Refrigerating Circuit Checks; Overheating; Under-Cooling; Delivery Temperature - AERMEC NRC Serie Manual Instalación

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/differential pressure switch by
closing the interception valve at the
heat exchanger outlet, the unit must
visualise the block. Reopen the valve
and rearm the block.
7.2 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
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 setting of all functional parameters
and for detailed information regarding
machine functioning and the control card,
refer to the user's manual.
7.2. 1 REFRIGERATING CIRCUIT
CHECKS
- Check for any refrigerating gas
leaks, especially near the pressure
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.

7.2.2 OVERHEATING

Check the level of overheating by
comparing the temperature indicated
with a contact thermostat placed on the
20
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.

7.2.3 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).
The difference between these two
temperatures gives the under-cooling
value. Optimum values are between 4
and 5°C.

7.2.4 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.
7.3 FILLING AND DRAINING THE
SYSTEM
During the winter, if the system remains
idle, the water in the heat exchanger
may freeze, causing irreparable 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 storage
tank in the versions with storage tank
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).