Use hard drawn copper tubing where no appreciableamountof
bending around pipes or other obstructions is necessary. Use
long radius ells wherever possible with one exception - small
radius ells for the traps in all vapor risers. If soft copper 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.
Braze all copper to copper joints with Silfos-5 or equivalent
brazing material. Do not use soft solder.
Insulate all vapor lines with a minimum of 1/2" ARMA-FLEX or
equal. Liquid lines exposed to direct sunlight and/or high tem-
peratures 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.
Never exceed the maximum line length listed in Table 1.
LINE SIZING
The following factors should be considered when locating the
indoor and outdoor units and when sizing the refrigerant lines
for a split heat pump system. Refer to Figure 5.
THE LIQUID LINE - The vertical rise should never exceed 50
feet because liquid refrigerant will lose 0.5 psi of static head for
each vertical foot.
The total pressure loss for a field-installed liquid line should
never exceed 40 psi because the liquid refrigerant could flash
before it reaches the expansion valve. This flashing will not
only cause erratic valve operation and poor system perform-
ance, but could also damage the expansion valve.
Total pressure loss includes the static head loss explained
above plus the friction losses due to the length of the line (Table
4) and number of fittings in the line.
When the indoor unit is above the outdoor unit, the friction loss
through the 1-1/8" OD vapor riser will be more of a limiting fac-
tor than the loss of static head in the liquid riser. See Example
#3 and #4 for the VAPOR LINE.
THE VAPOR LINE - A vapor line should not only be sized for a
friction loss of 3 psi (2
°
F) but also for the proper return of oil to
the compressor during both the cooling and heating cycles.
Friction loss should always be based on cooling operation be-
cause refrigerant flow rates will be greater during the cooling
cycle than during the heating cycle.
Oil return will be critical during:
1.
The cooling cycle when the outdoor unit is above the indoor
unit (detail 1 of Figure 5).
2.
The heating cycle when the indoor unit is above the outdoor
unit (detail 4 of Figure 5).
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 dur-
ing the heating cycle.
When 1-1/8" OD tubing must be used for the riser, the maxi-
mum length for the vapor line will be greatly reduced as shown
in the following examples.
EXAMPLES:
#1 - 7-1/2 Ton System
125 feet of 1-3/8" OD, type “L” copper tubing
(125 feet x 1.6 psi/100 feet) ...........................................2.0 psi
Fitting*....................................................................................0.4 psi
Vapor Line Pressure Drop = 2.4 psi
#2 - 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
#3 - 7-1/2 Ton System
51 feet of 1-1/8" OD, type “L” copper tubing (vertical)
(51 feet x 4.7 psi/100 feet) .............................................2.4 psi
6 feet of 1-3/8" OD, type “L” copper tubing (horizontal)
(6 feet x 1.6 psi/100 feet) ...............................................0.1 psi
Fitting*....................................................................................0.5 psi
Vapor Line Pressure Drop = 3.0 psi
#4 - 10 Ton System
29 feet of 1-1/8" OD, type “L” copper tubing (vertical)
Unitary Products Group
7
035-15410-002-B-0404
System
Model
Refrigerant
Flow Rate,
1
(Lbs/Min)
Type L
Copper
Tubing,
(In. OD)
Pressure Drop
3
Friction,
2
(PSI/100 Ft)
Vertical
Rise
(PSI/Ft)
EFB090/FEH090
22.5
5/8
3.5
0.5
EFB120/FEH120
30.0
5/8
5.8
0.5
1
Based on Refrigerant-22 at the nominal cooling capacity of the system, a liquid temperature
of 105
°
F and a vapor temperature of 40
°
F. Since refrigerant flow rates will be a little lower at
the nominal heating capacity of each system, liquid line friction loss should always be based
on cooling operation.
2
These friction losses do not include any allowance for fittings.
3
The total pressure drop of the liquid line for both friction and vertical rise must not exceed 40
PSI. If the pressure drop exceeds 40 PSI, the liquid refrigerant could flash before it reaches
the expansion valve. This flashing will not only cause erratic valve operation and poor system
performance, but could also damage the expansion valve.
TABLE 4
- LIQUID LINES
FIG. 5
- FIELD PIPING DIAGRAMS
(Cooling/Heating Refrigerant Flow)
