be well
vented. The pipework should be vented by opening the bleeder screws in pipe
connections and/or an air vessel.
Inspection
DANGER!
Risk of serious personal injury and/or damage to air handling
unit.
Read and understand the entire chapter "1.5 General safety
messages" before working on, servicing, or inspecting the air
handling unit.
Check:
1. The coil fins to detect possible mechanical deformity
2. That the coils are not leaking
3. The drip tray and drain with water trap (clean if necessary)
4. That the water trap (without non-return valve) is filled with water.
