18-AC115D1-1B-EN 21
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 verification through subcooling.
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 associ-
ated with the additional length of tubing above
10 ft. and record it below.
14.3 Subcooling Charging Below 55º F Outdoor Temp.
Calculating Charge Using the Weigh-In Method
1) Measure in feet the distance between the
outdoor unit and the indoor unit. (Include
the entire length of the line from the service
valve to the IDU.) Subtract 10 ft from this
entire length and record on line 1.
2) Enter the charge multiplier (0.6 oz/ft). Each
linear foot of interconnecting tubing requires
the addition of 0.6 oz of refrigerant.
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.
4) This is the amount of refrigerant to weigh-in
prior to opening the service valves.
1. Total Line length (ft) –10 ft ______________
2. Charge multiplier x ___0.6 oz _____
3. Step 1 x Step 2 = _____________
4. Refrigerant (oz) = _____________
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.
20 MIN.
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 mini-
mum of 20 minutes to stabilize before accurate
measurements can be made.
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