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Vacuum PROCEDURE
Any system that has been exposed to the atmosphere must be properly
dehydrated. This is achieved with a proper vacuum procedure.
To achieve a proper vacuum, a VACUUM PUMP (not a
compressor) and a VACUOMETER are required.
The procedure is as follows:
• First of all, the access points to the system must be defined.
For both the low and high side, use the existing service
valves on the condensing unit, i.e. the high pressure switch,
connected to the smaller diameter pipe, and the low pressure
switch, connected to the larger diameter pipe.
• Once this is done, the system can be evacuated.
Basically, it can be done in two ways:
DILUTION METHOD
1. Turn on the vacuum pump and build up vacuum in the pump
(register 1 closed).
2. Open register 1 and let the system evacuate until it reaches at
least 500 mcron. To obtain the measurement, close register
1 and open register 2 and make the vacuum gauge feel the
system pressure. After reaching 500 mice, isolate the vacuum
pump and open register 3, letting the Nitrogen pass through
to break the vacuum. Isolate the Nitrogen tube.
3. Vent the Nitrogen through the connection between the copper
line and register 3.
4. Repeat the operation at least twice, making the third evacua-
tion in the last phase. At the end at least 200 mice should be
obtained.
!
WARNING
Never disconnect the copper tubing from register 3, simply
loosen the connection to purge the nitrogen.
To obtain an accurate vacuum value, isolate the vacuum pump
from the system by closing register 1 and waiting about 5 minutes
for an accurate measurement. If the value does not hold, the
system still has moisture or there is a leak. Always check all
connections (points 1, 3 and valves).
HIGH VACUUM METHOD
It is applied with a vacuum pump capable of achieving a vacuum of
less than 200 microns in a single evacuation. Proceed as follows:
1. Turn on the vacuum pump and then open register 1.
2. Subsequently, isolate the vacuum pump and open register 2.
3. When a value of less than 200 mecrons is obtained (try to
reach the lowest possible value), the vacuum procedure is
finished.
!
WARNING
The pump oil should be changed periodically to ensure vac-
uum efficiency.
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!
!
32
Vacuum / Refrigerant Charge
!
WARNING
Before charging the refrigerant, check the safety data sheet of
the refrigerant.
REFRIGERANT CHARGE
!
WARNING
After evacuating the system properly, close the manifold registers
and isolate the vacuum pump, vacuum gauge and nitrogen tube.
NOTE: To make the refrigerant gas charge replace the
nitrogen tube (Figure 23-24 ) with a refrigerant gas
tube.
1. Purge the hose connecting the tubing to the service valve.
2. Open the service valve that provides access to the re-
frigerant gas tube and then the manifold discharge port.
3. To properly charge the system, check the unit identification la-
bels for the amount of refrigerant gas to be added to the system.
4. With the system stopped, charge the liquid refrigerant gas
through the liquid line service valve (smaller diameter). To
assist you, use a scale (if a graduated tube is not used).
Wait at least 10 minutes before turning on the equipment.
5. Close the manifold discharge register, open the suction
register and with the system running complete the charge
with refrigerant gas in gas form (5% to 20% of the total).
6. Check on the scale the weight of the refrigerant gas
that was added to the system. If charging is complete,
close the manifold suction register, disconnect the suc-
tion and discharge hoses and close the pipe register.
7. The charging procedure is complete.
!
!
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