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SERVICING
71
Mounting the condensing unit above the
evaporator coil will require oil traps at equal
intervals along the suction line. Install 1 oil trap
for a height difference of 15-25 feet between
indoor and outdoor units.
Install 2 oil traps for a difference
of 26-50 feet, 3 for 51-100 feet,
and 4 for 101-150 feet.
Fig 7. Oil Trap Placement
Long Radius Street Ell
45°
Street
Ell
45 °
Ell
Short Radius
Street Ell
Oil Trap Construction
Fig 8. Oil Trap
4. Low voltage wiring. Verify low voltage wiring size is
adequate for the length used since it will be increased
in a long line application.
Initial System Charging
R-410A condensers are factory charged for 15 feet of line set.
To calculate the amount of extra refrigerant (in ounces)
needed for a line set over 15 feet, multiply the additional length
of line set by 0.6 ounces. Note for the formula below, the linear
feet of line set is the actual length of liquid line (or suction line,
since both should be equal) used, not the equivalent length
calculated for the suction line.
Use subcooling as the primary method for final system
charging of long line set system application.
Extra refrigerant needed =
(Linear feet of line set – 15 ft.) x X oz./ft.
Where X = 0.6 for 3/8" liquid tubing
Remember, 3/8" liquid tubing is required for all long line
set applications.
Heat pumps should be checked in both heating and cooling
mode for proper charge level. This guideline is meant to
provide installation instructions based on most common long
line set applications. Installation variables may affect system
operation.
Follow the charging procedures in the outdoor unit I/O manual
to ensure proper superheat and sub-cooling levels, especially
on a system with a TXV installed in the indoor unit. Heat
pumps should be checked in both heating and cooling mode
for proper charge level. This guideline is meant to provide
installation instructions based on most common long line set
applications. Installation variables may affect system
operation.
NO ADDITIONAL COMPRESSOR OIL IS NEEDED FOR
LONG LINE SET APPLICATIONS ON RESIDENTIAL SPLIT
SYSTEMS.
S-202 DUCT STATIC PRESSURES AND/OR
STATIC PRESSURE DROP
ACROSS COILS
This minimum and maximum allowable duct static pressure
for the indoor sections are found in the specifications section.
Tables are also provided for each coil, listing quantity of air
(CFM) versus static pressure drop across the coil.
Too great an external static pressure will result in insufficient
air that can cause icing of the coil. Too much air can cause
poor humidity control and condensate to be pulled off the
evaporator coil causing condensate leakage. Too much air
can also cause motor overloading and in many cases this
constitutes a poorly designed system.
S-203 AIR HANDLER EXTERNAL STATIC
To determine proper air movement, proceed as follows:
1. Using a draft gauge (inclined manometer), measure the
static pressure of the return duct at the inlet of the unit,
(Negative Pressure).
2. Measure the static pressure of the supply duct, (Positive
Pressure).