Table of Contents
Advertisement
•
Select a diameter and a velocity, and record the one
shown in the specified design conditions for the suction
or discharge line.
•
For the intersection point of the model number line with
the selected diameter and velocity run down vertically
to find out the pressure loss in kPa or psi for each 10 m
equivalent length (length in line metres plus accessories).
For other lengths the pressure loss is directly propor-
tional.
Verify that the suction line diameter is sufficent for the
discharge line.
Liquid line
The liquid line diameter can be selected using the table
below.
Table 6 - Liquid line diameter
Total equivalent length
Models
Up to 10 m
38UQZ 016 + 40ALZ 016
5/8"
38UQZ 020 + 40ALZ 020
5/8"
38UQZ 024 + 40ALZ 024
5/8"
•
For heights above 1 m it is recommended to subcool
the liquid line if the flow is ascending - subcool 1 K
for each 3,6 m in excess height. In this case add more
refrigerant.
•
Depending on the actual design calculate the equivalent
total line length. This is the sum of the linear metres
plus the sum of the equivalent metres of the accessories
(bends, valves, etc.).
•
From Table 6, select the liquid line diameter for the
model and the total equivalent length.
Liquid line requirements:
•
Do not insulate the liquid line, except where it is
exposed to the outside.
•
If the liquid refrigerant flow is descending and the
column height exceeds 10 m, a pressure-balancing valve
must be installed in the lower part to equalise the pres-
sures between this point and the higher liquid column.
If the height is more than 10 m it is recommended to
install a manual bypass control valve with a non-return
valve in the lower part of the vertical columns (see
Figs. and 6).
The manual control valve permits equalisation of the
pressures between the highest and lowest point of the
liquid column. Adjust the valve so that the pressure at
the expansion system inlet is the same as at the highest
liquid column point.
Control in cooling mode: The non-return valve permits
liquid flow when the refrigerant flow is ascending.
•
The pressure loss in the liquid line must not be higher
than 34 kPa ( psi).
•
In long lines it is advisable to install expansion bends.
•
The liquid line must not be isolated, except at the points
indicated above.
From 10 to 30 m
From 30 to 45 m
5/8"
3/4"
3/4"
3/4"
3/4"
7/8"
ATTENTION: Before connecting the refrigerant lines
carefully follow the steps below:
•
Remove the nitrogen holding charge from the refrige-
rant 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 38UQZ and 40ALZ units are supplied with a nitrogen
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 refri-
gerant 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- 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 refrige-
rant leaks.
Refrigerant R-407C consists of a non-azeotropic blend of
3% of R-3, % of R-1 and % 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 appro-
priate 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 quali-
fied personnel.
-
Refrigerant must never be discharged to the
atmosphere.
-
Use a refrigerant reclaim unit.
-
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.
3
Advertisement
Table of Contents
