System Charging; Dx Charging Requirements; R407C Refrigerant; Preparing System For Charging - Trane TR-OHS RCU Series Installation, Operation And Maintenance Manual

System Charging

DX Charging Requirements

When performing the specific DX charging procedures in
this section, follow these best practices:
• Ensure that contamination of different refrigerants
does not occur when using charging equipment.
Hoses or lines must be as short as possible to minimize
the amount of refrigerant contained in them.
• Keep cylinders upright.
• Ensure the refrigeration system is grounded to Earth
before charging the system with refrigerant.
• Label the system when charging is complete (if it is not
labeled already).
• Exercise extreme care to avoid overfilling the
refrigeration system.
Before recharging the system, it must be pressure tested
with oxygen-free nitrogen (OFN). The system must be leak
tested upon completion of charging but prior to
commissioning. A follow-up leak test must be carried out
prior to leaving the site.

R407C Refrigerant

R407C are blended refrigerants recognized for being safer
for the environment. These refrigerants contain no
chlorine, the component in HCFC's that destroy the earth's
ozone layer. However, the same care should be taken to
prevent leakage because R407C can contribute to the
greenhouse effect if released. If the refrigerant gas is
released in an enclosed space, it can become a suffocant.
Refrigerants that are multi-component blends have
component parts with different volatilities that result in a
change in composition and saturation temperature as
evaporation and condensation occur. Typically, the
composition of R407C vapor is different than that of R407C
liquid within a contained system. The composition of
liquid R407C refrigerant remains relatively constant,
however, the refrigerant vapor tends to separate into its
component parts even when circulating.
SS-SVX004C-EN

Preparing System for Charging

Note: Refrigerant charging must be performed by a
journeyman, refrigerant mechanic or an air
conditioning technician.
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 (liquid, suction or discharge lines
and reheat coil).
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 indicates a leak in
the system that needs to be repaired. After the system
is determined to be free of leaks, 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.
Notes:
• Use a vacuum pump 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.
• 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 and hot gas reheat valves open. Pull an
initial vacuum of 150 microns or lower using the
suction service port, the discharge service port after
the check valve and the service port of the receiver (if
applicable).
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 core removal tool and
draw the vacuum through the port on the removal
tool.
Installation
15