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ATTENTION: Before connecting the refrigerant lines
carefully follow the steps below:
-
Remove the nitrogen holding charge from the refrigerant
circuits.
-
Use silver alloy rod for soldering purposes, and ensure
that this work is done in a nitrogen atmosphere.
-
Check the pipes for leaks before welding the joint to the
unit pipes.
-
Once these connections have been made, carry out
another leak test.
REFRIGERANT CHARGE
The 38XTZ and 40ABZ units are supplied with an R-407C
holding charge. This must be removed before soldering the
connecting refrigerant lines to the unit. Once the soldering has
been completed, the complete refrigerant circuit must be
evacuated then the correct quantity of R-407C refrigerant for
each system must be charged.
WARNING: If any brazing is to be done the refrigerant circuit
must be filled with nitrogen. Combustion of refrigerant R-407C
produces toxic phosgene gas.
To evacuate and charge the unit with refrigerant, use devices
that are suitable and specific for refrigeant R-407C, used in
these units:
-
A pump for exclusive use with R-407C or with a non-
return valve in the R-22 pump.
-
Hose connections and pressure gauge jumper for R-407C.
-
R-407C cylinder in brown colour. Charging is always by
weight, using scales and a bottle. Only charge liquid
refrigerant.
-
Leak detection - it is difficult to detect R-407C refrigerant
leaks.
Refrigerant R-407C consists of a non-azeotropic blend of 23%
of R-32, 25% of R-125 and 52% of R-134a, and is
characterised by the fact that at the time of the change in state
the temperature of the liquid/vapour mixture is not constant. All
checks must be pressure tests, and the appropriate pressure/
temperature ratio table must be used for the interpretation of the
values.
Leak detection is especially important for units charged with
refrigerant R-407C. Depending on whether the leak occurs in
the liquid or the vapour phase, the proportion of the different
components in the mixture remaining in the unit is not the
same.
The following basic guidelines must be observed:
a)
Whenever there is a leak the complete refrigerant R-407C
charge that remains in the circuit must be removed.
b)
After the leak has been repaired, evacuate the circuit.
c)
Take into consideration that:
•
All leaks must be repaired immediately by qualified
personnel.
•
Refrigerant must never be discharged to the
atmosphere.
•
Use a refrigerant reclaim unit.
34
•
Any loss of oil from the system during maintenance
must be stopped immediately and the collected oil
must be removed in accordance with applicable
regulations.
d)
If, when the unit is run, symptoms of loss of charge (for
example, low pressure switch tripping or abnormally low
cooling capacities) are detected, first conduct a leak test
followed, if necessary, by a gas tightness test using
compressed nitrogen. For the latter all refrigerant must be
removed from the circuit. Transfer the refrigerant to a
storage tank and then clean the circuit as described earlier.
e)
Before adding the refrigerant charge proceed as follows:
-
Draw a vacuum in the refrigerant circuit until a
pressure of 667 Pa (-755 mm Hg) has been reached
for at least two hours. At a greater distance between
units the period must be longer. The period of time
of the vacuum is important.
-
Check that there are no refrigerant leaks.
Continue to charge refrigerant as described below:
Total charge = unit charge plus additional charge per metre
suction line and per metre liquid line.
-
The refrigerant charge for the 38XTZ and 40ABZ/ALZ
units is given in Table 1 - Physical Data.
For each metre of refrigerant connection line installed,
refrigerant has to be added in accordance with the table below:
Table 12 - Refrigerant charge (g/m)
Diameter
1/2"
5/8"
Liquid line
75
120
Suction line
14
23
OIL RECHARGE
If any oil needs to be added to fill the siphons and above all
when the total line length is high, use the same type and brand
as used in the compressors.
Compressor oil:
Type: 160PZ Maneurop-Danfoss (depends on the compressor
manufacturer).
3/4"
7/8"
1-1/8"
1-3/8"
180
250
420
645
34
47
81
123
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