036-21323-002-C-0206
Unitary Products Group
11
REFRIGERANT PIPING
GENERAL GUIDELINES
Many service problems can be avoided by taking adequate
precautions to provide an internally clean and dry system and
by using procedures and materials that conform with estab-
lished standards.
Use hard drawn copper tubing where no appreciable amount
of bending around pipes or other obstructions is necessary.
Use long radius ells wherever possible with one exception -
small radius elbows for the traps in all vapor risers. If soft cop-
per is used, care should be taken to avoid sharp bends which
may cause a restriction.
Pack fiber glass insulation and a sealing material such as
permagum around refrigerant lines where they penetrate a
wall to reduce vibration and to retain some flexibility.
Support all refrigerant lines at minimum intervals with suitable
hangers, brackets or clamps.
Insulate all vapor lines with a minimum of 1/2” ARMA-FLEX
or equal. Liquid lines exposed to direct sunlight and/or high
temperatures must also be insulated.
Never solder vapor and liquid lines together. They can be
taped together for convenience and support purposes, but
they must be completely insulated from each other.
LINE SIZING
When sizing refrigerant lines for a split-system air conditioner,
check the following:
1.
Suction line pressure drop due to friction at full capacity,
2.
Liquid line pressure drop due to friction at full capacity,
3.
Suction line velocity for oil return at part capacity, and
4.
Liquid line pressure drop due to static head.
NOTE:
Never base refrigerant line sizes on the OD of the
suction and liquid connections on the unit.
Tables 13 and 14 list friction losses for both the suction and
liquid lines on the system. Table 12 shows the amount of
refrigerant charge required per foot of refrigerant line.
When the evaporator coil is below the condensing unit, the
suction line must be sized for both pressure drop and for oil
return. For certain piping arrangements, different suction line
sizes may have to be used. The velocity of the suction gas
must always be great enough to carry oil back to the com-
pressor.
When the condensing unit is below the evaporator coil, the
liquid line must be designed for the pressure drop due to both
friction loss and vertical rise. If the total pressure drop
exceeds 40 psi, some refrigerant may flash before it reaches
the thermal expansion valve. This flashing will not only cause
erratic valve operation and poor system performance, but
could also damage the expansion valve.
TABLE 12: REFRIGERANT LINE CHARGE
1
1. Charges are based on 40°F suction temperature and
105°F liquid temperature.
Refrigerant Line
2
2. Type “L” copper tubing.
Line Size
O.D. (in.)
Refrigerant
Charge (lb./ft.)
Liquid
5/8
0.113
Vapor
1-1/8
0.013
1-3/8
