Start-Up Operations - Profroid SOLO 25 Handbuch

Refrigeration network connection
General information
BEFORE ANY WORK IS DONE ON THE REFRIGERATION CIR-
CUIT, THE HOLDING CHARGE MUST BE REMOVED (NITRO-
GEN).
Connection to suction
The pipe diameters must be determined in advance to ensure cor-
rect oil return and should not be based on the diameters of the col-
lector suction valves.
The piping should always fall towards the unit, never away.
For double models, the link between the two coils should be made
on-site.
A return must always be provided at the cooler output with a siphon
and backflow.
Connection to liquid piping
This piping must be welded into the main liquid pipes from under-
neath.
The liquid solenoid valve must be positioned as close as possible
to the cooler whilst avoiding placing it in the water stream during
defrosting.
Connection of defrosting water
This must be installed with a siphon to the outside.
A heated flex must be provided on negative temperature units.
Selection of thermostatic expansion valve
The coolers are fitted with diaphragm distributors. The loss of char-
ge to be taken into account, including wires, is 2,5 bars.
The expansion valves must be exclusively external balancing for all
models fitted with a distributor. The external balancing piping must
be connected approximately 10 cm after the bulb.
When a MOP expansion valve is used, its MOP point must be at
least 10 K greater than the set point temperature for the chamber.
In cases of sub-cooled liquid supply (twin-stage compressors or
booster unit), it is essential that this parameter be taken into
account (temperature of liquid ~ 0 °C) when selecting the expan-
sion valve.
The risks run if this is not the case are: Expansion valve hunting
(oversizing), Hydraulic hammering.
This remark also applies to the solenoid valve which must be
systematically mounted with a thermostatic expansion valve.

Start-up operations

Preliminary checks
Ensure that all the threads are fully tightened on fans (jolting during
transportation could cause them to loosen).
Check also if there are any breaks in the piping. (breaks could
occur during transportation).
Leakage testing
Pressurise the whole system, including the cooler, using a neutral
gas (Nitrogen) with a (non-liquid, non-colorant) tracer at a minimum
pressure of 10 bars and at a maximum pressure below 20.5 bars,
isolating the LP (low pressure) switches.
Important: If the LP (low pressure) circuit is fitted with a safety
valve (e.g.: on the suction accumulator) the test pressure on that
part of the circuit should be approx. 20 % below the operating pres-
sure of this valve.
Thorough leakage detection using a suitable detector should be
carried out on the unit.
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Dehydration of circuits
This operation must be carried out with all valves open (including
solenoid valves) with connection to a vacuum pump of the HP and
LP sides.
The quality of drying should not be judged by the speed at
which the level of vacuum is reached but on the effective time
it is held (24 hours at 0.7 mbar is a good standard).
The total increase in pressure during that period should not be
more than 2.6 mbar.
The residual moisture in the system should be less than 20 ppm.
When the installation is under vacuum, an insulation check of the
motor should not be carried out nor should the compressors be
started before at least 1 bar of fluid pressure is reintroduced. (To
prevent motor windings damage).
Fan checks
Check that the fans are rotating in the correct direction, i.e. drawing
on the coil.
Check the fans rotating direction.
Measure the current absorbed by each motor and compare with
the nominal current (displayed), taking into account the network
current.
Heater checks
Check heating
Ensure that the currents passing through the three phases are
identical and that there has not been an imbalance in the circuit. If
so, re-balance the circuit or replace the non-working heaters.
Heater insulation
Allow the heaters to warm up.
Cut off supply to these and very quickly take the insulation value on
the heater contactor between the phase and earth.
If this is over 3 K ohms when hot, it is satisfactory. If not, check
where the breakdown of insulation is, or for deficient heaters.
Defrost control
Air defrost
Sequences:
1. Stop compressor, while keeping the fans running by means of
the timer or the controller, preferably following a pump down to
drain the air cooler, but without creating a vacuum (the vapour
acting as a conductor in a vacuum).
2. Keep fans running during the full defrost
3. Return to cooling by means of timer or control switch.
Electric defrost
Sequences:
1. Stop compressor and the fans by means of the timer or the
control switch but preferably after a pump down to drain the air
cooler, but without creating a vacuum (the vapour is conductor
in a vacuum). Allow the heaters to warm up.
1.1 The heaters are controlled by a Defrost Termination Thermostat
(when ambient air temperature has been reached).
Cooling is restarted by the position of the thermostat bulb which
detects the pre-set temperature which must not exceed 10 °C.
The most suitable point on the coil is to be used at frost level.
The clock or controller acts as a safety device for restarting
cooling, if this is not done by the thermostat.
1.2 The heaters are controlled by a Limiter Thermostat (when
ambient air temperature has been reached).
Cooling is restarted by timer or controller reaching its time limit.
The bulb is positioned at the top of the coil, on the injection
side in a free space. Insert the bulb as far as possible. In this
case, the pre-set temperature will be from 7 °C to 9 °C with a
minimum differential (2 K)
As the thermostat operates the heaters during defrost, the coil
temperature evens out, which allows vapour production to be
reduced.