AERMEC NRA Serie Manual Instalación página 20

The heater(s) must work for at least 24
hours before the compressor start-up,
and in any case the temperature of the
oil bowl must be 10-15°C higher than
the room temperature.
WARNING
At least 24 hours before starting up
the unit (or at the end of each period
of prolonged inactivity) the unit must be
powered up, to allow the heaters of the
compressor carter to evaporate any
refrigerant that may be present in the
oil. If this precaution is not performed the
compressor could be seriously damaged
and the guarantee would no longer be
valid.
6. 1 .2 Hydraulic circuit
checks
- Check that all
connections are correctly made and
that the indications on the plates are
observed.
- Check that the hydraulic system is full
and under pressure, and check also
that there is no air (if there is air, bleed
it).
- Check that any interception valves on
the system are correctly opened.
- Check that the circulation pump(s) are
working, and that the water flow rate
is sufficient to close the flow switch
contact.
- Check the water flow rate, measuring
the difference of pressure between
the evaporator inlets and outlets,
and then calculate the rate with the
"Evaporator pressure drops" diagram
in the technical documentation.
- Check the correct working of the flow
switch: by closing the interception
valve at the heat exchanger outlet, the
unit must visualise the block. Reopen
the valve and rearm the block.
6.2 Start-up
After carefully carrying out all the checks
detailed above, it is possible to start
up the unit by pressing the ON button.
Check the set working parameters (set-
point) and rearm any alarms that may be
present. After a few minutes, the unit will
start up.
- Check the rotation direction of the fans.
If the rotation is not correct, switch off
18
the main power supply and invert two
of the three power supply cables on
the main switch. Do not tamper with
the connections inside the electrical
cabinet. Doing so voids the guarantee.
- Check the input current of the fans
and the compressor, and compare it
with the technical data in the technical
documentation.
NOTE
For the
parameters and for detailed information
regarding machine functioning and the
control card, refer to the user's manual.
6.2. 1
- Check for any refrigerating gas
leaks, especially near the pressure
the hydraulic gauge connection points, pressure
transducers and pressure switches
(vibration during transport may have
loosened the connectors).
- After a brief working period, check
the level of oil in the compressor and
the absence of bubbles in the liquid
indicator glass. The continuous passage
of vapour bubbles may indicate an
insufficient refrigerant charge or that
the thermostatic valve is incorrectly
set. The presence of vapour for brief
periods is, however, possible.
6.2.2 Overheating
Check the level of overheating by
comparing the temperature indicated
with a contact thermostat placed on the
compressor suction and the temperature
shown on the low pressure gauge
(saturation temperature corresponding
to the evaporation pressure).
The difference between these two
temperatures gives the superheating
value. Optimum values are between 4
and 8°C.
6.2.3 Under-cooling
Check the level of under-cooling by
comparing the temperature indicated
with a contact thermostat placed on
the tube at the condenser outlet and
the temperature shown on the high
pressure gauge (saturation temperature
corresponding to the condensation
pressure).
setting of all functional
Refrigerating circuit
checks
The difference between these two
temperatures gives the under-cooling
value. Optimum values are between 4
and 5°C.
6.2.4 Delivery temperature
If the values of under-cooling and
overheating are regular, the temperature
measured in the delivery tube
at the compressor outlet must be
30/40°C higher than the condensation
temperature.
6.3 Filling and draining the system
During the winter, if the system remains
idle, the water in the heat exchanger
may freeze, causing
damage to the heat exchanger itself, the
complete draining of the refrigerating
circuits and, sometimes, damage to the
compressors.
To avoid the risk of freezing, there are
three possible solutions:
- the complete draining of the water
from the heat exchanger at the end
of the season, and the refilling at the
start of the next season, by means
of the drain valve located on the
accumulation tank in the versions with
accumulation and/or pump ....
- the operation with glycol water, with a
glycol percentage chosen on the basis
of the minimum outside temperature
envisaged.
In this case, it is necessary to take
into consideration the different yields
and absorption of the chiller, the
measurements of the pumps and the
output of the terminals.
- the use of heaters in the heat
exchanger (standard on all devices).
In this case the heaters must always
be powered for the entire winter
period (machine in standby).
irreparable