035-18550-001-A-0902
12
Unitary Products Group
Oil return will be critical during:
1.
The cooling cycle when the outdoor unit is above
the indoor unit (detail 1 of Figure 6).
2.
The heating cycle when the indoor unit is above
the outdoor unit (detail 4 of Figure 6).
When the indoor unit is above the outdoor unit, the size
of the vapor riser must be reduced to 1-1/8" OD so that
the velocity of the refrigerant will be great enough to
carry oil up the riser during the heating cycle.
When 1-1/8" OD tubing must be used for the riser, the
maximum length for the vapor line will be greatly
reduced as shown in the following examples.
EXAMPLES:
#1 - 10 Ton System
89 feet of 1-3/8" OD, type “L” copper tubing
(89 feet x 2.8 psi/100 feet) . . . . . . . . . . . . . . . . 2.5 psi
Fitting* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.5 psi
Vapor Line Pressure Drop = 3.0 psi
#2 - 10 Ton System
29 feet of 1-1/8" OD, type “L” copper tubing (vertical)
(29 feet x 8.0 psi/100 feet) . . . . . . . . . . . . . . . . .2.3 psi
7 feet of 1-3/8" OD, type “L” copper tubing (horizontal)
(7 feet x 2.8 psi/100 feet) . . . . . . . . . . . . . . . . . . 0.2 psi
Fitting* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.5 psi
Vapor Line Pressure Drop = 3.0 psi
*Determine the pressure drop of the fittings for each installation - DO NOT use
the estimated values as shown in the above examples.
Although longer vapor lines are permissible, friction
losses exceeding 3 psi (2°F) will reduce system capac-
ity in both the cooling and heating cycles.
SERVICE VALVES
These outdoor units have both vapor and liquid line
service valves.
Both valves are shipped from the factory front-seated
and closed with the valve stem in the maximum clock-
wise position.
These service valves are the back-seating type and
have a 1/4" male flare access port for evacuating and
charging the system.
FIGURE 6 - FIELD PIPING DIAGRAMS
(Cooling/Heating Refrigerant Flow)
TABLE 5: VAPOR LINES
System
Model
Refrigerant
Flow Rate,
1
(Lbs/Min)
1.
Based on Refrigerant-22 at the nominal cooling capacity of the system, a
vapor temperature of 40ºF and a liquid temperature of 105ºF. Since refriger-
ant flow rates will be a little lower at the nominal heating capacity of each sys-
tem, vapor line friction loss should always be based on cooling operation.
Type “L”
Copper Tubing
(In. OD)
Friction
Loss,
2
,
3
(PSI/100 Ft.)
2.
Although vapor lines should be sized for a friction loss equivalent to a 2ºF
change in saturation temperature (or approximately 3 psi), sizing the lines for
the proper return of oil is more important.
3.
These friction losses do not include any allowance for fittings. Only use a
1-1/8” riser when the indoor unit is above the outdoor unit.
EF-10
30.0
1-1/8
4.7
1-3/8
1.6
TABLE 6: REFRIGERANT LINE CHARGE
1
1.
Charges are based on 40ºF suction temperature and 105ºF liquid tempera-
ture.
Refrigerant
Line
2
2.
Type “L” copper tubing.
Line Size,
OD (In.)
Refrigerant Charge
(Lb/Ft)
Liquid
5/8
0.113
Vapor
1-1/8
0.013
1-3/8
