9. Start up system, adjust charge size. Label
system for the refrigerant and lubricant used.
Start the system and let conditions stabilize. If
the system is undercharged, add Suva
®
HP62 or
Suva
®
507 in small amounts (still removing
liquid from the charging cylinder) until the
system conditions reach the desired level. See
the Pressure/Temperature Charts in this bulletin
to compare pressures and temperatures for the
Suva
®
refrigerant you are using.
Suva
®
refrigerants are more sensitive to charge
size than R-22. System performance will change
quickly if the system is overcharged or under-
charged. Sight glasses in the liquid line can be
used in most cases as a guide, but system charge
should also be determined by measuring system
operating conditions (discharge and suction
pressures, suction line temperature, compressor
motor amps, superheat, etc.). Attempting to
charge until the sight glass is clear may result
in overcharging the refrigerant. Please read
“How to Determine Suction Pressure, Super-
heat, and Subcool” below.
“Helpful Hints” For Retrofit From R-22
To Suva
®
HP62 or 507
Both Suva
®
HP62 and 507 have minimal “tempera-
ture glide” and can be used in systems that have
flooded evaporators and condensers, as well as those
that have direct expansion evaporators.
Since HP62 and 507 have higher cooling capacity
than R-22,at lower evaporator temperatures the
expansion device may need to be adjusted or re-
placed to maintain proper flow control and super-
heat settings. Estimated capacity comparison:
Evaporator Temperature Capacity
30 to 50°F (–1 to 10°C) Same
0°F (–18°C) +6%
–40°F (–40°C) +30%
Verify that compressor suction and discharge piping
is the proper size to maintain proper refrigerant
velocity and pressure drop.
Compressor discharge temperature will be lower
than R-22.
The compressor discharge pressure will be higher
with HP62 and 507. Various pressure switches may
need to be adjusted to maintain proper operating
conditions; for example:
• Evaporator pressure regulators
• Cut-in and cut-out pressure switches
• Condenser fan cycling pressure switches
• Head pressure controls
• Crankcase pressure regulators
• Others
Due to the higher oil miscibility with HFCs and
POE, verify proper compressor oil sump levels.
Check with the compressor manufacturer for proper
amperage load ratings.
Pressure/Temperature Charts
Introduction
How to Read the Pressure/Temperature
Charts
Tables 1 through 5 contain pressure/temperature
charts for the refrigerants discussed in this bulletin.
R-12, R-22 and Suva
®
134a are all single compo-
nent refrigerants with no temperature “glide” in
the evaporator or condenser. Suva
®
HP62 and 507
have very small glide (less than 1F [0.6C]). For
field service purposes, this glide can be neglected in
calculating superheat and subcool. The evaporator
temperature can be considered equal to the saturated
vapor temperature at the compressor suction pres-
sure; the condenser temperature can be considered
equal to the saturated vapor temperature or the satu-
rated liquid temperature at the compressor discharge
pressure. For Suva
®
HP62 and 507, the saturated
vapor temperatures are listed in the tables.
How to Determine Suction Pressure,
Superheat, and Subcool
Suction Pressure
Determine the expected evaporator temperature
using the R-12, R-502 or R-22 column (from the
baseline data you collected prior to the retrofit).
Find the same expected evaporator temperature in
the column for Suva
®
134a, HP62 or 507. Note the
corresponding pressure for this temperature. This
is the suction pressure at which the system should
operate.
Superheat and Subcool
Using the temperature column for Suva
®
134a,
HP62 and 507, the amount of superheat and subcool
is calculated in the same manner as for the CFC or
HCFC refrigerant.
Note: The amount of vapor superheat is always
calculated from the actual saturated vapor tempera-
ture; the amount of liquid subcool is always calcu-
lated from the actual saturated liquid temperature.
8
