Table 4.
Weight of R-410A refrigerant (lbs./100ft of type
L tubing)
Line Size O.D.
Liquid Line
Discharge Line
1/2
5.88
1.27
5/8
9.44
2.03
7/8
19.62
4.22
1 1/8
33.44
7.20
1 3/8
50.95
10.97
1 5/8
72.11
15.53
2 1/8
158.29
34.09
Installation
32
SS-SVX002B-EN
Example: Estimate the amount of R-410A refrigerant
required for each compressor circuit in a system
consisting of a 10 ton (TR-CFD-035-D2A) A/C unit,
connected with a 1/2 in. x 30 foot liquid line and 7/8 in. x 30
foot discharge line to a Model SCS-252-DSA dual circuit
condenser.
Circuit 1
+ A/C Unit (Circuit 1)
=
2.70 lbs
+ 1/2 in. Liquid Line: 30 x 5.88/100
=
1.76 lbs
+ 7/8 in. Discharge Line: 30 x 4.22/100
=
1.27 lbs
+ Condenser
=
3.20 lbs
Estimated Refrigerant Charge
=
8.93 lbs
(Round off to nearest lb = 9.0 lbs)
Circuit 2
+ A/C Unit (Circuit 2)
=
2.70 lbs
+ 1/2 in. Liquid Line: 30 x 5.88/100
=
1.76 lbs
+ 7/8 in. Discharge Line: 30 x 4.22/100
=
1.27 lbs
+ Condenser
=
3.20 lbs
Estimated Refrigerant Charge
=
8.93 lbs
(Round off to nearest lb = 9.0 lbs)
Preparing System for Charging
1. With all the system piping connections made, perform
a dry nitrogen leak detection test on the system. Using
dry nitrogen only, pressurize the system to 150 psig.
Ensure all service and solenoid valves are energized
open and that no part of the system is isolated from the
pressurized nitrogen.
2. Since there is no refrigerant in the system to detect at
this point, leaks may be detected by observing if there’s
been a change in the standing pressure after 12 hours.
A significant drop in pressure (>10 psig) indicates a
leak in the system that needs to be repaired. After the
system is determined to be free of leaks, you may
evacuate the system.
Evacuate The System
NOTICE
Compressor Damage!
A proper vacuum must be drawn on the refrigerant
system to remove moisture prior to charging. If this is
not done the refrigerant charge will combine with
moisture in the pipes to form an acid that will
eventually lead to compressor failure. A triple
evacuation procedure with dry nitrogen is
recommended especially for systems with newly
installed refrigerant piping.
Note:
A vacuum pump should be used that is capable of
evacuating the entire volume of the A/C system,
including newly installed or existing piping. It is
essential to use a well-maintained pump that is in
good operating condition. Always ensure it
contains clean, fresh oil. Manufacturers
recommend you change the oil in the pump
regularly to maintain its ability to remove moisture.
Note:
Use high quality hoses ensuring they are free of
defects and don’t leak. It is recommended to use
copper tubing instead of hoses if possible due to
the low vacuum that must be attained when
evacuating the system. The use of short, large
diameter hoses helps reduce evacuation time.
3. After ensuring there are no leaks, relieve pressure and
evacuate the entire system while maintaining all the
solenoids open. Pull an initial vacuum of 500 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. During the evacuation process 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.
4. If you cannot evacuate the system below 500 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) it indicates moisture is in the
system that still needs to be boiled off. Proceed to step
#5. If the pressure rises rapidly up to atmospheric
pressure (more than 50 microns per minute) it
indicates 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.
5. 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
nitrogen molecules to disperse in the system
absorbing moisture.
6. After two hours, release the pressure. Then turn on the
vacuum pump and evacuate the system a second time
