18
M
INI
-S
PACE
EC I
NSTALLATION
, O
PERATION
AND
M
AINTENANCE
M
ANUAL
NOTE
Use high quality hoses, and ensure they are free of
defects and don’t leak. To achieve the low vacuum
that must be attained when evacuating the system,
you should use copper tubing instead of hoses if
possible. The use of short, large diameter hoses
helps reduce evacuation time.
1. After ensuring there are no leaks, relieve pressure and
evacuate the entire system while maintaining all the
solenoids open. Pull an initial vacuum of 1500 microns
or lower using the suction and discharge service ports.
NOTE
When pulling a vacuum, the Schrader valves will
unnecessarily restrict the openings, increasing the
evacuation time. It is recommended to remove the
Schrader valve cores with a Schrader valve removal
tool, and draw the vacuum through the port on the
removal tool.
2. If you cannot evacuate the system below 1500 microns,
close the vacuum pump isolation valve and perform a
rate-of-rise test by observing the standing pressure
over time. If the pressure rises slowly (up to 200 microns
in 15 minutes), the system still contains moisture that
needs to be boiled off. Proceed to step #5. If the pres-
sure rises rapidly up to atmospheric pressure (more
than 50 microns per minute), there is a leak that wasn’t
detected during step #2. In this case, troubleshoot the
entire system for leaks and repair them, then begin the
initial evacuation process again starting at step #3.
3. If no leaks are detected after the initial vacuum, release
the vacuum and pressurize the system with 2-3 lbs of
dry nitrogen. Allow the system to stand for two hours with
the dry nitrogen charge. This gives time for the moisture-
absorbing nitrogen molecules to disperse in the system.
4. After two hours, release the pressure, then turn on the
vacuum pump and evacuate the system a second time
down to 1500 microns or less. Close the vacuum pump
isolation valve and pressurize the system again with dry
nitrogen and allow the system to stand for two hours as
in step #5.
5. After two hours release the pressure. Turn on the vacuum
pump and complete the process of evacuating the
system, this time with a goal of achieving a 250 micron
vacuum or less. Close the vacuum pump isolation valve.
When you can hold the vacuum at 500 microns or lower
for at least 2 hours with no signifi cant rise in pressure,
the system is ready to charge.
6. Replace the Schrader valve cores if you removed them
during the evacuation steps. You may now introduce the
refrigerant charge through the schrader valves.
2.9.4.3
Refrigerant Charging Procedure
R410A refrigerant must be weighed in when performing
the charge. Refer to section 2.9.4, “Estimating Refrigerant
Charge” and calculate the estimated amount of refrigerant
needed for your system.
When charging a system using a blended refrigerant, it is
essential that the composition of the refrigerant is maintained.
To ensure correct composition, introduce the refrigerant
(R410A) into the system in liquid form rather than vapor form.
Cylinders which are not provided with dip tubes should be
inverted to allow only liquid refrigerant to charge the system.
Keeping the temperature of the cylinder below 85 °F will
help maintain the correct refrigerant composition while the
cylinder is emptied.
WARNING
If refrigerant gas is released in an enclosed area,
it may accumulate in low areas and near the fl oor,
displacing available oxygen. If a major leak occurs,
there is a risk of asphyxiation. In such case, the area
should be immediately evacuated and ventilated.
Personnel should remain away from the area until it
is determined to be safe.
2.9.4.3.1 Initial System Charge
Follow the step-by-step instructions below to charge systems
using R410A refrigerant. The initial charge will be performed
by introducing liquid refrigerant to the discharge side of the
compressor or an available liquid line port with the A/C unit
turned off.
1. Bleed air from hoses and break the vacuum by sup-
plying liquid refrigerant to the discharge port near the
compressor until the pressure is equalized. This holding
charge allows the low pressure switch to “hold,” enabling
the compressor to operate throughout the process of
charging the system.
2.9.4.3.2 Fine Tuning the System Charge
Once the initial charge is completed, add refrigerant to the
unit while it is running.
CAUTION
An adequate heat load must be supplied to ensure
a proper charge.
