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5.8.1 Measurement Device
Set-Up
1.
With an R-410A gauge set, attach the high-
pressure hose to the access fitting on the liquid
line (small) service valve at the OD unit.
2. Attach the low-pressure hose to the access fitting
on the suction line service valve (large valve) at
the outdoor unit.
3. Attach a temperature probe within 6” [15.2 cm]
of the outside of the unit on the copper liquid line
(small line). For more accurate measurements,
clean the copper line prior to measurement and
use a calibrated clamp on temperature probe or an
insulated surface thermocouple.
5.0 SYSTEM START-UP AND REFRIGERANT CHARGING
Start Up
5.8.2 Preliminary Charging
by Weight
NOTICE:
Adjust the system charge by
weight for the linear length of the refrigerant line set.
For a new installation, evacuation of inter-
connecting tubing and indoor coil is adequate; oth
-
erwise, evacuate the entire system. Use the factory
charge shown in “Electrical and Physical Data” in
Section 3.2 of these instructions or on the unit data
plate. Note that the charge value includes charge
required for 15 ft. [4.6 m] of standard-size liquid
line without a filter drier.
Calculate actual charge required with the actual
installed liquid line size and length using:
1/4” [6.4 mm] O.D. = .3 oz./ft. [8.5 g/.30 m]
5/16” [7.9 mm] O.D. = .4 oz./ft. [11.3 g/.30 m]
3/8” [9.5 mm] O.D. = .6 oz./ft. [17.0 g/.30 m]
1/2” [12.7 mm] O.D. = 1.2 oz./ft. [34.0 g/.30 m]
Add 6 oz. for field-installed filter drier.
Charge Adjustment = (Line Set (oz./ft.) x Total
Length) – Factory Charge for Line Set
Example:
A three ton heat pump unit with facto
-
ry installed 3/8” liquid service valve requires 75
ft. of line set with a liquid line diameter of 1/2”.
Factory Charge for Line Set =
15 ft. × .6 oz. = 9
oz.
Charge Adjustment =
(1.2 oz. × 75 ft.) – 9 oz. =+
81 oz.
With an accurate scale (+/– 1 oz. [28.3 g]) or
volumetric charging device, adjust the refrigerant
charge based on the actual line set length. If the
entire system has been evacuated, add the total
calculated charge.
IMPORTANT:
Charging by weight is
not always accurate since the application can affect
the optimum refrigerant charge. Charging by weight
is considered a starting point ONLY. Always check
the charge by using the Charging Chart
and adjust as
necessary. CHARGING BY LIQUID
SUBCOOLING PER THE SYSTEM CHARGING
CHART MUST BE USED FOR FINAL CHARGE
ADJUSTMENT.
IMPORTANT:
R-410A is a blending
refrigerant of R-32 and R-125 (50/50). These two
refrigerants have different saturation curves and
therefore change state at different pressures and
temperatures. If charge is added to the system in the
vapor state, it is possible to have a disproportionate
amount of each part of the R-410A blend which will
cause unstable and inefficient operation. Therefore, it
is critical to add R-410A in the liquid form only!
5.8.3 Preliminary Charging
by Pressure (Optional)
1.
Following airflow verification and charge weigh-
in, run the unit for a minimum of 15 minutes prior to
noting pressures and temperatures.
IMPORTANT:
Indoor conditions as
measured at the indoor coil must be within 2°F
[1.1°C] of comfort conditions per the homeowner’s
preference.
NOTICE:
If the indoor temperature is above
or below this range, run the system to bring the
temperature down or run the electric heat/furnace to
bring the temperature up to within this range.
2. Note the Outdoor Dry Bulb Temperature, ODDB°
= _____°F [_____°C]. Unit charging is recommend
-
ed under the following outdoor conditions ONLY:
55°F [12.8°C] outdoor dry bulb and above
3. Locate and note the design pressures. The
correct liquid and vapor pressures are found at the
intersection of the installed system and the outdoor
ambient temperature on the Charging Chart located
inside the access panel cover.
Liquid Pressure: = ______psig; Vapor Pressure =
______psig
