Page 17
Operation and Maintenance
Envistar Top 04-21
DSET.220501.07.en
Continuous product development may give rise to specification changes without notice.
Cooling mode
The compressor carries out the work required to run the cooling process. The
evaporator is located in the supply air for the unit. The heat from the outdoor air
is taken up in this coil, thereby cooling the supply air.
The energy supplied to the cooling system from the evaporator and the com-
pressor leaves the unit via the condenser in the extract air.
It is important to ensure that the air volumes are above the specified minimum
flow on both the outdoor air and extract air side. The process cannot work if
these air volumes are not available.
Heating mode
The heating pump function takes the heat content of the extract air and reuses
it, supplying the same heat to the air handling unit’s supply air.
The extract air is the heat pump’s energy source. When the extract air meets the
extract air coil, it is cooled since the coil functions as an evaporator. From the
evaporator, the refrigerant moves to the compressor, where it is compressed.
The refrigerant then moves to the supply air coil, where the energy from the
extract air and the compressor is released. The energy remaining in the extract
air downstream of the heat pump is then recovered in the rotor.
These two recovery systems give a very high degree of efficiency.
Since the rotor requires less energy to run than the compressor system, this will
be in the first instance. The compressor will only start when the rotor’s energy
recovery is insufficient to heat the supply air.
Compressor
Power control takes place with a speed-controlled PM scroll compressor. In the
event of an increased power requirement, the frequency inverter will increase the
speed of the compressor.
Compressor protection
In the event of an alarm initiated by the control equipment or the safety circuit,
the compressor stops and an alarm indication is given. The alarm can be read
on the Climatix display or the Carel unit on the unit’s circuit board.
In the event of an alarm, correct the fault and then reset the alarm. If alarm trips
repeatedly, an authorised refrigeration service company must be called in.
The cooling/heating pump will primarily trip alarms for the following errors:
• High pressure in the system, manual reset on pressure control HP1
• Low pressure in the system
• Alarm from frequency inverter
Function
The reversible heat pump is interlocked across the ventilation unit. If any of the
fans stop, the cooling/heating pump will also stop. The unit will not start unless
the minimum flow is achieved. If a trim heater is installed, the minimum flow
must also be reached before start up is permitted.
