Service manual

SERVICING
46
Installation Requirements
1. In a completely horizontal installation with a long line set
where the evaporator is at the same altitude as (or slightly
below) the condenser, the line set should be sloped
towards the evaporator. This helps reduce refrigerant
migration to the condenser during a system’s off-cycle.
2. For a system installation where the evaporator is above
the condenser, an inverted vapor line trap should be
installed on the suction line just before the inlet to the
evaporator (see Fig 6). The top of the inverted loop must
be slightly above the top of the evaporator coil and can be
created simply by brazing two 90° long radius elbows
together, if a bending tool is unavailable. Properly support
and secure the inverted loop to the nearest point on the
indoor unit or adjacent structure.
Fig 6. Evaporator unit with inverted vapor loop
3. An oil trap is required at the evaporator only if the
condenser is above the evaporator. Preformed oil
traps are available at most HVAC supply houses, or oil
traps may be created by brazing tubing elbows together
(see diagram below). Remember to add the equivalent
length from oil traps to the equivalent length calculation of
the suction line. For example, if you construct an oil trap
using two 45° elbows, one short and one long 90° elbow
in a ¾” diameter suction line, the additional equivalent
length would be 0.7+ 0.7+1.7+1.5, which equals 4.6 feet
(refer to table 9).
Long Radius Street Ell
45°
Street
Ell
45 °
Ell
Short Radius
Street Ell
Oil Trap Construction
Fig 7. 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.
System Charging
R22 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.
Extra refrigerant needed =
(Linear feet of line set – 15 ft) x X oz/ft.
Where X = 0.6 for 3/8" liquid tubing
Remember, for condensers with a liquid valve connection
less than 3/8" diameter, 3/8" liquid tubing is required for a
line set longer than 25 feet.
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-122 REVERSING VALVE REPLACEMENT
Remove the refrigerant charge from the system.
When brazing a reversing valve into the system, if is of
extreme importance that the tempo\erature of the valve does
not exceed 250° F. at any time.
Wrap the reversing valve with a large rag saturated with
water. "Re-wet" the rag and thoroughly cool the vavle after
each brazing operation of the four joints involved. The wet rag
around th reversing valve will eliminate conductin of heat to
the valve body when brazing the line connection.
The use of a wet rag sometimes can be a nuisance. There
are commercial grades of heat absorbing paste that may be
substitued.
After the valve has been installe,d leak test, evacuate and
recharge.