12
Since the interconnection pipes are created on site, it is essential to clean and
evacuate the pipes and the indoor and outdoor units.
NOTE
Cleaning must be performed by circulating
nitrogen through the pipes of the system.
Cleanliness is extremely important because
it prevents dirt resulting from the installation
from getting inside the pipes and causing
problems later.
The access points are the service
valves on the outdoor unit.
The valves leave the factory in the closed position
to keep the refrigerant in the outdoor unit.
To perform the evacuation, keep the valve in
the closed position and connect the manifold
hose to the valve and the other end to the
vacuum pump.
It is recommended to proceed with the
evacuation of the two connections of the
service valves simultaneously.
The range to be reached must be located
between 250 and 500 microns.
ATTENTION !!!
Never load liquid into the suction service
valve. When you want to do this, use a
service valve for the expansion pipe.
IMPORTANT !!!
5.3
Adjusting the Gas Load
To adjust the refrigerant load in the machines, superheat can also be used as a
perimeter. (Consider a range of 5 to 7
o
C)
SUPERHEAT
1.
Definition:
Difference between the suction
temperature (Ts) and the saturated
evaporation temperature (Tes).
SA = Ts - Tes
2.
Measuring equipment required:
• Manifold.
• Bulb thermometer or electronic thermometer
(with temperature sensor).
• Insulation tape or foam.
• Pressure - Temperature conversion
table for R-22.
3.
Measuring steps:
1
o
- Bring the bulb or sensor of the thermometer
into contact with the suction pipe 15cm
from the intake of the condenser. The
surface must be clean and the measurement
is performed on the upper part of the
pipe to prevent incorrect readings.
Cover the bulb or sensor with foam to
insulate it from the ambient temperature.
2
o
- Install the manifold on the suction
pipe (low pressure gauge).
3
o
- Once the operating conditions have
become stabilized, read the gauge
pressure of the suction pipe. Obtain
the saturated evaporator temperature
(Tes) by consulting the R-22 table.
NOTE
4
o
- Read the suction temperature (Ts)
shown on the thermometer. Take several
readings and calculate their average,
which will be the adopted temperature.
5
o
- Subtract the saturated evaporation
temperature (Tes) from the suction
temperature. The difference represents
the superheat.
6
o
- If the superheat is between 5 & 7
o
C, the
refrigerant load is correct. If it is below this
range, too much refrigerant is being injected
into the evaporator, and it is necessary
to remove refrigerant from the system.
If the superheat is high, too little refrigerant
is being injected into the evaporator, and
it is necessary to increase the refrigerant
in the system.
4.
Calculation example:
- Suction pipe pressure (pressure gauge)..75 psig
- Saturated evaporation temperature (table)..7
o
C
- Suction pipe temperature (thermometer)..13
o
C
- Superheat (subtraction)..........................6
o
C
- Superheat OK - correct load
Before starting to operate the equipment,
after adding the additional refrigerant load (if
necessary), open the service valves on the
outdoor unit.
ATTENTION !!!
Do not forget to purge the air from the
hose.
•
After creating the vacuum, add
positive pressure with R-22 so that
the vacuum is broken.
To proceed with loading the refrigerant, simply
keep the service valve in the factory position
(closed) and connect the manifold hose to
the valve (Schrader valve) of the service valve.