Product data

Refrigerant Lines – 38QRC & 38BK018/024
1. The 38QR & BK018/024 units are shipped with a holding charge of R-22 refrigerant.
2. All charges, line sizes, and capacities are based on the fan coil with the smallest charge and 25 feet of
refrigerant lines. For system charge see Piston/Charge Combination section. Add additional charge by weight
as necessary and check charge by the super heat method. For runs over 25 feet see Long Line Applications.
Note: For runs less than 25 feet, some of the charge may need to be removed to obtain the correct system
superheat. The minimum line length should be 8 feet.
3. Install a filter dryer in the unit’s liquid line. Use of a field supplied moisture indicator is also recommended.
4. Refrigerant lines should not be buried in the ground. If it is necessary to bury the lines, not more than 36”
should be buried. Provide a minimum 6” vertical rise to the service valves to prevent refrigerant migration.
5. The vapor line must be insulated. Use a minimum of ½” thick insulation. Closed cell insulation is
recommended in all long line applications.
6. Special consideration should be given to isolating interconnecting tubing from the building structure. Isolate
the tubing so that vibration or noise is not transmitted into the structure.
Long Line Applications
1. Liquid lines should be 3/8” only. DO NOT resize liquid lines for additional length.
2. When sizing vapor line, determine line length by finding equivalent feet of pipe. Equivalent line lengths equal
the linear length (measured length) of interconnecting vapor tubing plus losses due to elbows (see Fitting Loss
in Equivalent Feet for Elbows Table #2) If the number of elbows is not yet known, assume 50% additional
length for the equivalent length. In determining line size, be sure oil can be properly returned to the
compressor. Consult the Carrier Systems Design Guide for proper oil return recommendations. For line lengths
from 25 to 49 feet no special piping requirements are normally required. Adjust charge to required amount by
adding refrigerant per step #10 below.
For line lengths over 50 feet
3. A crankcase heater should be added to scroll compressor units (all non-scroll compressor units have standard
crankcase heaters). Crankcase heaters help prevent refrigerant migration to the compressor during the off cycle.
4. Accessory wind baffles are recommended.
5. Any time the equivalent line length is over 100 feet, a liquid line solenoid must be used. A liquid line solenoid
may also be required for vertical lift applications over 25 feet. See step #9 and locate the solenoid at the
outdoor or indoor unit as required.
6. The Effective Capacity Loss, Table #3 provides the estimated percentage of nominal cooling capacity losses
based on the standard required vapor line size versus what is selected for long line applications. Heating
capacity is not generally affected by long line applications
a. Select the desired vapor line size from Table #3 based on equivalent feet and desired vapor line size.
b. Subtract the nominal percentage loss from the unit cooling capacities.
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