88-A5HP5001-1B-EN 17
The Subcooling Charging method in cooling is not recommended below 55º F outdoor temperature.
The recommended method of charging at outdoor temperatures below 55º F is weighing in the charge. Return
when weather conditions permit charge verication through subcooling.
14.4 Subcooling Charging Below 55º F Outdoor Temp. (In Heating Only)
STEP 2 - Stabilize the system by operating for a
minimum of 20 minutes.
At startup, or whenever charge is removed or
added, the system must be operated for a
minimum of 20 minutes to stabilize before
accurate measurements can be made.
20 MIN.
STEP 1 - Determine additional charge.
Note: The nameplate charge value represents the amount of refrigerant shipped in the outdoor unit and is
compatible with 10 feet of AHRI rated refrigerant lines and the smallest AHRI rated coil.
Using the method below, find the charge associated with the additional length of tubing above 10 ft. and record it
below.
Weigh-In Method can be used for the initial installation, or anytime a system charge is being replaced. Weigh-In
Method can also be used when power is not available to the equipment site or operating conditions (indoor/outdoor
temperatures) are not in range to verify with the subcooling charging method.
STEP 1 - Measure in feet the distance between
the outdoor unit and the indoor unit and record on
Line 1. Include the entire length of the line from
the service valve to the IDU.
STEP 2 - Enter the charge multiplier (0.47 oz./ft for
3/8” and 0.30 oz./ft for 5/16”).
STEP 3 - Multiply the total length of refrigerant
tubing (Line 1) times the value on Step 2.
Record the result on Line 3 of the Worksheet.
STEP 4 - This is the amount of refrigerant to
weigh-in prior to opening the service valves.
.
1. Line length (ft) = ______________
2. Charge multiplier =
3. Step 1 x Step 2 = _____________
4. Refrigerant = _____________
for 3/8”, use 0.47 oz.
per foot and for 5/16”,
use 0.30 oz. per foot
Calculating Charge Using the Weigh-In Method
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