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Subcooling Charging Below 55º F Outdoor Temp. (In
Heating Only)
Table 35. Subcooling Charging Below 55º F Outdoor Temp. (In Heating Only)
The Subcooling Charging method in cooling is not recommended below 55º F outdoor temperature.
The only recommended method of charging at outdoor temperatures below 55º F is weighing in the charge in heating mode.
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.
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 (0.47 oz./ft for 3/8" & 0.30 oz./ft for
5/16"). 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.
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.
STEP 3 - Complete the "Total System Charge" chart rating label below and label located on the outside of the unit with a permanent marker.
Note: Complete the "Total System Charge" chart when final charging is complete.
a.
Charge added at Factory =
b.
Charge added at install =
c.
Total System Charge (a + b) = ___________________lb/oz
STEP 4 - Return to site for adjustment.
Important: Return in the spring or summer to accurately charge the system in the cooling mode with outdoor ambient above 55º F.
18-BC116D1-1B-EN
___________________lb/oz
___________________lb/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.
1.
Total Line length (ft) –10 ft _______________
2.
Charge multiplier = for 3/8", use .47 oz. per foot and for 5/16",
use .30 oz. per foot
3.
Step 1 x Step 2 = ______________
4.
Refrigerant (oz) = ______________
20 MIN.
31
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