Product data

Long Line Applications – 38QRC & 38BK018/024 (continued)
7. Changes in piston size. The metering device for long line applications must be adjusted to compensate for the
frictional losses due to the long refrigerant lines, refrigerant line accessories, and indoor coils above or below
the outdoor unit. The AccuRater refrigerant metering device piston may need to be changed to provide this
adjustment. The AccuRater piston should be changed at the indoor or outdoor or both units depending upon
system configuration and line length. Use the Change in Indoor/Outdoor Piston Size for Elevation table #4 to
determine the correct piston size. The standard system’s piston size and locations are shown in the
Piston/Charge Combination Section.
a. Horizontal configuration: If the total equivalent horizontal length is 100 feet or longer, the piston must be
increased one full piston size, in addition to the charge change in step #10. If the exact size is not available,
use the next smaller size per Table #5.
b. Elevated Configuration: After finding the appropriate change in piston size add or subtract the change from
the original piston size number. If the piston size is decreased, round down to the next common piston size.
If the piston size is increased, round the new pistons size up to the next common size.
8. Liquid line solenoid and tubing configuration. The solenoid has a flow arrow stamped on the valve body.
When the valve is closed (not energized) and pressure is applied in the direction of the flow arrow, complete
shut off will occur. If pressure is applied against the direction of the arrow, leakage through the valve will
occur. When determining the proper location for a solenoid in a system liquid line, consider both flow direction
and location of the valve in the system. See Diagram #1thru #4 for proper location and install as follows:
a. Horizontal configuration Diagram #2
1. Install a biflow liquid line solenoid valve within 2 feet of the condenser with the flow arrow pointing
toward the outdoor unit if equivalent feet of piping is 100 feet or more.
2. Slope the vapor line toward the indoor unit to provide for refrigerant migration protection during the
off cycle due to temperature differences caused by slight elevation changes between indoor and
outdoor units.
NOTE: When installing a liquid line solenoid, a low voltage transformer may be required.
b. Elevated configuration: (Lift) Indoor unit above outdoor unit Diagram #3
1. A biflow solenoid valve is required in the liquid line within 2 feet of the outdoor unit with the flow
arrow pointing toward the heat pump unit.
2. The maximum elevation difference is 65 feet and the maximum equivalent length of piping is 200 feet.
3. Install an inverted trap in the vapor line. The top of the trap must be above the top of the indoor unit.
This prevents the refrigeration from collecting in the vapor line.
c. Lowered configuration: (Drop) Indoor unit below outdoor unit Diagram #4
1. For lines with less than 25 feet of drop, no solenoid valve is required in the liquid line. For lines with
over 25 feet of drop, install a biflow solenoid valve in the liquid line within 2 feet of the condenser
with the arrow pointing toward the outdoor unit.
2. The maximum elevation difference is 150 feet for and the maximum equivalent length of piping is 200
feet.
9. Additional Charge: The unit should be charged by weighing in the appropriate amount of refrigerant. Add
charge based on the additional length of line which is over 25 feet. Add 0.58 oz of refrigerant for every 1 foot
increase over the 25 feet. See Piston/Charge Combination Section for standard charge at 25 feet of liquid line
length.
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